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There are several forms of kava (Piper methysticum) products available for human consumption, and many factors are known to influence their chemical compositions and therefore their pharmacological properties. Because of the increased popularity of kava intake, a rigorous characterization of their content diversity is prerequisite, particularly due to its known potential to cause hepatotoxicity. To understand the composition diversity of kavalactones and flavokavains in commercial kava products, we developed a UPLC-MS/MS-based analytical method for the quantification of six kavalactones (kavain, dihydrokavain, methysticin, dihydromethysticin, yangonin and desmethoxyyangonin) and two flavokavains (flavokavains A and B) and analyzed their contents in 28 different kava products in the form of capsules, tinctures, traditional aqueous suspensions and dried powders. Our results demonstrated a great variation in terms of the total and relative abundance of the analyzed kavalactones and flavokavains among the analyzed kava preparations. More importantly, the kavalactone abundance in the product label could differ up to 90% from our experimental measurements. Therefore, more rigorous and comprehensive quality control of kava products is required with respect to the content of individual kavalactones and flavokavains. Accurate content information is essential to understand the pharmacological properties and safety of different kava products.

Kava (Piper methysticum Forst) is a popular and favorable edible medicinal herb which was traditionally used to prepare a nonfermented beverage with relaxant beneficial for both social and recreational purposes. Numerous studies conducted on kava have confirmed the presence of kavalactones and flavokawains, two major groups of bioactive ingredients, in this miraculous natural plant. Expectedly, both kavalactone and flavokawain components exhibited potent antianxiety and anticancer activities, and their structure-activity relationships were also revealed. However, dozens of clinical data revealed the hepatotoxicity effect which is indirectly or directly associated with kava consumption, and most of the evidence currently seems to point the compounds of flavokawains in kava were responsible. Therefore, our aim is to conduct a systematic review of kavalactones and flavokawains in kava including their biological activities, structure-activity relationships, and toxicities, and as a result of our systematic investigations, suggestions on kava and its compounds are supplied for future research.

Kavain, kavalactone, present in Piper methysticum exhibits anticonvulsive, analgesic, anxiolytic, antiepileptic, antithrombotic, anti-inflammatory and antioxidant properties. Given its importance, ...

Kava, the rhizomes and roots of Piper methysticum Forst, is a popular edible medicinal herb traditionally used to prepare beverages for anxiety reduction. Since the German kava ban has been lifted by the court, the quality evaluation is particularly important for its application, especially the flavokawains which were believed to be responsible for hepatotoxicity. Now, by employing two different standard references and four different methods to calculate the relative correction factors, eight different quantitative analyses of multicomponents by single-marker methods have been developed for the simultaneous determination of eight major kavalactones and flavokawains in kava. The low standard method difference on quantitative measurement of the compounds among the external standard method and ours confirmed the reliability of the mentioned methods. A radar plot clearly illustrated that the contents of dihydrokavain and kavain were higher, whereas flavokawains A and B were lower in different kava samples. Only one of eight samples did not detect flavokawains that may be related to hepatotoxicity. In summary, by using different agents as an internal standard reference, the developed methods were believed as a powerful analytical tool not only for the qualitative and quantitative of kava constituents but also for the other multicomponents when authentic standard substances were unavailable.

Bone loss and bone-related disease are associated with the deregulation of osteoclast function, and therefore agents that affect osteoclastogenesis have attracted attention. The purpose of the present study was to discover modified kavalactone analogs as potential anti-osteoclastogenic agents. We assessed the effect of 26 analogs on osteoclast differentiation in vitro. The most potent compound, (E)-6-(2-fluorostyryl)-4-methoxy-2H-pyran-2-one (22), suppressed receptor activator of nuclear factor-κB ligand (RANKL)-induced osteoclastogenic differentiation of RAW264 cells with IC50 values of 4.3 µM. A partial structure-activity relationship study revealed the importance of fluorine and its position within the 5,6-dehydrokawain skeleton. The results of a pit formation assay suggested that compound 22 prevents osteoclastic bone resorption by inhibiting osteoclastogenesis. Moreover, compound 22 downregulated mRNA expression levels of RANKL-induced nuclear factor of activated T cells c1 (NFATc1) and osteoclastogenesis-related genes. These results suggest that (E)-6-(2-fluorostyryl)-4-methoxy-2H-pyran-2-one scaffold could lead to the identification of new anti-resorptive agents.

A new kavalactone dimer, named kavalactone A (1), and three known compounds, desmethoxyyangonin (2), yangonin (3), and 11-methoxyyangonin (4), were isolated from the leaves of Piper methysticum (kava). Their structures were determined by spectroscopic methods, mainly 1D and 2D NMR and mass spectrpscopic data. Primary bioassays showed that compound 3 had very strong cytotoxicity against A549 and NCI-H460 Cells with IC50 values of 13.6 and 13.7 μg/mL, respectively, compound 2 had moderate cytotoxicity against A549 and NCI-H460 cells (with IC50 values of 35.8 and 37.6 μg/mL, respectively), and compounds 1 and 4 had very weak cytotoxicity against A549 and NCI-H460 cells.

Introduction Dried extracts of Piper methysticum G. Forst, also known as kava, has been widely used due to its anxiolytic and sedative properties. In order to assure the quality of these extracts, it is essential to accurately quantify kavalactones, known as the active principle. Objectives To develop and validate an analytical method for the simultaneous quantification of six major kavalactones (kavain, dihydrokavain, methysticin, dihydromethysticin, yangonin and demethoxyyangonin) in kava extracts, comparing multi-standards and single standard validation approaches. Material and methods Separation was performed using a C18 column, water/methanol/acetonitrile/2-propanol (66:07:09:18 v/v/v/v) and detection at 245 and 350 nm. A full method validation was performed, employing analytical standards for each compound. Commercial kava dried extracts were assayed and the results obtained using the method validated for six kavalactone standards were compared with those obtained when only kavain was used as standard. Results Baseline resolution for all kavalactones was obtained in short run time (15 min). Although the total kavalactone content varied between samples, a similar distribution profile was observed. When the method validated with all six analytical standards was compared to the calibration using only kavain standard, kavalactone contents were considerably different (from 7.57 to 36.53%). Conclusion The obtained results demonstrate the importance of a validated method using individual kavalactone standards for the effective quality control of kava extracts. In a next step, the method needs to be adapted to also include flavokavin B (FKB), as an important authentication marker to distinguish between the accepted variety "noble Kava" and the toxic "two-day Kava".

Background Kava is an important neuroactive medicinal plant. While kava has a large global consumer footprint for its clinical and recreational use, factors related to its use lack standardization and the tissue-specific metabolite profile of its neuroactive constituents is not well understood. Results Here we characterized the metabolomic profile and spatio-temporal characteristics of tissues from the roots and stems using cross-platform metabolomics and a 3D imaging approach. Gas chromatography–mass spectrometry and liquid chromatography–mass spectrometry revealed the highest content of kavalactones in crown root peels and lateral roots. Infrared matrix-assisted laser desorption electrospray ionization (IR-MALDESI) imaging revealed a unique tissue-specific presence of each target kavalactone. X-ray micro-computed tomography analysis demonstrated that lateral roots have morphological characteristics suitable for synthesis of the highest content of kavalactones. Conclusions These results provide mechanistic insights into the social and clinical practice of the use of only peeled roots by linking specific tissue characteristics to concentrations of neuroactive compounds.

Introduction There is increasing evidence for the involvement of chronic inflammation and oxidative stress in the pathogenesis of Alzheimer's disease (AD). Nuclear factor erythroid 2-related factor 2 (Nrf2) is an anti-inflammatory transcription factor that regulates the oxidative stress defense. Our previous experiments demonstrated that kavalactones protect neuronal cells against Amyloid β (Aβ)-induced oxidative stress in vitro by Nrf2 pathway activation. Here, we tested an in vivo kavalactone treatment in a mouse model of AD. Methods The kavalactone methysticin was administered once a week for a period of 6 months to 6 month old transgenic APP/Psen1 mice by oral gavage. Nrf2 pathway activation was measured by methysticin treatment of ARE-luciferase mice, by qPCR of Nrf2-target genes and immunohistochemical detection of Nrf2. Aβ burden was analyzed by CongoRed staining, immunofluorescent detection and ELISA. Neuroinflammation was assessed by immunohistochemical stainings for microglia and astrocytes. Pro-inflammatory cytokines in the hippocampus was determined by Luminex multi-plex assays. The hippocampal oxidative damage was detected by oxyblot technique and immunohistochemical staining against DT3 and 4-HNE. The cognitive ability of mice was evaluated using Morris water maze. Results Methysticin treatment activated the Nrf2 pathway in the hippocampus and cortex of mice. The Aβ deposition in brains of methysticin-treated APP/Psen1 mice was not altered compared to untreated mice. However, methysticin treatment significantly reduced microgliosis, astrogliosis and secretion of the pro-inflammatory cytokines TNF-α and IL-17A. In addition, the oxidative damage of hippocampi from APP/Psen1 mice was reduced by methysticin treatment. Most importantly, methysticin treatment significantly attenuated the long-term memory decline of APP/Psen1 mice. Conclusion In summary, these findings show that methysticin administration activates the Nrf2 pathway and reduces neuroinflammation, hippocampal oxidative damage and memory loss in a mouse model of AD. Therefore, kavalactones might be suitable candidates to serve as lead compounds for the development of a new class of neuroprotective drugs., Highlights • Methysticin activates the Nrf2/ARE system in the hippocampus of mice. • Methysticin protects AD mice against oxidative stress and associated neuroinflammation due to Nrf2 activation. • Methysticin improves long-term memory impairment in this mouse model of AD.

The present study aimed at evaluating the potential of diethyl ether extracts UV/visible (UV/vis) absorbance for assessing the suitability of commercial lots of kava (Piper methysticum). The UV/vis absorption spectra of diethyl ether root extracts of 15 cultivars clustered them into three groups in parallel to their known genetic relatedness and their chemical composition determined by GC–MS and LC–MS analyses. Absorption peaks at 250 nm and 290 nm respectively corresponded to kavain, the most health-promoting kavalactone, and dihydromethysticin a non-desirable kavalactone. The absorbance peak at 340–350 nm reflected the yellow coloration of the extract, which was mainly due to the undesirable flavokavins, desmethoxyyangonin and yangonin. Ratios of absorbance values at 250 nm and 290 nm significantly differentiated all three groups of cultivars, namely 'noble' which provide health benefits from 'two-day' and 'wichmannii' that are health damaging. These results provide a robust and rapid colorimetric test for routine control of a critical aspect of the quality of kava batches. (Resume d'auteur)

Alpinia zerumbet (Pers.) B.L.Burtt & R.M.Sm. (Zingiberaceae) is a perennial plant native to the East Indies and is widely distributed in South America, Oceania, and Asia. The mature fruits of the plant have been used in traditional medicine in China. In this study, we compared the chemical constituents in the methanol extracts of the leaves, the placenta, the pericarps, and the seeds obtained from the same plant using LC-MS, and we examined the NO inhibitory activities of the respective extracts and the isolated compounds. As a result of LC-MS analyses, kavalactone derivatives (1-6) were detected in the methanol extracts of the leaves, placenta, and pericarps. Of these, compound 6 was identified as a new asymmetrical cyclobutane dimer of 5,6-dehydrokawain. Quantitative analysis showed that the total amounts of kavalactone derivatives were highest in the methanol extract of the pericarps. Moreover, the results of measurements of the anti-inflammatory activity revealed that the pericarps extract showed the strongest activity. The compounds responsible for the anti-inflammatory activity of the extracts from A. zerumbet were identified. Of these, five were known kavalactone derivatives and one was a new kavalactone derivative (aniba dimer C). The results showed that the pericarps of A. zerumbet are a rich source of kavalactone derivatives, and that the pericarps of A. zerumbet can be utilized as an important medicinal resource.

Background: Epidemiological studies indicate there is low incidence of colon cancer in the South Pacific islands, including Fiji, West Samoa, and Vanuatu. Cancer incidence has been shown to be inversely associated with kava ( Piper methysticum G. Forst.) ingestion. Hypothesis/Purpose: Kava prepared traditionally will inhibit the growth of human cancer cells. This investigation entails preparation and analysis of kava extracts and study of the growth inhibitory activity of the extracts, alone and combined with hibiscus. Study Design: We will prepare kava as in Micronesia – as a water extract, high in particulate content, alone or combined with sea hibiscus ( Hibiscus tiliaceus L.) – and examine the components and growth inhibitory activity. Methods: We obtained ground kava prepared in the traditional way from lateral roots and sea hibiscus mucilage and sap from different sources in Micronesia, and prepared water extracts (unfiltered, as well as filtered, since in traditional use the kava beverage contains a high particulate content) and partitions. We used the MTT assay to determine the growth inhibitory activity of the preparations on colon and breast cancer cells and nonmalignant intestinal epithelial cells. LC-MS analysis was used to examine the components of the kava and sea hibiscus extracts and partitions. Results: Traditional preparations of kava inhibit the growth of breast and colon cancer cells. Among the kava preparations, the order of decreasing activity was Fiji(2), Fiji(1), Hawaii; the unfiltered preparations from Fiji were more active than the filtered. Phytochemical analysis indicated that filtering reduced most kavalactone and chalcone content. For example, for Fiji(2), the ratio of dihydromethysticin in filtered/unfiltered kava was 0.01. Thus, for the extracts from Fiji, growth inhibitory activity correlates with the content of these compounds. Unfiltered and filtered kava from Fiji(1) were more active on malignant than nonmalignant intestinal epithelial cells. Since kava is prepared in Micronesia by squeezing the extract through sea hibiscus bark, we assayed the growth inhibitory activity of combinations of kava and sea hibiscus sap and found that sea hibiscus enhanced the growth inhibitory effect of kava. Conclusion: Our results show that traditional kava, alone or combined with sea hibiscus, displays activity against human cancer cells and indicate it will be worthwhile to develop and further analyze these preparations to prevent and treat colon and other cancers. Our findings suggest it is important to examine the activity of plants in the form that people consume them.

Kava extract, an aqueous rhizome emulsion of the plant Piper methysticum, has been used for centuries by Pacific Islanders as a ceremonial beverage, and has been sold as an anxiolytic agent for some decades. Kavalactones are a major constituent of kava extract. In a previous investigation, we had identified three kavalactones that inhibit larval development of Haemonchus contortus in an in vitro-bioassay. In the present study, we synthesized two kavalactones, desmethoxyyangonin and yangonin, as well as 17 analogues thereof, and evaluated their anthelmintic activities using the same bioassay as employed previously. Structure activity relationship (SAR) studies showed that a 4-substituent on the pendant aryl ring was required for activity. In particular, compounds with 4-trifluoromethoxy, 4-difluoromethoxy, 4-phenoxy, and 4-N-morpholine substitutions had anthelmintic activities (IC50 values in the range of 1.9 to 8.9 &micro, M) that were greater than either of the parent natural products&mdash, desmethoxyyangonin (IC50 of 37.1 &micro, M) and yangonin (IC50 of 15.0 &micro, M). The synthesized analogues did not exhibit toxicity on HepG2 human hepatoma cells in vitro at concentrations of up to 40 &micro, M. These findings confirm the previously-identified kavalactone scaffold as a promising chemotype for new anthelmintics and provide a basis for a detailed SAR investigation focused on developing a novel anthelmintic agent.

Ethnopharmacological relevance Kava and kava extracts have shown great potential as a way to minimize anxiety-associated symptoms and to help alleviate pain. Hepatoxicity has been associated with the consumption of kava products. The chemical compounds, kavalactones (KL) and flavokavains (FK) have been implicated in kava’s psychotropic and possible hepatotoxic properties. Aim of the study To investigate the kavalactone and flavokavain content and in vitro toxicity of KAVOA™, a supercritical carbon dioxide extraction (SFE) of kava. Materials and methods Kavalactone and flavokavain content of SFE kava and noble kava root were determined following extraction in acetone, cell culture media, and water using ultra high-performance liquid chromatography (UHPLC). Using water extractions of the kava products, the cell viability and toxicity on the human hepatocellular carcinoma cell line (HepG2) were determined using luminescent and fluorescent assays, respectively. The half maximal inhibitory concentration (IC50) of the SFE kava and noble kava root, extracted in cell culture media, were determined utilizing a luminescent cell viability assay. Results Quantification of the KAVOA™, a SFE extract of kava and kava root showed similar profiles of kavalactone and flavokavain content. Water extracted SFE and root kava did not show a negative impact on cell viability and toxicity when compared to the vehicle control treated cells. IC50 values were determined for the SFE kava and kava root extracted in cell culture media in respect to cell viability, 78.63 and 47.65 µg/mL, respectively. Conclusions KAVOA™, a supercritical carbon dioxide extract of kava displays a similar kavalactone profile to a noble variety of kava. In relation to total kavalactone content, KAVOA™ also has a lower content of the cytotoxic compound FKB. Aqueous extractions of KAVOA™ and noble kava root had no significant negative impact on cell viability and toxicity on HepG2 cells when compared to vehicle controlled treated cells. Results indicate KAVOA™ demonstrates a similar in vitro safety profile to that of noble kava root when experiments are normalized to kavalactone content.

Kavalactones are a group of compounds found in kava, a beverage or extract prepared from the rhizome of the kava plant (Piper methysticum). Traditionally kava extracts have been used for their anxiolytic and sedative properties. Sales of kava extracts were severely restricted or prohibited in European countries in 2002 following several cases of serious hepatotoxicity. Here we report a case where high concentrations of kavalactones and ethanol were detected in post mortem femoral blood. An injection needle with a 10-mL syringe containing 7.5 mL of slightly yellowish liquid was found next to the victim, and there were numerous needle prints on both lower arms following the venous tracks. No evidence of other cause of death was found in the medico-legal investigation. The case was therefore classified as suicide using an injection of kavalactones intravenously together with alcohol poisoning.

Three new dimeric kavalactones, designated as diyangonins A–C (1–3), along with two known analogs were isolated from the roots of Piper methysticum. Their structures were elucidated by means of extensive analysis of their 1D, 2D NMR, and mass spectroscopic data. All these dimers possess a skeleton featuring a cyclobutane ring connecting two kavalactone units in head-to-tail or head-to-head mode. Compounds 1–5 were evaluated for their cytotoxic activities against human tumor cell lines.

Consumption of kava (Piper methysticum Forst) has been linked to reduced cancer risk in the South Pacific Islands. Kavalactones are major bioactive components in kava root extracts, which have recently demonstrated anti-cancer activities. However, molecular mechanisms of kavalactones' anti-cancer action remain largely unknown. We have identified two kavalactones, yangonin and 5' 6'-dehydrokawain, as potent inducers of autophagic cell death in bladder cancer cells. The effect of yangonin inducing autophagy is associated with increased expression of beclin and ATG5. In addition, yangonin increases the expression of LKB1 and decreases the phosphorylation of Akt, PRAS40, rpS6, p70S6K and 4E-BP1, leading to increased binding of 4E-BP1 to m7 GTP. The growth inhibitory effects of yangonin were attenuated inTSC1 or LKB1 knockout mouse embryonic fibroblasts, suggesting that TSC1 and LKB1 expression may contribute to optimal growth inhibition by yangonin. Furthermore, yangonin reduces the viability of bladder cancer cell lines derived from different stages of human bladder cancer, and acts synergistically with apoptosis-inducing agents such as docetaxel and flavokawain A. Our results support a novel anti-bladder cancer mechanism by yangonin and further studies are needed to assess the potential use of yangonin for bladder cancer prevention and treatment.

Anxiolytic kava products have been associated with rare but severe hepatotoxicity in humans. This adverse potential has never been captured in animal models, and the responsible compound(s) remains to be determined. The lack of such knowledge greatly hinders the preparation of a safer kava product and limits its beneficial applications. In this study we evaluated the toxicity of kava as a single entity or in combination with acetaminophen (APAP) in C57BL/6 mice. Kava alone revealed no adverse effects for long-term usage even at a dose of 500 mg/kg bodyweight. On the contrary a three-day kava pretreatment potentiated APAP-induced hepatotoxicity, resulted in an increase in serum ALT and AST, and increased severity of liver lesions. Chalcone-based flavokawains A (FKA) and B (FKB) in kava recapitulated its hepatotoxic synergism with APAP while dihydromethysticin (DHM, a representative kavalactone and a potential lung cancer chemopreventive agent) had no such effect. These results, for the first time, demonstrate the hepatotoxic risk of kava and its chalcone-based FKA and FKB in vivo and suggest that herb–drug interaction may account for the rare hepatotoxicity associated with anxiolytic kava usage in humans.

This study was aimed to investigate the effect of continuous flow microwave heating on the reduction of microorganisms in kava juice to extend the shelf life. Chemical and microbial properties of treated juices were analyzed using key parameters such as microbial counts, kavalactones, and pectin methylesterase activities. The microbial population was reduced from 3.3×106 to 5×105, 8×103, and 4.5×102 CFU/mL at 41.4, 52.3, and 65.2°C, respectively. The amounts of kavalactones such as kavain (K), demethoxyyangonin (DMY), and yangonin (Y) were kept constant or increased after pasteurization at different treatment temperatures. The effect of microwave heating on the pectin methylesterase activities decreased significantly from 83 to 34% by increasing the temperature values from 41.4 to 65.2°C, enhancing juice cloud stability. The developed pasteurization technique is expected to deliver the adequate lethal effect to the kava juice without major deterioration of food quality.

The South Pacific islanders have consumed kava beverage for thousands of years. The quality of kava and kava beverage is evaluated through determination of the content of six major kavalactones including methysticin, dihydromethysticin, kavain, dihydrokavain, yangonin and desmethoxyyangonin. In this study, we determined contents of kavalactones in and chemotype of kava beverages prepared from roots and rhizomes of Isa and Mahakea varieties and extraction efficiency of five different solvents including hexane, acetone, methanol, ethanol and ethyl acetate. The six major kavalactones were detected in all kava beverages with these five solvents. Different solvents had different extraction efficiencies for kavalactones from the lyophilized kava preparations. The contents of kavalactones in the extracts with acetone, ethanol, and methanol did not differ significantly. Ethanol had the highest extraction efficiency for the six major kavalactones whereas hexane gave the lowest extraction efficiency.

An imbalance between bone resorption by osteoclasts and bone formation by osteoblasts can cause bone loss and bone-related disease. In a previous search for natural products that increase osteogenic activity, we found that 5,6-dehydrokawain (1) from Alpinia zerumbet promotes osteoblastogenesis. In this study, we synthesized and evaluated series of 5,6-dehydrokawain analogs. Our structure-activity relationships revealed that alkylation of para or meta position of aromatic ring of 1 promote osteogenic activity. Among the potential analogs we synthesized, (E)-6-(4-Ethylstyryl)-4-methoxy-2H-pyran-2-one (14) and (E)-6-(4-Butylstyryl)-4-methoxy-2H-pyran-2-one (21) both significantly up-regulated Runx2 and Osterix mRNA expression at 10µM. These osteogenic activities could be mediated by bone morphogenetic protein (BMP) and activation of p38 MAPK signaling pathways. Compounds 14 and 21 also inhibited RANKL-induced osteoclast differentiation of RAW264 cells. These results indicated that novel 5,6-dehydrokawain analogs not only increase osteogenic activity but also inhibit osteoclast differentiation, and could be potential lead compounds for the development of anti-osteoporosis agents.

Three new kavalactone dimers, designated as yangonindimers A-C (1–3), along with one known analogue were isolated from the roots of Piper methysticum. Their structures were elucidated via extensive analysis of their 1D, 2D NMR and mass spectroscopic data. All these dimers possess a skeleton featuring a cyclobutane ring connecting two kavalactone units. Compounds 1–4 were evaluated for their cytotoxic activities against human tumour cell lines NCI-H46, SW480 and HepG2, but none showed significant activity.

To investigate the possible interactions between kavalactone-based molecules and proteins of the endocannabinoid system and provide novel and synthetically accessible structural scaffolds for the design of cannabinoid receptor ligands sharing pharmacological properties with kavapyrones, a preliminary SAR analysis was performed on five commercially available natural kavalactones and nine kavalactone-analogues properly synthesized. These compounds were investigated for assessing their cannabinoid receptor binding affinity and capability of inhibiting the activity of the two major metabolic enzymes of the endocannabinoid system, fatty acid amide hydrolase (FAAH) and monoacylglycerol lipase (MAGL). Among the molecules tested, only yangonin exhibited affinity for the human recombinant CB₁ receptor with a K(i)=0.72 μM and selectivity vs. the CB₂ receptor (K(i)>10 μM). None of the compounds exhibited strong inhibitory effects on the two enzymes analyzed. The CB₁ receptor affinity of yangonin suggests that the endocannabinoid system might contribute to the complex human psychopharmacology of the traditional kava drink and the anxiolytic preparations obtained from the kava plant.

Metabolic pathways for kavalactone metabolism in humans and rats have been identified, but more detailed description of the enzyme kinetics involved is lacking. The disposition profiles of three of the six major kavalactones (kavain, methysticin and desmethoxyyangonin) and their respective metabolites (p-hydroxykavain, m,p-dihydroxykavain and p-hydroxy-5,6-dehydrokavain) were examined in the perfusate and bile of the isolated perfused rat liver. The metabolism of the kavalactones is first-order in nature with similar decay half-lives. p-Hydroxykavain and m,p-dihydroxykavain were the only metabolites detected in the perfusate. Kavalactone biliary excretion was negligible.

The specific CYP enzymes involved in kavalactone (KLT) metabolism and their kinetics have not been fully examined. This study used rat liver microsomes (RLM) to determine kavain (KA), methysticin (MTS) and desmethoxyyangonin (DMY) enzyme kinetic parameters, to elucidate the major CYP450 isoforms involved in KLT metabolism and to examine gender differences in KLT metabolism. Formation of the major KLT metabolites was first-order, consistent with classic enzyme kinetics. In both male and female RLM, clotrimazole (CLO) was the most potent inhibitor of KA and MTS metabolism. This suggests CYP3A1/3A23 (females) and CYP3A2 (males) are the main isoenzymes involved in the metabolism of these KLTs in rats, while the roles of CYP1A2, -2 C6, -2 C9, -2E1 and -3A4 are limited. Desmethoxyyangonin metabolism was equally inhibited by cimetidine (CIM) and CLO in females, and CIM and nortriptyline in males. This implies that DMY metabolism involves CYP2C6 and CYP2C11 in males, and CPY2C12 in females. CYP3A1/3A23 may also be involved in females. Copyright © 2011 John Wiley & Sons, Ltd.

A number of studies have identified differential kavalactone activity against a variety of molecular targets, including P-glycoprotein (Pgp), platelet monoamine oxidase (MAO-B), transcription factor binding domains, pregnane X (PXR) and GABA receptors, and cytochrome P450 and cyclo-oxygenase (COX) enzymes. The molecular structure of the kavalactones possesses a pharmacophore for several of these targets. In most cases, conformational stability is more significant than the substituents present. The analysis of these pharmacophores provides important insights for future medicinal chemistry-based approaches to kavalactone-type drugs.

Diabetes mellitus (DM) is a disease that is caused by a malfunction of carbohydrate metabolism, which plays an important role in the development of long-term diabetic complications. The excess glucose can be transformed to methylglyoxal (MG), a potential precursor of glycation. Glycation is a spontaneous non-enzymatic reaction that initially yields advanced glycation end-products (AGEs), which ultimately triggers several severe complications. Therefore, the inhibition of AGEs formation is the imperative approach for alleviating diabetic complications. The aim of this research was to investigate the glycation and &alpha, glucosidase inhibitory abilities of compounds isolated from fingerroot. The dichloromethane extract afforded three flavanones, two chalcones, two dihydrochalcones, and one kavalactone. Most of the isolated compounds showed higher inhibition effect against AGEs formation than aminoguanidine (AG). Subsequent evaluation in MG-trapping assay indicated that their trapping potency was relatively comparable to AG. Their structure-activity relationships (SAR) of MG-trapping activity were investigated using the comparison of the structures of flavonoids. In addition, pinocembrin displayed moderate &alpha, glucosidase inhibition against both maltase and sucrose, with IC50 values of 0.35 &plusmn, 0.021 and 0.39 &plusmn, 0.020 mM, respectively.

Piper methysticum (kava) root is known to possess promising weed suppressing activity. The present study was conducted to search for potent plant growth inhibitors from the root of this medicinal pepper plant. The ethyl acetate (EtOAc) extract exhibited the strongest reduction on growth of Raphanus sativus (radish) (IC50 shoot and root growth = 172.00 and 51.31 &micro, g/mL respectively) among solvent extracts. From this active extract, nine potent growth inhibitors involved in the inhibitory activities of P. methysticum root were isolated, purified and characterized by column chromatography (CC), gas chromatography-mass spectrometry (GC-MS), electrospray ionization-mass spectrometry (ESI-MS) and nuclear magnetic resonance (NMR). The six fractions purified by CC included two flavanones: 5-hydroxy-4&prime, 7-dimethoxyflavanone (C1) and 5,7-dihydroxy-4&prime, methoxy-6,8-dimethylflavanone (matteucinol, C2) and six kavalactones: 5,6-dehydro-kavain (C3), a mixture of kavain and yagonin (C4), yagonin (C5) and dihydro-5,6-dehydrokavain, 7,8-dihydrokavain, dihydromethysticin and methysticin (C6). The amounts of 5-hydroxy-4&prime, 7-dimethoxyflavanone, matteucinol, 5,6-dehydrokavain and yangonin were 0.76, 2.50, 2.75 and 2.09 mg/g dry weight (DW), respectively. The two flavanones C1 and C2 exhibited the strongest inhibition on shoot elongation (IC50 = 120.22 and 248.03 &micro, g/mL, respectively), whilst the two kavalactone mixtures C4 and C6 showed the highest suppression on root growth of R. sativus (IC50 = 7.70 and 15.67 &micro, g/mL, respectively). This study was the first to report the purification and inhibitory activities of the two flavanones 5-hydroxy-4&prime, 7-dimethoxyflavanone and matteucinol in P. methysticum root. The isolated constituents from P. methysticum root including the flavanones C1 and C2 and the mixtures C4 and C6 may possess distinct modes of action on plant growth. Findings of this study highlighted that the combinations of hexane-ethyl acetate by 9:1 and 8:2 ratios successfully purified flavanones and kavalactones in P. methysticum root.

Oxidative stress is involved in the pathogenesis of neurodegenerative disorders such as Parkinson's and Alzheimer's diseases. Natural kavalactones isolated from Piper methysticum (Piperaceae) are capable of activating the Nrf2/ARE (antioxidant response element) pathway and thus enhancing the expression of phase II antioxidant enzymes such as heme oxygenase-1 (HO-1). In an attempt to identify kavalactone derivatives that are more potent in Nrf2/ARE activation than natural compounds, we synthesized a series of chemically-modified kavalactones and studied their effects on the ARE enhancer activity in rat pheochromocytoma PC12 cells. Among 81 compounds tested, a kavalactone derivative, 2',6'-dichloro-5-methoxymethyl-5,6-dehydrokawain [(E)-6-(2',6'-dichlorostyryl)-4-methoxy-5-(methoxymethyl)-2H-pyran-2-one] (1), exhibited the strongest ARE enhancer activity. The ARE activation and HO-1 protein induction by the compound 1 were higher than those by natural kavalactones. The compound did not affect cell viability and induced expression of various phase II enzymes. Nuclear translocation of Nrf2 after treatment with 1 was preceded by phosphorylation of ERK1/2 and p38. The compound transiently increased intracellular ROS levels. Finally, pretreatment with the compound ameliorated H(2)O(2)-induced cell death, which was associated with increased expression of HO-1. These results suggest that the compound 1 protects against oxidative stress-induced neuronal cell death via a preconditioning effect on the Nrf2/ARE activation.

Two new diarylheptanoids, katsumains A (1) and B (2), and one new kavalactone, katsumadain (3), together with the three known compounds (4E,6E)-1,7-diphenylhepta-4,6-dien-3-one (4), (5R,6E)-1,7-diphenyl-5-hydroxyhept-6-en-3-one (5), and cardamonin (6), were isolated from the seeds of Alpinia katsumadaiHayata. Their structures were elucidated mainly by spectroscopic methods (1D- and 2D-NMR) and by mass spectrometry (HR-ESI-MS). Besides, the erroneous nomenclatures for (+)-linderatin and (+)-neolinderatin as given in [10] [11] were corrected to be 2′,4′,6′-trihydroxy-3′-[(3R,4R)-4-isopropyl-1-methylcyclohex-1-en-3-yl]dihydrochalcone for (+)-linderatin and 2′,4′,6′-trihydroxy-3′,5′-bis[(3R,4R)-4-isopropyl-1-methylcyclohex-1-en-3-yl]dihydrochalcone for (+)-neolinderatin, respectively.

Kava (Piper methysticum) is a member of the pepper family and has been cultivated by South Pacific islanders for centuries and used as a social and ceremonial drink. Traditionally, kava extracts are prepared by grinding or chewing the rhizome and mixing with water and coconut milk. The active constituents of kava are a group of approximately 18 compounds collectively referred to as kavalactones or kava pyrones. Kawain, dihydrokawain, methysticin, dihydromethysticin, yangonin, and desmethoxyyangonin are the six major kavalactones. Kava beverages and other preparations are known to be anxiolytic and are used for anxiety disorders. Dietary supplements containing the root of the kava shrub have been implicated in several cases of liver toxicity in humans, including several who required liver transplants after using kava supplements. In order to study the toxicity and mutagenicity, two commercial samples of kava, Kaviar and KavaPure, and the six pure kavalactones including both D-kawain and DL-kawain, were evaluated in L5178Y mouse lymphoma cells. Neither the kava samples nor the kavalactones induced a mutagenic response in the L5178Y mouse lymphoma mutation assay with the addition of human liver S9 activation.

Extracts of the pepper plant kava (Piper methysticum) are effective in alleviating anxiety in clinical trials. Despite the long-standing therapeutic interest in kava, the molecular target(s) of the pharmacologically active constituents, kavalactones have not been established. γ-Aminobutyric acid type A receptors (GABAARs) are assumed to be the in vivo molecular target of kavalactones based on data from binding assays, but evidence in support of a direct interaction between kavalactones and GABAARs is scarce and equivocal. In this study, we characterised the functional properties of the major anxiolytic kavalactone, kavain at human recombinant α1β2, β2γ2L, αxβ2γ2L (x = 1, 2, 3 and 5), α1βxγ2L (x = 1, 2 and 3) and α4β2δ GABAARs expressed in Xenopus oocytes using the two-electrode voltage clamp technique. We found that kavain positively modulated all receptors regardless of the subunit composition, but the degree of enhancement was greater at α4β2δ than at α1β2γ2L GABAARs. The modulatory effect of kavain was unaffected by flumazenil, indicating that kavain did not enhance GABAARs via the classical benzodiazepine binding site. The β3N265M point mutation which has been previously shown to profoundly decrease anaesthetic sensitivity, also diminished kavain-mediated potentiation. To our knowledge, this study is the first report of the functional characteristics of a single kavalactone at distinct GABAAR subtypes, and presents the first experimental evidence in support of a direct interaction between a kavalactone and GABAARs.

Kava (Piper methysticum Forst. f. ) is traditionally used as a beverage for relaxation in social occasions in South Pacific islands. This study was conducted to develop analytical methods for assessing kavalactone content in functional beverage products containing kava, as well as beverages prepared from kava roots by a traditional method involving infusion (mild extraction) with water. Samples of fruit-flavored beverages were prepared by solid-phase or liquid–liquid extraction to remove interfering substances and the major kavalactones (methysticin, dihydromethysticin, kavain, dihydrokavain, yangonin, and desmethoxyyangonin) were separated and identified by GC-FID and GC/EI-MS. A difference in kavalactone content was observed between the 2 commercial beverage products (37.03 compared with 0.044 mg per serving in 240 mL). Kava beverages prepared fresh by water infusion contained much higher levels of kavalactones than the commercial products as determined by a high-performance liquid chromatographic procedure. The results also demonstrated the isomerization of yangonin (Y) in an acidic aqueous solution with exposure to light, with the presence of cis-Y in a fruit-flavored beverage containing kava. The implications of the isomerization of Y on quality and safety aspects have yet to be evaluated. The analytical methods developed in this study are potentially applicable to kavalactone analysis in various nonalcoholic, noncarbonated beverages.

Reported adverse drug interactions with the popular herb kava have spurred investigation of the mechanisms by which kava could mediate these effects. In vivo and in vitro experiments were conducted to examine the effects of kava extract and individual kavalactones on cytochrome P450 (P450) and P-glycoprotein activity. The oral pharmacokinetics of the kavalactone, kawain (100 mg/kg), were determined in rats with and without coadministration of kava extract (256 mg/kg) to study the effect of the extract on drug disposition. Kawain was well absorbed, with >90% of the dose eliminated within 72 h, chiefly in urine. Compared with kawain alone, coadministration with kava extract caused a tripling of kawain AUC(0-8 h) and a doubling of C(max). However, a 7-day pretreatment with kava extract (256 mg /kg/day) had no effect on the pharmacokinetics of kawain administered on day 8. The 7-day pretreatment with kava extract only modestly induced hepatic P450 activities. The human hepatic microsomal P450s most strongly inhibited by kava extract (CYP2C9, CYP2C19, CYP2D6, CYP3A4) were inhibited to the same degree by a "composite" kava formulation composed of the six major kavalactones contained in the extract. K(i) values for the inhibition of CYP2C9 and CYP2C19 activities by methysticin, dihydromethysticin, and desmethoxyyangonin ranged from 5 to 10 microM. Kava extract and kavalactones (< or =9 microM) modestly stimulated P-glycoprotein ATPase activities. Taken together, the data indicate that kava can cause adverse drug reactions via inhibition of drug metabolism.

High speed countercurrent chromatography (HSCCC) was used to isolate the major kavalactones kavain, 7,8‐dihydrokavain, methysticin, 7,8‐dihydromethysticin, yangonin, and demethoxyyangonin. An ethanolic crude extract of kava root was subjected to HSCCC separation. Due to the presence of polymeric material, the sample load was limited. Hence, gel chromatography was applied in order to concentrate the kavalactones and to reduce the amount of polymers. The purified extract was again subjected to a HSCCC separation. A higher sample input was achieved, but only kavain and demethoxyyangonin were obtained in pure form. The remaining kavalactones eluted in three fractions, which needed to be further purified by preparative HPLC.

For centuries the South Pacific islanders have consumed kava (Piper methysticum) as a ceremonial intoxicating beverage. More recently, caplets of kava extracts have been commercialized for their anxiolytic and antidepressant activities. Several cases of hepatotoxicity have been reported following consumption of the commercial preparation whereas no serious health effects had been documented for the traditional beverage. A detailed comparison of commercial kava extracts (prepared in acetone, ethanol or methanol) and traditional kava (aqueous) reveals significant differences in the ratio of the major kavalactones. To show that these variations could lead to differences in biological activity, the extracts were compared for their inhibition of the major drug metabolizing P450 enzymes. In all cases (CYP3A4, CYP1A2, CYP2C9, and CYP2C19), the inhibition was more pronounced for the commercial preparation. Our results suggest that the variations in health effects reported for the kava extracts may result from the different preparation protocols used.

Kava-kava is a traditional beverage of the South Pacific islanders and has had centuries of use without major side effects. Standardised extracts of kava-kava produced in Europe have led to many serious health problems and even to death. The extraction process (aqueous vs. acetone in the two types of preparations) is responsible for the difference in toxicity as extraction of glutathione in addition to the kava lactones is important to provide protection against hepatotoxicity. The Michael reaction between glutathione and kava lactones, resulting in opening of the lactone ring, reduces the side effects of the kava kava extracts. This protective activity was demonstrated using Acanthamoebae castellanii in which 100% cell death occurred with 100 mg ml(-1) kava lactones alone, and 40% cell death with a mixture of 100 mg ml (-1)glutathione and 100 mg ml (-1) kava lactones. A comparison of kava lactone toxicity with other pharmaceutical products is discussed and recommendations made for safe usage of kava-kava products

This study presents results of field experiments conducted to identify factors determining kavalactone content and chemotype in Piper methysticum. The following factors have been studied: (1) the geographical direction of the roots on the plant, (2) the geographical location of the plant, (3) its age, and (4) its organ (roots, stumps, or basal stems). Overall, 185 samples were analysed by HPLC. It appears that the geographical direction of the roots (North, East, South, West) is not significant. Chemotype and kavalactone content variation among clones of a cultivar grown in a common garden is negligible. There is significant variation among different cultivars originating from the same island. The variation within island is comparable to the variation existing within the whole Vanuatu archipelago. For a given cultivar, chemotype is stable across locations. There are however, chemotype differences between organs. Kavalactone content is always higher in the roots than in the stumps and higher in the stumps than in the basal stems. Experimental data obtained from one cultivar indicate that at the juvenile stage (less than 18 months of growth), kavalactone content is still low but increasing progressively: from 3% of dry matter at 10 months to 8% at 17 months. After two years of vegetative growth, the chemotype appears stable and kavalactone content does not increase but rather fluctuates (±2%). Although seasonal factors might have an effect, it is not possible to observe a significant trend. It is confirmed that chemotype is genetically controlled. However, kavalactone content appears to be greatly determined by the growing conditions, either by the local environment or by the agricultural techniques used by the local farmers. Consequently, the selection of the cultivar, its organ and the geographical area of origin are factors contributing directly to quality control in Piper methysticum.

Standardized morphological descriptions, quantitative phytochemical analyses (HPLC) of major kavalactones and DNA fingerprinting (AFLP) were utilized to define the extent of variation existing between Hawaiian cultivars of Piper methysticum. For each cultivar, morphotypes and chemotypes were compared to their respective genotypes. Overall, 63 samples were analyzed for their kavalactone content and composition (44 root samples, 6 stump, 5 basal stem, 7 leaves and 1 peelings). Results obtained from different cultivars planted in an homogeneous environment (soil and climate) are quite variable for the kavalactone con-tent of their roots. Total kavalactone content decreases when shade increases over the plants. Total kavalactone content markedly increases with fertility, irrigation and in a cultivated type of habitat. However, kavalactone content appears to be independent of the age of the plant. For all cultivars analyzed, total kavalactone content decreases from the roots to the stump; the basal stems and the leaves exhibit the lower concentration. It is also observed that there is a correlation between the total kavalactone content and the size of the roots: smaller roots tend to have a higher kavalactone content. Peelings of the bark had a higher kavalactone content than the stump and represent a very interesting by-product for the extraction industry. Chemotypes are similar in the roots and the stump, while they differ in the aerial parts where the concentrations in dihydrokavain and dihydromethysticin increase. DNA samples were extracted from fresh leaves collected on 22 accessions. Most accessions, representing all Hawaiian morphotypes were monomorphs for the 21 pairs of primers assayed. Kava in Hawai'i is a species with an extremely narrow genetic base. Morphological and phytochemical variation is obviously controlled by very few genes. Most cultivars representing different morphotypes are most likely somatic mutants from a common clonal source introduced by Polynesians during early settlements.

A rapid micellar electrokinetic chromatography method with diode-array detection has been developed for the identification and quantitative determination of the therapeutically important styrylpyrones from Piper methysticum extracts and commercial drugs. Using fused-silica capillaries with a borate buffer containing sodium-taurodeoxycholic acid and β-cyclodextrin kavain, dihydrokavain, methysticin, dihydromethysticin, yangonin and demethoxyyangonin were fully separated and quantified within 15 min with 4-hydroxybenzoic acid methyl ester as I.S.

Kavalactone derivatives were synthesized using a Heck reaction of the 4-methoxy-6-vinyl-5,6-dihydropyran-2-one with aryl iodides. The Suzuki–Miyaura reaction of an aryl boronic acid and ( Z )-4-methoxy-6-(2-iodovinyl)-5,6-dihydropyran-2-one has also been successfully used to produce both Z and E isomers of lactones.

A reversed-phase high-performance liquid chromatographic method to simultaneously measure the six major kavalactones [methysticin, dihydromethysticin (DHM), kavain, dihydrokavain (DHK), demethoxyyangonin (DMY) and yangonin] in Piper methysticum (kava) has been successfully developed. The method uses the six compounds as external standards. These compounds were isolated in our laboratory using various chromatographic methods. The six compounds are completely separated within 35 min using a YMCbasic S-5 column and an isocratic methanol–acetonitrile–water–acetic acid (20:20:60:0.1, v/v) mobile phase at 40°C. The quantitative calibration curves are linear covering a range of 5–500 μg/ml for all six compounds. The detection limits ( S / N =3) for methysticin, DHM, kavain, DHK, DMY and yangonin are approximately 0.5, 1.1, 0.7, 1.1, 0.6 and 0.6 μg/ml, respectively. The average recoveries are 100.2% for methysticin, 100.6% for DHM, 100.0% for kavain, 100.3% for DHK, 98.9 for DMY and 98.2% for yangonin with R.S.D.s less than 3.6%. The six peaks in the HPLC chromatogram of kava extract were confirmed by LC–atmospheric pressure positive chemical ionization MS and their purities were examined by on-line UV and mass spectral analyses. In order to simplify the determination of the total kavalactone level, response factors and correlation factors relative to kavain were established.

La composition chimique de 121 cultivars de Piper mesthyticum originaires des 51 îles du Pacifique a été étudiée en utilisant la technique HLPC. Les résultats obtenus pour six kavalactones ont été soumis à une analyse de cluster et six types chimiques distincts ont été identifiés. Trois expérimentations au champ ont démontré que les types chimiques ne sont pas affectés par les facteurs environnementaux mais sont contrôlés génétiquement. L'analyse de la variation des isozymes pour huit systèmes enzymatiques a révélé que ces cultivars ne présentaient que trois zymotypes. Ils sont si semblables que les différences entre la malate deshydrogenase et la diaphorase pourraient être expliquées par des mutations. On pense que quelques gènes sont responsables de la variation des types chimiques entre des clones cultivés. Les cultivars sont décaploïdes et stériles. De ce fait, on a suggéré que la mutagenèse pourrait être utilisée pour provoquer une variabilité génétique et pour améliorer les types chimiques de cultivar

A new pyrone derivative, malakavalactone (2), was isolated from the acetone extract of Alpinia malaccensis fruits, along with a known compound kavalactone (1). The structure of the new compound was determined based on NMR and mass spectral data. Compounds 1 and 2 showed weak antibacterial activities against eight pathogenic bacteria.

Liver toxicity is a side effect observed with some herbal treatments, including Piper methysticum. The possible mechanisms responsible include inflammation subsequent to activation of liver macrophages and oxidative damage. Hepatotoxicity of the pharmacologically active component of Piper methysticum (kavalactones) was tested in isolated, perfused livers from rats which were pretreated with the macrophage intoxicant gadolinium chloride. Perfusions without kavalactones in gadolinium chloride pretreated and untreated livers were included as negative controls. Serial liver lobe biopsies were collected to measure temporal changes in available (reduced) hepatic glutathione. There were no statistically significant changes in reduced glutathione over the course of perfusion in any experimental group. Liver damage was observed using electron microscopy. Hepatic sinusoids displayed extensive damage to the endothelium in kavalactone-perfused, rat livers. This damage was significantly reduced by pre-treatment with gadolinium chloride. Hence liver macrophages may be a factor in liver injury induced by Piper methysticum. Characterisation and modulation of the liver macrophage response may enable the development of strategies to avoid these hepatic side effects.

Kava hepatotoxicity is a well described disease entity, yet there is uncertainty as to the culprit(s). In particular, there is so far no clear evidence for a causative role of kavalactones and non?kavalactone constituents, such as pipermethystine and flavokavain B, identified from kava. Therefore, novel enzymatic, analytical, toxicological, ethnobotanical and clinical studies are now required. Studies should focus on the identification of further potential hepatotoxic constituents, considering in particular possible adulterants and impurities with special reference to ochratoxin A and aflatoxins (AFs) producing Aspergillus varieties, which should be urgently assessed and published. At present, Aspergillus and other fungus species producing hepatotoxic mycotoxins have not yet been examined thoroughly as possible contaminants of some kava raw materials. Its occurence may be facilitated by high humidity, poor methods for drying procedures and insufficient storage facilities during the time after harvest. Various experimental studies are recommended using aqueous, acetonic and ethanolic kava extracts derived from different plant parts, such as peeled rhizomes and peeled roots including their peelings, and considering both noble and non?noble kava cultivars. In addition, ethnobotanical studies associated with local expertise and surveillance are required to achieve a good quality of kava as the raw material. In clinical trials of patients with anxiety disorders seeking herbal anxiolytic treatment with kava extracts, long?term safety and efficacy should be tested using traditional aqueous extracts obtained from peeled rhizomes and peeled roots of a noble kava cultivar, such as Borogu, to evaluate the risk: benefit ratio. Concomitantly, more research should be conducted on the bioavailability of kavalactones and non?kavalactones derived from aqueous kava extracts. To be on the side of caution and to ensure lack of liver injury, kava consuming inhabitants of the kava producing or importing South Pacific islands should undergo assessment of their liver function values and serum aflatoxin levels. The primary aim is to achieve a good quality of kava raw material, without the risk of adulterants and impurities including ochratoxin A and AFs, which represent the sum of aflatoxin B1, B2, G1 and G2. Although it is known that kava may naturally be contaminated with AFs, there is at present no evidence that kava hepatotoxicity might be due to aflatoxicosis. However, appropriate studies have yet to be done and should be extended to other mould hepatotoxins, with the aim of publishing the obtained results. It is hoped that with the proposed qualifying measures, the safety of individuals consuming kava will substantially be improved. (Resume d'auteur)

Overview: Kava ( Piper methysticum) is a South Pacific psychotropic plant medicine that has anxiolytic activity. This effect is achieved from modulation of GABA activity via alteration of lipid membrane structure and sodium channel function, monoamine oxidase B inhibition, and noradrenaline and dopamine re-uptake inhibition. Kava is available over the counter in jurisdictions such as the USA, Australia and New Zealand. Due to this, a review of efficacy, safety and clinical recommendations is advised. Objective: To conduct a comprehensive review of kava, in respect to efficacy, psychopharmacology, and safety, and to provide clinical recommendations for use in psychiatry to treat generalized anxiety disorder (GAD). Methods: A review was conducted using the electronic databases MEDLINE, CINAHL, PsycINFO and the Cochrane Library during mid 2010 of search terms relating to kava and GAD. A subsequent forward search was conducted of key papers using Web of Science cited reference search. Results: The current weight of evidence supports the use of kava in treatment of anxiety with a significant result occurring in four out of six studies reviewed (mean Cohen's d = 1.1). Safety issues should however be considered. Use of traditional water soluble extracts of the rhizome (root) of appropriate kava cultivars is advised, in addition to avoidance of use with alcohol and caution with other psychotropic medications. Avoidance of high doses if driving or operating heavy machinery should be mandatory. For regular users routine liver function tests are advised. Conclusions: While current evidence supports kava for generalized anxiety, more studies are required to assess comparative efficacy and safety (on the liver, cognition, driving, and sexual effects) versus established pharmaceutical comparators.

While cases of severe kava hepatotoxicity have been reported, studies examining the toxicity of individual kavalactones are limited. The present study examined the in vitro hepatotoxicity of kavain, methysticin and yangonin on human hepatocytes (HepG2) and the possible mechanism(s) involved. Cytotoxicity was assessed using lactate dehydrogenase (LDH) and ethidium bromide (EB) assays. The mode of cell death was analysed with acridine orange/ethidium bromide dual staining with fluorescence microscopy. Glutathione oxidation was measured using the ortho-phthalaldehyde (OPT) fluorescence assay. Kavain had minimal cytotoxicity, methysticin showed moderate concentration-dependent toxicity and yangonin displayed marked toxicity with ∼40% reduction in viability in the EB assay. Acridine orange/ethidium bromide staining showed the predominant mode of cell death was apoptosis rather than necrosis. No significant changes were observed in glutathione levels, excluding this as the primary mechanism of cell death in this model. Further studies may elucidate the precise apoptotic pathways responsible and whether toxic kavalactone metabolites are involved. Copyright © 2010 John Wiley & Sons, Ltd.