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Context Stomach ulcer is one of the most common gastrointestinal problems in the world. Objective This study aimed to isolate flavonoid compounds from methanol extract of the aerial parts of Stachytarpheta jamaicensis (L.) Vahl. and evaluate its protective and therapeutic effects against gastric ulcer. Materials and methods Chromatographic techniques were used for the identification of the isolated compounds. To explore the effects of the plant extract, it was administrated by oral gavage for one week either before or post-ethanol ulcer induction. Ranitidine was also evaluated as a reference drug. Stomach pH, gastric juice volume, lesions number, glutathione, superoxide dismutase, malondialdehyde, succinate dehydrogenase, lactate dehydrogenase, acid phosphatase, Interleukin-10, intracellular adhesion molecule-1, prostaglandin E2, and total protein levels were estimated in gastric tissue. Stomach histopathological features were also monitored. Results Six flavonoid compounds were isolated, where five of them were isolated for the first time (vitexin, isovitexin, apigenin 7,4'-dimethyl ether, 5,7,2'-trimethoxyflavone, and scutellarein), while apigenin was previously reported. Treatment with plant extract recorded amelioration in all the biochemical parameters. Conclusion The methanol extract of plant aerial parts had prophylactic and treatment effects against gastric ulcer in rats, where its treatment effect exceeded its protective role. The extract recorded anti-inflammatory, and antioxidant effects due to the presence of flavonoid compounds.

Baicalein and scutellarein are bioactive flavonoids isolated from the traditional Chinese medicine Scutellaria baicalensis Georgi; however, there is a lack of effective strategies for producing baicalein and scutellarein. In this study, we developed a sequential self-assembly enzyme reactor involving two enzymes in the baicalein pathway with a pair of protein-peptide interactions in E. coli. These domains enabled us to optimize the stoichiometry of two baicalein biosynthetic enzymes recruited to be an enzymes complex. This strategy reduces the accumulation of intermediates and removes the pathway bottleneck. With this strategy, we successfully promoted the titer of baicalein by 6.6-fold (from 21.6 to 143.5 mg/L) and that of scutellarein by 1.4-fold (from 84.3 to 120.4 mg/L) in a flask fermentation, respectively. Furthermore, we first achieved the de novo biosynthesis of baicalein directly from glucose, and the strain was capable of producing 214.1 mg/L baicalein by fed-batch fermentation. This work provides novel insights for future optimization and large-scale fermentation of baicalein and scutellarein.

Although the in vivo metabolic pathways of scutellarin, a traditional Chinese medicine, have been investigated via different liquid chromatography techniques, studies on the distribution and location of scutellarin within organ tissue sections have not been reported. Matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) can generate in situ spatial distribution profiles for scutellarin and its metabolites in a kidney section. However, the direct detection of a small molecule (m/z < 600) using conventional matrices often results in ion suppression and matrix interferences. In this study, we demonstrated a novel methodology using MALDI-MSI for the in situ spatial localization of scutellarin and its metabolites in kidney tissues by applying a binary matrix of graphene oxide (GO) and caffeic acid (CA). The results indicated that the binary matrix (GO/CA) significantly improved the detection efficiency of scutellarin and its metabolites with relatively high sensitivity, selectivity and reproducibility on tissue sections. This methodology was successfully applied to map scutellarin and its metabolites with MALDI-MSI in mouse kidney tissues. Specifically, scutellarin and scutellarein were found to be located in the cortex and medulla regions of the kidney with relatively high abundance, whereas the remaining metabolites appeared in the cortex with low abundance. We believe that the novel imaging methodology may also be used for the studies of cancerous tissues and inform the development of the future therapies of kidney tumors.

Scutellaria baicalensis and Scutellaria barbata, common medicinal plants of the Lamiaceae family, produce specific flavonoid compounds with antioxidant and antitumor activities, including baicalein, scutellarein, norwogonin, wogonin, and their glycosides. Here, we reported two chromosome-level genome assemblies of S. baicalensis and S. barbata with significant quantitative chromosomal variation (2n = 18 and 2n = 26, respectively). The divergence of S. baicalensis and S. barbata occurred far earlier than previously reported, and a whole-genome duplication event was identified. The insertion of long terminal repeat elements after speciation might be responsible for the observed chromosomal expansion and rearrangement. The comparative genome analysis of congeneric species elucidated the species-specific evolution of chrysin and apigenin biosynthetic genes, such as the S. baicalensis-specific tandem duplication of the phenylalanine ammonia lyase (PAL) and chalcone synthase (CHS) genes, and the S. barbata-specific duplication of 4-CoA ligase (4CL) genes. In addition, the paralogous duplication, collinearity, and expression diversity of CYP82D subfamily members revealed the functional divergence of flavone hydroxylase genes between S. baicalensis and S. barbata. These Scutellaria genomes highlight the common and species-specific evolution of flavone biosynthetic genes, promoting the development of molecular breeding and the study of the biosynthesis and regulation of bioactive compounds.

The hydroethanolic extract obtained from the dry leaves of Fridericia chica (HEFc) underwent several fractionations by different chromatographic techniques. The ethyl acetate and dichloromethane fraction were subjected to phytochemical analysis, resulting in the identification and isolation of scutellarein (1) and in a fraction rich in carajurone (2). They were tested for cytotoxicity in CHO-K1 and the antibacterial activity and mode of action by in vitro assays. The HEFc and scutellarein (1) presented no cytotoxicity. The results showed good antibacterial effect of HEFc against Streptococcus pyogenes and Staphylococcus aureus and moderate activity for Staphylococcus epidermidis, Pseudomonas aeruginosa and Salmonella typhimurium. The fraction containing the compound carajurone (2) showed good activity against Staphylococcus aureus and Staphylococcus epidermidis and moderate activity against Streptococcus pyogenes. Scutellarein (1) showed no activity against the bacteria tested. HEFc antibacterial mode of action appeared to be associated with changes in the permeability of bacterial membranes and nucleotide leakage.

Background: Exogenous antioxidants are considered as a promising therapeutic approach to treat neurodegenerative diseases since they could prevent and/or minimize the neuronal damage by oxidation. Objective: Three series of lipophilic compounds structurally based on scutellarein (2), which is one metabolite of scutellarin (1) in vivo, have been designed and synthesized. Methods: Their antioxidant activity was evaluated by detecting the 2-thiobarbituric acid reactive substance (TBARS) produced in the ferrous salt/ascorbate-induced autoxidation of lipids, which were present in microsomal membranes of rat hepatocytes. The lipophilicity of these compounds indicated as partition coefficient between n-octanol and buffer was investigated by ultraviolet (UV) spectrophotometer. Results: This study indicated that compound 5e which had a benzyl group substituted at the C4'- OH position showed a potent antioxidant activity and good lipophilicity. Conclusion: 5e could be an effective candidate for preventing or reducing the oxidative status associated with the neurodegenerative processes.

Two new flavonoid glycosides, named oroxin C (1) and oroxin D (scutellarein 4'-methyl ether 7-O-β-D-glucopyranosyl-(1→6)-β-D-glucopyranoside, 2), together with eight known flavonoids (3–10), were isolated from the seeds of Oroxylum indicum. Their structures were elucidated unambiguously by spectroscopic techniques and chemical methods. Anti-inflammatory and cytotoxic activities of all the isolated compounds were evaluated. Chrysin (3) and chrysin-6-C-β-D-glucopyranosyl-8-C-α-L-arabinopyranoside (10) showed moderate inhibitory effects aganist the LPS-induced NO production in murine RAW264.7 macrophages with IC50 values of 18.63 ± 0.91 and 28.69 ± 0.43 μM, respectively. Chrysin (3) exhibited weak cytotoxic activity aganist A549, HepG2 and SW480 human cancer cell lines with IC50 values of 40.88 ± 3.85, 50.55 ± 2.59 and 91.60 ± 4.27 μM, respectively.

The polyphenolic composition and anti-inflammatory activity of selected Thymus species (T. longicaulis C. Presl, T. praecox Opiz subsp. polytrichus (A. Kerner Ex Borbas) Jalas, T. pulegioides L., T. serpyllum L. subsp. serpyllum and T. striatus Vahl) was studied in comparison with T. vulgaris, as an officinal medicinal plant, to evaluate the biomedical potential of these Croatian wild-growing species. This paper provides a first insight into the polyphenolic profiles of T. praecox subsp. polytrichus and T. striatus. Also, some flavone and hydroxycinnamic derivatives were at first identified in the other studied species by LC-DAD-ESI–MS/MS analysis. Rosmarinic acid and glycosides of scutellarein and luteolin were found to be the most abundant polyphenolic constituents. The Thymus extracts inhibited Src tyrosine kinase activity and they reduced the production of proinflammatory cytokine interleukin-6 in Balb/C mice splenocytes. The obtained results highlighted T. longicaulis as a potential source of herbal drugs with anti-inflammatory properties and/or novel functional food rich in flavonoids and phenolic acids.

Scutellarein, a flavone found in the perennial herb Scutellaria baicalensis, has antitumorigenic activity in multiple human cancers. However, whether scutellarein can attenuate ovarian cancer (OC) is unclear. This study investigated the effects of scutellarein in OC. In vitro cell viability was assessed using MTT assay whereas proliferation was assessed using 5-ethynyl-2'-deoxyuridine and colony formation assays. Cell apoptosis was detected by an Annexin V-fluorescein isothiocyanate/propidium iodide assay. Wound-healing and Transwell assays were used to determine cell migration and invasion. The differential expression of enhancer of zeste homolog 2 (EZH2) and forkhead box protein O1 (FOXO1) was measured by Quantitative real-time PCR and western blot analysis. We found that scutellarein inhibited viability, migration, invasion of A2780 and SKOV-3 cells, and reduced the expression of EZH2 in OC cells. In addition, FOXO1 was downregulated in OC tissues and cells and negatively regulated by EZH2. Also, scutellarein inhibited tumor growth and metastasis in vivo. In conclusion, scutellarein alleviates OC by the regulation of EZH2/FOXO1 signaling.

Flavonoids are potential nutraceutical compounds present in diary food. They are considered health-promoting compounds and promising drugs for different diseases, such as neurological and inflammatory diseases, diabetes and cancer. Therefore, toxicological and mechanistic studies should be done to assert the biological effects and identify the molecular targets of these compounds. In this work we describe the effects of six structurally-related flavonoids—baicalein, chrysin, scutellarein, 6-hydroxyflavone, 6,7-dihydroxyflavone and 7,8-dihydroxyflavone—on Caenorhabditis elegans’ lifespan and stress resistance. The results showed that chrysin, 6-hydroxyflavone and baicalein prolonged C. elegans’ lifespan by up to 8.5%, 11.8% and 18.6%, respectively. The lifespan extensions caused by these flavonoids are dependent on different signaling pathways. The results suggested that chrysin’s effects are dependent on the insulin signaling pathway via DAF-16/FOXO. Baicalein and 6-hydroxyflavone’s effects are dependent on the SKN-1/Nfr2 pathway. In addition, microarray analysis showed that baicalein downregulates important age-related genes, such as mTOR and PARP.

Introduction With the wide application of Scutellaria barbata D. Don for hepatitis and mastitis, its quality control issues have also received increasing attention. Based on the multi-component and multi-target characteristics of traditional Chinese medicine, there is an urgent need to establish a quality evaluation system. Objectives This study intends to integrate the "quality-activity-quantification" strategy and establish an activity-related quality control method to ensure the safety and effectiveness of S. barbata. Material and methods Ultra-high performance liquid chromatography/ion mobility-quadrupole time-of-flight mass spectrometry (UPLC/IM-QTOF-MS) was used to characterize the chemical components of S. barbata, and network pharmacological analysis was carried out on the identified components. The index components were determined on the basis of comprehensive activity prediction results and content information. At the same time, the contents of 16 batches of S. barbata from different origins were determined. Results A total of 94 compounds were identified according to mass spectrometric data, 12 of which were isolated and structure-confirmed by nuclear magnetic resonance technology. Network pharmacological analysis was applied to predict their key targets and the major pathways mediating their anti-inflammatory effects. On the basis of comprehensive activity prediction and content information, five components were chosen as crucial quality indicators of S. barbata, including scutellarin, scutellarein, luteolin, apigenin, and hispidulin. Conclusion In this study, 16 different S. barbata batches were compared, and five quality indicators were determined on the basis of qualitative and activity results. The present study provides useful information for evaluating the quality of S. barbata in different areas, and also provides a new basis for the development of quality evaluation methods.

Polar auxin transport (PAT) is essential to control root growth. Flavonoids are widely thought to be PAT inhibitors leading to short root developments. However, we found that the flavonoids scutellarin and scutellarein, which both have a 6-hydroxyl group unlike the structure of known flavonoid-PAT-inhibitors, promote PAT in roots. They increase root length; rescue the short roots induced by the PAT-specific inhibitor TIBA; enhance the expression of the PAT mediators PIN1, PIN2 and AUX1; increase the auxin concentration at the quiescent center; and change the distribution of the meristem organizer WOX5. In contrast, rutin and naringenin, which have no 6-hydroxyl group and have different structural features in B-ring, shows the opposite/no effects. Our evidence suggests that flavonoids with and without a 6-hydroxyl group might result in opposite effects on root growth and thus act as chemical switches in regulating PAT.

Scutellaria araxensis, S. bornmuelleri and S. orientalis are traditional herbs widely used by native Iranians for the treatment various ailments. In the current study, we used HPLC-DAD-ESI/MSn to investigate the presence of phenolic compounds of root and shoot methanolic extracts. The flavonoid composition were identified based on mass of pseudomolecular [M − H]− ions and fragmentation spectra and comparisons with literature data. A total of 26, 25, 17, 23, 19 and 26 flavonoids were identified from roots and shoots of S. araxensis, S. bornmuelleri and S. orientalis, respectively. The obtained phenolic profiles revealed the presence of the major flavonoid components of Scutellaria genus including baicalein, wogonin, scutellarein and their glycosides, as well as chrysin, tricin, skullcapflavon II, pinocembrin and phenylethanoid glycosides such as acteoside and verbascoside. This study, in addition to reveal the potency of chromatographic profiling for identification of Scutellaria flavonoids, introduces this species as a potential source of bioactive metabolites.

To search novel therapy for human colon cancer, scutellarein identified from Scutellaria barbata was investigated using HCT116 cells. As a result, scutellarein can induce apoptosis of HCT116 cells. Further investigation for the mechanism has revealed scutellarein can increase the production of intracellular ROS and lead to the collapse of mitochondrial membrane potential. Meanwhile, the activity of caspase-3 in HCT116 cells was elevated by scutellarein. Moreover, down-regulated Bcl-2 and up-regulated Bax were observed. Additionaly, scutellarein resulted in cytochrome c release from mitochondria. These results indicated the apoptosis induction of HCT116 cells by scutellarein was implemented through ROS-mediated mitochondria-dependent pathway.

Hit, Lead & Candidate Discovery Glyoxalase-I (Glo-I) enzyme has emerged as a potential target for cancer treatment. Several classes of natural products including coumarins and flavonoids have shown remarkable Glo-I inhibitory activity. In the present study, computational and experimental approaches were used to explore the structure-activity relationships of a panel of 24 flavonoids as inhibitors of the Glo-1 enzyme. Scutellarein with an IC50 value of 2.04 μM was identified as the most potent inhibitor among the series studied. Di- or tri-hydroxylation of the benzene rings A and B accompanied with a C2/C3 double bond in ring C were identified as essential structural features for enzyme inhibition. Moreover, the ketol system showed a minor role in the inhibitory power of these compounds. The structure-activity relationships revealed in this study had deepened our understanding of the Glo-I inhibitory activities of flavonoids and opened the door for further exploration of this promising compound class.

Flavonoid compounds have anti-diabetic activity, which can control blood glucose levels by inhibiting α-glucosidase activity. In this paper, the inhibition mechanisms between four flavonoid compounds and α-glucosidase were studied by multispectroscopic methods and molecular docking. The results showed that the inhibitory activities of flavonoid compounds were higher than that of acarbose, and the sequence of inhibition effect was scutellarein > nepetin > apigenin > hispidulin > acarbose. Also, the synergistic effects of flavonoid compounds combined with acarbose on inhibiting α-glucosidase activity were observed. The fluorescence results showed that flavonoid compounds combined with α-glucosidase to form a stable complex. And the spectral analysis indicated that the microenvironmental and secondary structure of α-glucosidase were changed. The present study demonstrated that the molecular structure of flavonoid compounds played an important role in the inhibition process, namely, scutellarein with more hydroxyl groups on the A-ring might serve as the most effective α-glucosidase inhibitor.

Hyperuricemia is a clinical condition characterized by an elevated level of serum uric acid and is a key risk factor for the development of gout and metabolic disorders. The existing urate-lowering therapies are often impractical for certain patient populations, providing a rationale to explore new agents with improved safety and efficacy. Here, we discovered that Salvia plebeia extract inhibited the enzyme activity of xanthine oxidase, which is a key enzyme generating uric acid in the liver. In an animal model of hyperuricemia, S. plebeia extract reduced serum urate to the levels observed in control animals. The urate-lowering effect of S. plebeia extract in vivo was supported by the identification of compounds that inhibit xanthine oxidase enzyme activity in vitro. Nepetin, scutellarein, and luteolin contributed significantly to S. plebeia bioactivity in vitro. These compounds showed the highest potency against xanthine oxidase with IC50 values of 2.35, 1.74, and 1.90 µM, respectively, and were present at moderate quantities. These observations serve as a basis for further elaboration of the S. plebeia extracts for the development of new therapeutics for hyperuricemia and related diseases.

A rapid, sensitive and specific ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method was developed and validated to simultaneously determine the twelve major bioactive ingredients (neochlorogenic acid, chlorogenic acid, caffeic acid, cynarin, scopoletin, scutellarin, isochlorogenic acid A, apigenin-7-o-glucuronide, isochlorogenic acid C, scutellarein, luteolin, and apigenin) in rat plasma. Gallic acid and wogonoside were used as internal standards (IS1 and IS2). The plasma samples were pretreated and extracted by liquid-liquid extraction and protein precipitation with ethyl acetate-acetonitrile (95:5, v/v). Chromatographic separation was accomplished on Agilent ZORBAX RRHD Eclipse Plus C18 column (2.1mm×50mm, 1.8μm) utilizing 0.1% formic acid aqueous solution and acetonitrile as mobile phase under gradient conditions at a flow rate of 0.3mL·min-1. Mass spectrometric detection was performed in multiple reaction monitoring (MRM) mode using electrospray ionization (ESI) in positive and negative mode. The whole intra- and inter-day precision (as relative standard deviation) of all analytes were less than 11.03%, and the accuracy (as relative error) were in the range from -10.43% to 9.76% and from -10.14% to 10.33%. The lower limits of quantification (LLOQ) were 20, 3.0, 100, 7.0, 0.30, 2.0, 70, 1.0, 20, 30, 10, and 2.0ngmL-1 for neochlorogenic acid, chlorogenic acid, caffeic acid, cynarin, scopoletin, scutellarin, isochlorogenic acid A, apigenin-7-o-glucuronide, isochlorogenic acid C, scutellarein, luteolin, and apigenin, respectively. Extraction recovery, matrix effect and stability were found to be the required limits. This method was selective and sensitive for the investigation of the pharmacokinetics of twelve constituents following oral administration to research study about in Erigeron breviscapus of clinical practices for separately analytes on rats.

Ingredients in traditional Chinese medicine (TCM) can be absorbed into blood and reach and maintain effective concentrations in the target organ, which is the premise of the ingredients taking effect in vivo. Hollow fibre cell fishing (HFCF) based on ACHN human renal tubular cells or HepG2 hepatoma cells using high-performance liquid chromatography with ultraviolet detection (HPLC/UV), coupled with hollow fibre liquid-phase microextraction (HF-LPME) with HPLC/UV, was developed and employed for the first time to study the antitumour activity of scutellarin, a main ingredient in breviscapine, and its metabolite scutellarein after intraperitoneal injection of breviscapine. The antitumour activity of these ingredients was evaluated by combining their activity screening, target tissue distribution and pharmacokinetics (PK). Before application, the cell growth state, survival rate, binding between fibre active centre or nutrient solution and ingredients, positive and negative control and repeatability for HFCF were investigated; validations of the HF-LPME methodology were optimized and evaluated. The study found that scutellarin can be rapidly absorbed into blood and metabolize partly into scutellarein, and both can reach liver or kidney, combine with ACHN or HepG2 cells and maintain effective concentrations. Thus, scutellarin and scutellarein have potential as lead ingredients for treatment of liver or kidney tumours, and breviscapine injection may have potential properties for use in treatment or prevention of liver and kidney tumours, at least. HFCF and HF-LPME coupled with HPLC can contribute to simultaneous investigation of the antitumour activity of multiple ingredients in TCMs by combining activity screening, tissue distribution and PK studies.

Neoplastic cells often reside in distinctive tumor hypoxia armed with a series of adaptive responses including oxidative stress, defective apoptotic machinery and neoangiogenesis, through that further confer cell survival improvement. Plants still acts as reservoir of natural chemicals to provide newer active pharmacophores. Scutellarein is flavones which has wide range of pharmacophoral effects. In our current research, scutellarein employed for targeting oxidative stress mediated tumor angiogenesis and apoptotic nuclear fragmentation. Experimental results revealed that scutellarein has antiproliferative index against multiple cancer cell lines and diminished the oxidative stress and tumor development of murine ascitic lymphoma & inflammatory hepatocellular carcinoma. Eventual consequences lead to reduced neovessel formation by abrogating angiogeneic factors cytokine-VEGF-A, Flt-1, HIF-1α, MMP-2 and MMP-9 and reversing of evading apoptosis by activating caspase-3 activated DNA fragmentation factor (DFF-40) mediated nucleosomal degradation. In summary, our experimental evidences suggest that scutellarein has strong potentiality to attenuate the tumor development by modulating sprouting neovasculature and DFF-40 mediated apoptosis.

A series of hybrid molecules of scutellarein and tertramethylpyrazine's active metabolites have been synthesized. Compared to the original compound, these prepared compounds exhibited higher water solubility, more appropriate logP and better stability. Importantly, compounds 11b, 11d and 11e showed improved neuroprotective activity against the H2O2-induced cell death in PC12 cells, and better antithrombosis activity. The optimized compound 11b was further evaluated by cerebral ischemia/ reperfusion in the middle cerebral artery occlusion (MCAO) model, the results showed that the compound could significantly reduce the infarct area and decrease the neuronal cell damage in CA1 pyramidal neurons. Overall, we demonstrated that the twin drug strategy could be applied in the development of agents for the treatment of ischemic stroke.

Patrinia villosa (Thunb.) Juss. (PVJ) is described as pungent, bitter and slightly cold in Chinese medicine, and is associated with the large intestine, stomach and liver meridians. The preliminary experiments of our research team proved that PVJ total flavonoids have excellent inhibitory effects on liver cancer cells. The present experiment uses the UPLC-Q-TOF-MS technology and serum pharmacochemistry methods to analyze the chemical components in vitro and in vivo of PVJ antiliver tumors. A total of 14 chemical components were identified in the total flavonoids extract of PVJ, and it is mainly composed of flavonoids, flavonones, flavonols and phenolic acids. At the same time, seven prototypical components and seven metabolic components were detected in the drug-containing plasma. Hydrocaffeate and scutellarein are the phase I metabolites of caffeic acid and scutellarin, respectively. Sulfated apigenin, sulfated luteolin, sulfated kaempferol and methylated kaempferol are the II phase metabolites of apigenin, luteolin, kaempferol, respectively. The experiment provides a reference for the research and development of antitumor drug candidates, and provides a basis for revealing the bioactive components of PVJ and the antitumor mechanism.

Background Hispidulin (Scutellarein 6-methyl ether or dinatin, HPD) is a flavone derivative found in plant exhibiting anti-oxidant, anti-inflammatory, anti-mutagenic, and anti-epileptic properties....

A general protocol for direct glucuronic linkages formation featuring Au(I)-catalyzed appropriately protected glucuronyl o-alkynylbenzoate-involved glycosylation reaction, as well as a concise approach for easy access of scutellarein prominent for the mild and efficient hydroxyl group installation via borylation-oxidation sequence from flavanone derivative, has been established, based on which a novel route for scutellarin derivatives preparation has been devised. The developed strategies, among which the stepwise deprotection process was also included, guarantee the high whole synthetic efficiency, and definitely will find broad application in diversity-oriented synthesis of bioactive flavonoid glycosides.

Baicalein and scutellarein are bioactive flavones found in the medicinal plant Scutellaria baicalensis Georgi, used in traditional Chinese medicine. Extensive previous work has demonstrated the broad biological activity of these flavonoids, such as antifibrotic, antiviral and anticancer properties. However, their supply from plant material is insufficient to meet demand. Here, to provide an alternative production source and increase production levels of these flavones, we engineered an artificial pathway in an Escherichia coli cell factory for the first time. By first reconstructing the plant flavonoid biosynthetic pathway genes from five different species: phenylalanine ammonia lyase from Rhodotorula toruloides (PAL), 4-coumarate-coenzyme A ligase from Petroselinum crispum (4CL), chalcone synthase from Petunia hybrida (CHS), chalcone isomerase from Medicago sativa (CHI) and an oxidoreductase flavone synthase I from P. crispum (FNSI), production of the intermediates chrysin and apigenin was achieved by feeding phenylalanine and tyrosine as precursors. By comparative analysis of various versions of P450s, a construction expressing 2B1 incorporated with a 22-aa N-terminal truncated flavone C-6 hydroxylase from S. baicalensis (F6H) and partner P450 reductase from Arabidopsis thaliana (AtCPR) was found most effective for production of both baicalein (8.5 mg/L) and scutellarein (47.1 mg/L) upon supplementation with 0.5 g/L phenylalanine and tyrosine in 48 h of fermentation. Finally, optimization of malonyl-CoA availability further increased the production of baicalein to 23.6 mg/L and scutellarein to 106.5 mg/L in a flask culture. This report presents a significant advancement of flavone synthetic production and provides foundation for production of other flavones in microbial hosts.

To discover multifunctional agents for the treatment of Alzheimer's disease (AD), a series of scutellarein carbamate derivatives were designed and synthesized based on the multitarget-directed ligand strategy. Their acetylcholinesterase and butyrylcholinesterase inhibitory activities, antioxidant activities, metal-chelating properties and neuroprotective effects against hydrogen peroxide induced PC12 cell injury were evaluated in vitro. The results showed that most of the synthetic compounds exhibited good multifunctional activities. In particular, compound 15c exhibited dual inhibitory potency on acetylcholinesterase and butyrylcholinesterase with IC50 values of 0.57 and 22.6μM, respectively, and good antioxidative activity, with a value 1.3-fold of Trolox. In addition, 15c acted as a selective biometal chelator and possessed neuroprotective effects. Furthermore, 15c could cross the blood-brain barrier (BBB) in vitro and had significant neuroprotective effects in scopolamine-induced cognitive impairment in mice. Taken together, these results suggest that compound 15c might be a potential multifunctional agent for the treatment of AD.

Radix Scutellariae (RS) is a herbal medicine with various pharmacological activities to treat inflammation, respiratory and gastrointestinal infections, etc. In this study, a rapid, sensitive and selective UPLC-ESI-MS/MS method was developed for simultaneous determination of 10 flavonoids - scutellarin, scutellarein, chrysin, wogonin, baicalein, apigenin, wogonoside, oroxylin A-7-O-glucuronide, oroxylin A and baicalin - from RS aqueous extracts in rat plasma with propyl paraben as internal standard (IS). Chromatographic separation was achieved on a C18 column using gradient elution with the mobile phase consisting of methanol and water (containing 0.1% formic acid) at a flow rate of 0.2 mL/min. The detection was performed in multiple reaction monitoring mode using electrospray ionization in negative mode. The validated method showed good linearity over a wide concentration range (r >0.9935). The intra- and interday assay variabilities were

Scutellaria lateriflora (American skullcap) has been used in traditional medicine to treat several medical conditions including nervous disorders and cancer. Previous studies have associated these medicinal properties to flavones present in roots and leaves of this species. In order to develop a production system and study the biosynthesis of these bioactive compounds, hairy root cultures of S. lateriflora were established and line 4 was selected for further studies based on its growth performance in a modified Murashige and Skoog’s medium supplemented with 0.5 mg/l indole-3-butyric acid. Scanning electron microscopy of the hairy roots showed a high profusion of hairs along the root. Several phenolic compounds, including verbascoside, and the flavones wogonin, baicalein, scutellarein and their respective glucuronides were identified by high performance liquid chromatography–tandem mass spectrometry in the root tissue, but not in the culture medium. Among these compounds, verbascoside accumulated at the highest levels. Interestingly, cultures incubated under continuous light and treated with 15 mM methyl-β-cyclodextrin for 24 h produced significantly higher levels of the aglycones, baicalein and wogonin, but not scutellarein, compared to cultures incubated under continuous darkness. This work demonstrates that hairy root cultures of S. lateriflora have the biosynthetic capacity to produce known Scutellaria flavones and suggest that light may have a selected regulatory effect on the synthesis or accumulation of these phenolic compounds.

The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link. Natural flavonoids with methoxy substitutions are metabolized by CYP1 enzymes to yield the corresponding demethylated products. The present study aimed to characterize the metabolism and further antiproliferative activity of the hydroxylated flavonoids apigenin, luteolin, scutellarein, kaempferol and quercetin in CYP1 recombinant enzymes and in the CYP1 expressing cell lines MCF7 and MDA–MB–468, respectively. Apigenin was converted to luteolin and scutellarein, whereas kaempferol was metabolized only to quercetin by recombinant CYP1 enzymes. Luteolin metabolism yielded 6 hydroxyluteolin only by recombinant CYP1B1, whereas CYP1A1 and CYP1A2 were not capable of metabolizing this compound. Molecular modeling demonstrated that CYP1B1 favored the A ring orientation of apigenin and luteolin to the heme group compared with CYP1A1. The IC50 of the compounds luteolin, scutellarein and 6 hydroxyluteolin was significantly lower in MDA–MB–468, MCF7 and MCF10A cells compared with that of apigenin. Similarly, the IC50 of quercetin in MDA–MB–468 cells was significantly lower compared with that of kaempferol. The most potent compound was luteolin in MDA–MB–468 cells (IC50= 2±0.3 μM). In the presence of the CYP1-inhibitors α-napthoflavone and/or acacetin, luteolin activation was lessened. Taken collectively, the data demonstrate that the metabolism of hydroxylated flavonoids by cytochrome P450 CYP1 enzymes, notably CYP1A1 and CYP1B1, can enhance their antiproliferative activity in breast cancer cells. In addition, this antiproliferative activity is attributed to the combined action of the parent compound and the corresponding CYP1 metabolites.

Scutellarin, one of natural flavonoids, is widely and clinically used for treating many diseases in China. Recently, scutellarin has demonstrated a broad spectrum of anti-proliferative activities against multiple cancer cell lines. However, the molecular mechanism of action remains to be investigated. We herein report the design and synthesis of biotinylated scutellareins as probes, which can be applied to discover scutellarein interacting proteins. Finally, we show that scutellarin directly targets pyruvate kinase M2 (PKM2) and inhibits its cytosolic activity to decrease glycolytic metabolism; on the other hand, scutellarin may also participate in regulating cell cycle and apoptotic proteins by activating MEK/ERK/PIN1 signaling pathway to promote the nuclear translocation of PKM2.

Baicalein, wogonin, and their glycosides are major bioactive compounds found in the medicinal plant Scutellaria baicalensis Georgi. These flavones can induce apoptosis in a variety of cancer cell lines but have no effect on normal cells. Furthermore, they have many additional benefits for human health, such as anti-oxidant, antiviral, and liver-protective properties. Here, we report the isolation and characterization of two CYP450 enzymes, SbCYP82D1.1 and SbCYP82D2, which function as the flavone 6-hydroxylase (F6H) and flavone 8-hydroxylase (F8H), respectively, in S. baicalensis. SbCYP82D1.1 has broad substrate specificity for flavones such as chrysin and apigenin and is responsible for biosynthesis of baicalein and scutellarein in roots and aerial parts of S. baicalensis, respectively. When the expression of SbCYP82D1.1 is knocked down, baicalin and baicalein levels are reduced significantly while chrysin glycosides accumulate in hairy roots. SbCYP82D2 is an F8H with high substrate specificity, accepting only chrysin as its substrate to produce norwogonin, although minor 6-hydroxylation activity can also be detected. Phylogenetic analysis suggested that SbCYP82D2 might have evolved from SbCYP82D1.1 via gene duplication followed by neofunctionalization, whereby the ancestral F6H activity is partially retained in the derived SbCYP82D2., We report the characterization of two CYP450 enzymes, which 6- and 8-hydroxylate chrysin to form the 4′-deoxyflavone bioactives in roots of Scutellaria baicalensis. Like the main 4′-deoxyflavone enzymes, these decorating enzymes have evolved their functionalities by convergence with the more ubiquitous 4′-hydroxyflavone pathway enzymes.

Apigenin, a widely distributed flavone, exhibits excellent antioxidant, anti-inflammatory, and antitumor properties. In addition, the methylation of apigenin is generally considered to result in better absorption and greatly increased bioavailability. Here, four putative Class II methyltransferase genes were identified from the transcriptome sequences generated from the liverwort species Plagiochasma appendiculatum. Each was heterologously expressed as a His-fusion protein in Escherichia coli and their methylation activity against apigenin was tested. One of the four Class II OMT enzymes named 4′-O-methyltransferase (Pa4′OMT) was shown to react effectively with apigenin, catalyzing its conversion to acacetin. Besides the favorite substrate apigenin, the recombinant PaF4′OMT was shown to catalyze luteolin, naringenin, kaempferol, quercetin, genistein, scutellarein, and genkwanin to the corresponding 4′-methylation products. In vivo feeding experiments indicated that PaF4′OMT could convert apigenin to acacetin efficiently in E. coli and approximately 88.8 µM (25.2 mg/L) of product was synthesized when 100 µM of apigenin was supplemented. This is the first time that a Class II plant O-methyltransferase has been characterized in liverworts.

Bacterial β-glucuronidases play key roles in the deconjugation of a variety of endogenous and drug glucuronides, thus have been recognized as important targets to modulate the enterohepatic circulation of various glucuronides. In this study, more than 30 natural flavonoids were collected and their inhibitory effects against E. coli β-glucuronidase (EcGUS) were assayed. The results demonstrated that some flavonoids including scutellarein, luteolin, baicalein, quercetin and scutellarin displayed strong to moderate inhibitory effects against EcGUS, with the IC50 values ranging from 5.76 μM to 29.64 μM, while isoflavones and dihydroflavones displayed weak inhibitory effects against EcGUS. Further investigation on inhibition kinetics revealed that scutellarein and luteolin functioned as potent competitive inhibitors against EcGUS-mediated PNPG hydrolysis, with the Ki values less than 3.0 μM. Molecular docking simulations demonstrated that scutellarein and luteolin could be well-docked into the catalytic site of EcGUS, while the binding areas of these two natural inhibitors on EcGUS were highly overlapped with that of PNPG on EcGUS. Additionally, the structure-inhibition relationships of natural flavonoids against EcGUS are also summarized, which will be very helpful for the medicinal chemists to design and develop more potent flavonoid-type inhibitors against EcGUS.

A rapid and sensitive liquid chromatography with tandem mass spectrometry (LC-MS/MS) method was developed and validated for the simultaneous determination of luteolin, luteolin-7-O-β-D-glucopyranoside, physalin A, physalin D and physalin L in rat plasma. Scutellarein and dexamethasone were used as the internal standards (IS). Plasma samples were prepared by liquid-liquid extraction with ethyl acetate. The five constituents were separated on an Acquity UPLC BEH C18 column (100 mm × 2.1 mm, 1.7 μm). A gradient elution procedure was used with acetonitrile (A)-0.1% aqueous formic acid (B). Mass spectrometric detection was performed in negative ion multiple reaction monitoring mode with an electrospray ionization (ESI) source. This method showed good linearity (r2 > 0.997) over a concentration range of 2.0-500 ng/mL with a lower limit of quantification of 2.0 ng/mL for all five compounds. The inter- and intra-day accuracy ranged from 91.7 to 104%, and precisions (RSD) were 85%. This validated method was successfully applied for the first time to the pharmacokinetic study of five ingredients after oral administration of 70% ethanol extract of Chinese lantern in rats.

Ten flavonoids belonging to the subclasses of flavones, flavanones and aurones were isolated from methanolic extract of Cirsium palustre leaves after multistep chromatographic separation. Their structures were elucidated with spectroscopic methods. All compounds, except for luteolin 7-O-glucoside, were isolated for the first time. Four compounds—eriodictyol 7-O-glucoside (6), 6-hydroxyluteolin 7-O-glucoside (11), scutellarein 7-O-glucoside (12) and pedalitin (14)—were tested for their effect on collagen expression in normal human dermal fibroblasts. Among them, compound 11 at 40 μM and compound 14, at all concentrations used (1, 20, 40 μM), significantly enhanced the level of total collagen secreted into the medium. Furthermore, compound 11 significantly stimulated type I collagen expression, whereas compound 14 activated type I and III collagen expression at the mRNA level, depending on concentration. MMP-2 activity was inhibited by all study compounds, with the greatest effect recorded with compound 14 at 20 μM. The lack of effect on collagen content in the medium of compound 6- and compound 12-treated cells, besides an increase in COL1A1 and COL1A2 expression, might be caused by diminished expression of HSP47 gene, resulting in decreased procollagen secretion. Future study of compounds 11 and 14 for their potential therapeutic use in conditions connected with collagen biosynthesis deficiency is required. Copyright © 2014 John Wiley & Sons, Ltd.

Scutellarin had protective effects against neuronal injury, however, there are few studies on the protective effect of scutellarein, which is the main metabolite of scutellarin in vivo. This study investigated whether the neural injury by ischemia/reperfusion would be influenced by different doses of scutellarin and scutellarein. Male Wistar rats were orally administered with scutellarin and scutellarein at the doses of 0.09, 0.17, 0.35, 0.70, 1.40 mmol/kg, respectively; then after six consecutive days, they were subjected to global ischemia by occlusion of the bilateral common carotid arteries (BCCAO). After reperfusion for about 21 h, neurological and histological examinations were performed. The present results showed that scutellarein attenuated neuronal cell damage, reduced cerebral water content, regulated the expression of glutamic acid (Glu), aspartic acid (Asp), glycine (Gly), γ-aminobutyric acid (GABA) and taurine (Tau), and improved the Ca(2+)-ATPase and Na(+),K(+)-ATPase activity. Meanwhile, significant difference was found among various doses of scutellarin and scutellarein. Our studies indicated that scutellarin and scutellarein could improve neuronal injury, and scutellarein had better protective effect than scutellarin in rat cerebral ischemia.

Scutellarin (SG) and its aglycone, Scutellarein (S), are flavonoids of therapeutic cardiocerebrovascular disease. SG was hydrolyzed by bacterial enzyme into S which was absorbed in the intestine. The aim of this study was to determine the effects of the microflora in the intestinal lumen and the efflux transporter of intestinal epithelial cells on the absorption process of SG and S. After oral administration of antibiotics in Sprague-Dawley rats, the reduced bacterial enzyme formation significantly hinders the absorption of SG, whereas scarcely that of S. The absorption study in situ single-pass intestinal perfusion revealed that S could be absorbed throughout the intestine of rats. The effective intestinal permeability of S in the jejunum was much lower than in the other sections of the GI tract. The efflux transporter promoted SG secretion into lumen from enterocytes, which hindered the absorption of both SG and S into the bloodstream. The efflux transporter protein inhibitor (verapamil, probenecid and reserpine) remarkably enhanced the absorption of S and the bioconversion of S into SG in both the rat intestine and Caco-2-monolayer models.

Four novel 2-styrylchromones, 4′,5,7-trihydroxy-6-isopentene-2-styrylchromone (1), 4′,5,7-trihydroxy-8-isopentene-2-styrylchromone (2), 4′,5,7-trihydroxy-6-(2-hydroxy-3-methylbut-3-enyl)-2-styrylchromone (3) and 4′,5,7-trihydroxy-8-(2-hydroxy-3-methylbut-3-enyl)-2-styrylchromone (4), were isolated from shed bark of Platanus × acerifolia (Aiton) Willd., as well as four known compounds, 4′,5,7-trihydroxy-2-styrylchromone (5), scutellarein (6), 4′,5,7-trihydroxy-6-prenylflavone (7), and 4′,5,7-trihydroxy-8-prenylflavone (8). The structures of compounds 1–4 were established by direct interpretation of their spectral data, mainly high resolution electrospray ionization mass spectrometry (HR-ESI-MS), 1D and 2D NMR (1H–1H COSY, HSQC and HMBC). The cytotoxicity of the compounds 1–8 was evaluated in four human carcinoma cell lines, including HepG2, SMMC-7721, MDA-MB-231, and KB. Compounds 1–4 exhibited significantly cytotoxic activity toward HepG2 and KB cells, with IC50 values ranging from 3.0 to 9.7 μM.

Scutellarin is an important bioactive flavonoid extracted from Erigeron breviscapus (Vant.) Hand-Mazz, and scutellarein is the corresponding aglycone of scutellarin. The present study aims to compare the inhibition potential of scutellarin and scutellarein towards several important UDP-glucuronosyltransferase (UGT) isoforms, including UGT1A1, UGT1A6, UGT1A9 and UGT2B7. It was demonstrated that scutellarein exerted stronger inhibition towards the tested UGT isoforms than scutellarin. Furthermore, the inhibition kinetic type and parameters (K-i) were determined for the scutellarein's inhibition towards these UGT isoforms. Competitive inhibition of scutellarein towards all these UGT isoforms was demonstrated, and the K-i values were calculated to be 0.02, 5.0, 5.8 and 35.9 mu M for UGT1A1, 1A6, 1A9 and 2B7, respectively. Using in vivo maximum plasma concentration of scutellarein in rat, the in vitro-in vivo extrapolation was performed to predict in vivo situation, indicating the most possible in vivo adverse effects due to the inhibition of scutellarein towards UGT1A1. All these results remind us to monitor the utilization of scutellarin and scutellarein, and the herbs containing these two components. Copyright (c) 2013 John Wiley & Sons, Ltd.

Background Glycosylation of flavonoids is a promising approach to improve the pharmacokinetic properties and biological activities of flavonoids. Recently, many efforts such as enzymatic biocatalysis and the engineered Escherichia coli biotransformation have increased the production of flavonoid glucosides. However, the low yield of flavonoid glucosides can not meet the increasing demand for human medical and dietary needs. Saccharomyces cerevisiae is a generally regarded as safe (GRAS) organism that has several attractive characteristics as a metabolic engineering platform for the production of flavonoid glucosides. However, endogenous glucosidases of S.cerevisiae as a whole-cell biocatalyst reversibly hydrolyse the glucosidic bond and hinder the biosynthesis of the desired products. In this study, a model flavonoid, scutellarein, was used to exploit how to enhance the production of flavonoid glucosides in the engineered S.cerevisiae. Results To produce flavonoid glucosides, three flavonoid glucosyltransferases (SbGTs) from Scutellaria baicalensis Georgi were successfully expressed in E. coli, and their biochemical characterizations were identified. In addition, to synthesize the flavonoid glucosides in whole-cell S. cerevisiae, SbGT34 was selected for constructing the engineering yeast. Three glucosidase genes (EXG1, SPR1, YIR007W) were knocked out using homologous integration, and the EXG1 gene was determined to be the decisive gene of S. cerevisiae in the process of hydrolysing flavonoid glucosides. To further enhance the potential glycosylation activity of S. cerevisiae, two genes encoding phosphoglucomutase and UTP-glucose-1-phosphate uridylyltransferase involved in the synthetic system of uridine diphosphate glucose were over-expressed in S. cerevisiae. Consequently, approximately 4.8 g (1.2 g/L) of scutellarein 7-O-glucoside (S7G) was produced in 4 L of medium after 54 h of incubation in a 10-L fermenter while being supplied with ~3.5 g of scutellarein. Conclusions The engineered yeast harbouring SbGT with a deletion of glucosidases produced more flavonoid glucosides than strains without a deletion of glucosidases. This platform without glucosidase activity could be used to modify a wide range of valued plant secondary metabolites and to explore of their biological functions using whole-cell S. cerevisiae as a biocatalyst. Electronic supplementary material The online version of this article (doi:10.1186/s12934-016-0535-2) contains supplementary material, which is available to authorized users.

Oroxylin A and hispidulin, compounds which are abundant in both Scutellaria and liverwort species, are important lead compounds for the treatment of ischemic cerebrovascular disease. Their enzymatic synthesis requires an O-methyltransferase able to interact with the related flavonoid's 6-OH group, but such an enzyme has yet to be identified in plants. Here, the gene encoding an O-methyltransferase (designated PaF6OMT) was isolated from the liverwort species Plagiochasma appendiculatum. A test of alternative substrates revealed that its strongest preferences were baicalein and scutellarein, which were converted into, respectively, oroxylin A and hispidulin. Allowed a sufficient reaction time, the conversion rate of these two substrates was, respectively, 90% and 100%. PaF6OMT offers an enzymatic route to the synthesis of oroxylin A and hispidulin.

Scope Polymethoxylated flavonoids are present in citrus fruit in a range of chemical structures and abundance. These compounds have potential for anticarcinogenesis, antitumor, and cardiovascular protective activity, but the effect on angiogenesis has not been well studied. Methods and results Human umbilical vein endothelial cells (HUVECs) in vitro and zebrafish (Danio rerio) in vivo models were used to screen and identify the antiangiogenesis activity of seven polymethoxylated flavonoids; namely, hesperetin, naringin, neohesperidin, nobiletin, scutellarein, scutellarein tetramethylether, and sinensetin. Five, excluding naringin and neohesperidin, showed different degrees of potency of antiangiogenesis activity. Sinensetin, which had the most potent antiangiogenesis activity and the lowest toxicity, inhibited angiogenesis by inducing cell cycle arrest in the G0/G1 phase in HUVEC culture and downregulating the mRNA expressions of angiogenesis genes flt1, kdrl, and hras in zebrafish. Conclusion The in vivo structure–activity relationship (SAR) analysis indicated that a flavonoid with a methoxylated group at the C3′ position offers a stronger antiangiogenesis activity, whereas the absence of a methoxylated group at the C8 position offers lower lethal toxicity in addition to enhancing the antiangiogenesis activity. This study provides new insight into how modification of the chemical structure of polymethoxylated flavonoids affects this newly identified antiangiogenesis activity.

Graphical abstract, Severe acute respiratory syndrome (SARS) is an infectious disease with a strong potential for transmission upon close personal contact and is caused by the SARS-coronavirus (CoV). However, there are no natural or synthetic compounds currently available that can inhibit SARS-CoV. We examined the inhibitory effects of 64 purified natural compounds against the activity of SARS helicase, nsP13, and the hepatitis C virus (HCV) helicase, NS3h, by conducting fluorescence resonance energy transfer (FRET)-based double-strand (ds) DNA unwinding assay or by using a colorimetry-based ATP hydrolysis assay. While none of the compounds, examined in our study inhibited the DNA unwinding activity or ATPase activity of human HCV helicase protein, we found that myricetin and scutellarein potently inhibit the SARS-CoV helicase protein in vitro by affecting the ATPase activity, but not the unwinding activity, nsP13. In addition, we observed that myricetin and scutellarein did not exhibit cytotoxicity against normal breast epithelial MCF10A cells. Our study demonstrates for the first time that selected naturally-occurring flavonoids, including myricetin and scultellarein might serve as SARS-CoV chemical inhibitors.

Erigeron breviscapus has been widely used in traditional Chinese medicine (TCM) and its total flavonoid component is commonly used to treat ischemic stroke, coronary heart disease, diabetes and hypertension. Scutellarin is the major ingredient of E. breviscapus and scutellarein is one of the main bioactive metabolites of scutellarin in vivo, but the latter's pharmacological activities have not been fully characterized. Provided evidence that could inhibit platelet aggregation, the effect of scutellarein on rat washed platelets and its underlying mechanisms were evaluated in our research. Scutellarein inhibited platelet adhesion and aggregation induced by multiple G protein coupled receptor agonists such as thrombin, U46619 and ADP, in a concentration-dependent manner. Furthermore, the mild effect of scutellarein on intracellular Ca(2+) mobilization and cyclic AMP (cAMP) level was observed. On the other hand, the role of scutellarein as potential protein kinase C (PKC) inhibitor was confirmed by PKC activity analysis and molecular docking. The phorbol myristate acetate-induced platelets aggregation assay with or without ADP implied that the scutellarein takes PKC(s) as its primary target(s), and acts on it in a reversible way. Finally, scutellarein as a promising agent exhibited a high inhibition effect on ADP-induced platelet aggregation among its analogues. This study clarifies the PKC-related signaling pathway involved in antiplatelet action of scutellarein, and may be beneficial for the treatment of cardiovascular diseases.

Three series of scutellarein derivatives have been designed and synthesized based on metabolic mechanism of scutellarin (1) in vivo. Their thrombin inhibition activities were tested through the analyzation of prothrombin time (PT), activated partial thromboplastin time (APTT), thrombin time (TT), and fibrinogen (FIB). The antioxidant activities of these target products were assessed by 1,1-diphenyl-2-picrylhydrazyl radical (DPPH) assay and the ability to protect PC12 cells against H2 O2 -induced cytotoxicity, and their solubilities were evaluated by ultraviolet (UV) spectrophotometer. The results showed that the two isopropyl groups substituted derivative (18c) demonstrated stronger anticoagulant activity, better water solubility, and good antioxidant activity compared with scutellarein (2), which warrants further development of 18c as a promising agent for ischemic cerebrovascular disease treatment.

Scutellarein, the main metabolite of scutellarin in vivo, has relatively better solubility, bioavailability and bio-activity than scutellarin. However, it is very difficult to obtain scutellarein in nature compared with scutellarin. Therefore, the present study focused on establishing an efficient route for the synthesis of scutellarein by hydrolyzing scutellarin. The in vitro antioxidant activities of scutellarein were evaluated by measuring its scavenging capacities toward DPPH, ABTS(+•), (•)OH free radicals and its protective effect on H(2)O(2)-induced cytotoxicity in PC12 cells using MTT assay method. The results showed that essential point to the synthesis was the implementation of H(2)SO(4) in 90% ethanol in N(2) atmosphere; scutellarein had stronger antioxidant activity than scutellarin. The results have laid the foundation for further research and the development of scutellarein as a promising candidate for ischemic cerebrovascular disease.

Pakisides A and B (1 and 2, resp.), new catalpol-type iridoid glycosides, and a new glycoside, 3, of scutellarein have been isolated from the AcOEt-soluble fraction of the whole plant of Abutilon pakistanicum, along with buddlejoside and lapachol. The structures of new compounds were elucidated by spectroscopic techniques including 1H-and 13C-NMR (DEPT), and 2D-NMR experiments.