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Strigolactones (SLs) are natural products with promising applications as agrochemicals to prevent infestation with parasitic weeds due to their ability to trigger seed germination. However, their use is still limited because of the low yields in which they are isolated from natural sources. As such, numerous studies have led to strategies for obtaining them, and various structural analogues, by organic synthesis. These analogues have focused attention on the study of SLs, as some of them are easier to synthesize and possess enhanced properties, such as the level of bioactivity. This review provides an overview of the synthesis of SLs, subsequently focusing on the production of analogues with the canonical structure. The germinating activity of the compounds is also described herein, with positive effects on different species of the problematic genera Striga, Orobanche and Phelipanche having been found. The highly active analogue GR24 is currently the most widely studied in the literature, and relevant structural-activity relationships have been proposed as a result of the study of derivatives functionalized in different positions. Analogues based on other natural SLs such as strigol and orobanchol have also been developed, as have some novel canonical SLs derived from eudesmanolide or guaianolide sesquiterpene lactones. This review aims to provide useful information for the development of bioactive compounds applicable in new generation herbicides, in an attempt to employ similar compounds to those produced naturally in ecosystems that provoke effective herbicide effects at low concentrations.

Yucca is one of the main sources of steroidal saponins, hence different extracts are commercialized for use as surfactant additives by beverage, animal feed, cosmetics or agricultural products. For a deeper understanding of the potential of the saponins that can be found in this genus, an exhaustive review of the structural characteristics, bioactivities and analytical methods that can be used with these compounds has been carried out, since there are no recent reviews on the matter. Thus, a total of 108 saponins from eight species of the genus Yucca have been described. Out of these, the bioactivity of 68 saponins derived from the isolation of Yucca or other genera has been evaluated. Regarding the evaluation and quality control of the saponins from this genus LC-MS technique is the most often used. Nevertheless, the development of methods for their routine analysis in commercial preparations are needed. Moreover, most of the studies found in the literature have been carried out on Y. schidigera extract, since is the most often used for commercial purposes. Only eight of the 50 species that belong to this genus have been studied, which clearly indicates that the identification of saponins present in Yucca genus is still an unresolved question.

Even today, weeds continue to be a considerable problem for agriculture. The application of synthetic herbicides produces serious environmental consequences, and crops suffer loss of their activity due to the appearance of new resistant weed biotypes. Our aim is to develop new effective natural herbicides that improve the problem of resistance and do not harm the environment. This work is focused on a bioassay-guided isolation and the characterization of natural products present in Moquiniastrum pulchrum leaves with phytotoxic activity and its preliminary application in weeds. Moquiniastrum pulchrum was selected for two reasons: it is an abundant species in the Cerrado region (the second most important ecosystem in Brazil, after the Amazon)-the explanation behind its being a dominant species is a major focus of interest-and it has traditional employment in folk medicine. Six major compounds were isolated in this plant: one flavone and five diterpenes, two of which are described for the first time in the literature. Four of the six compounds exhibited phytotoxic activity in the bioassays performed. The results confirmed the phytotoxic potential of this plant, which had not been investigated until now.

Aminophenoxazinones are degradation products resulting from the metabolism of different plant species, which comprise a family of natural products well known for their pharmacological activities. This review provides an overview of the pharmacological properties and applications proved by these compounds and their structural derivatives during 2000-2021. The bibliography was selected according to our purpose from the references obtained in a SciFinder database search for the Phx-3 structure (the base molecule of the aminophenoxazinones). Compounds Phx-1 and Phx-3 are among the most studied, especially as anticancer drugs for the treatment of gastric and colon cancer, glioblastoma and melanoma, among others types of relevant cancers. The main information available in the literature about their mechanisms is also described. Similarly, antibacterial, antifungal, antiviral and antiparasitic activities are presented, including species related directly or indirectly to significant diseases. Therefore, we present diverse compounds based on aminophenoxazinones with high potential as drugs, considering their levels of activity and few adverse effects.

In the search of new alternatives for weed control, spices appear as an option with great potential. They are rich in bioactive natural products and edible, which might minimize toxicity hazard. Marjoram (Origanum majorana L.) is an aromatic herb that has been widely employed as a seasoning herb in Mediterranean countries. Although marjoram boasts a plethora of therapeutic properties (painkiller, antibiotic, treatment for intestinal disorders, etc.), the potential for its extracts for weed control is still to be more thoroughly explored. In order to determine their phytotoxic potential, marjoram leaves were subjected to different bioguided extraction processes, using water, ethyl acetate, acetone or methanol. The most active extract (acetone) was sequentially fractionated to identify its most active compounds. This fractionation led to the isolation and identification of 25 compounds that were classified as monoterpenes, diterpenes or flavonoids. Among them, a new compound named majoradiol and several compounds are described in marjoram for the first time. The phytotoxicity of the major compounds to etiolated wheat coleoptiles was compared against that of the commercial herbicide (Logran(R)), with similar or higher activity in some cases. These results confirm the extraordinary potential of the extracts from this edible plant to develop safer and more environmentally friendly herbicides.

C-17-sesquiterpenoids are a group of natural products that have been recently discovered. These compounds have the peculiarity of lacking the alpha,beta-methylene butyrolactone system, which is known to be quite relevant for many of the biological activities reported for sesquiterpene lactones. Unfortunately, the biological interest of C-17-sesquiterpenoids has not been studied in-depth, mainly due to the poor isolation yields in which they can be obtained from natural sources. Therefore, in order to allow a deeper study of these novel molecules, we have worked out a synthetic pathway that provides C-17-sesquiterpenoids in enough quantities from easily accessible sesquiterpene lactones to enable a more thorough investigation of their bioactivities. With this synthesis method, we have successfully synthesized, for the first time, three natural C-17-sesquiterpenoids, pertyolides A, B, and C, with good overall yields. Furthermore, we have also evaluated their phytotoxicity against etiolated wheat coleoptiles and corroborated that pertyolides B and C present strong phytotoxic activity.

Breviones are a new family of secondary metabolites that were originally isolated from the New Zealand endemic fungus Penicillium brevicompactum var. Dierckx. These compounds are generally characterized by a new carbon skeleton, known as breviane, which that has three possible structural variations, such as breviane, abeo-breviane, and abeo-norbreviane. Brevianes present a basic diterpenic tricyclic core that is mevalonic in origin and is similar to that of perhydrophenanthrene. The core bears four methyl groups at positions C4, C8, C10, and C13 and has defined stereochemistry at positions C5, C8, C9, C10, and C14. The C1'-C7' side chain has been proposed to have a polyketide biosynthetic origin and is joined to the diterpenic moiety through carbons C2'-C15'. The cyclization and lactonization of this part of the molecule leads to the characteristic breviane spiranic ring fused to the α-pyrone.

Naphthotectone is a quinone isolated recently from teak extracts of Tectona grandis. It has been shown to be one of the most abundant compounds and the most active compound isolated form teak. Thus, it has been proposed that naphthotectone is one of the compounds responsible for the allelophathic activity of this plant. An efficient total synthesis of (±) -naphthotectone was achieved in seven steps and 31% overall yield. The best results were obtained by using an aqueous Wittig reaction as a key step. Other reactions used were the formation of an epoxide ring by the Corey– Chaykovsky method, and an innovative one-pot anodic electrooxidation and demethylation.

Four novel compounds (1−4) with an unprecedented skeleton that combines a sesquiterpene lactone and a kaurane diterpene acid were isolated from Helianthus annuus L. var. Arianna extract, which was obtained under supercritical conditions. The structures of 1− 4 were elucidated by NMR and MS analyses. The biosynthetic routes involve sesquiterpene lactones and kauranic acid, both of which were previously isolated from this species.

Decachaeta, Salvia and Podachaenium genera are known for their wide variety of biological activities. Synthetic herbicides have caused a variety of environmental and resistance problems. Natural products represent an important alternative to combat such issues. Sesquiterpene lactones and diterpenes are families of bioactive natural products for which a range of activities have been described. The bioactivities of nine sesquiterpene lactones, eight heliangolides, one guaianolide and twenty two diterpenes isolated from species of the Decachaeta, Salvia and Podachaenium genera were tested by applying a methodical procedure that involves assays of compounds on etiolated wheat coleoptiles (Triticum aestivum), Standard Target Species (STS) and two important weeds (barnyardgrass and brachiaria). The results clearly show that all of the sesquiterpene lactones studied were active on coleoptiles. In addition, six lactones were phytotoxic on both STS and weeds, meaning that these compounds could be used in the development of natural herbicide models.

Bioactive natural products are a potential source of new pharmaceuticals since they offer new modes of action and more specific activities. The use of derivatization also enables the optimal structure for their biological activity to be determined. In this study several epoxycurcuphenol derivatives were synthesized. The substitution pattern on the aromatic and oxirane rings was varied along with that at the benzylic position and the length of the side chain was altered. These changes were made in order to gain a deeper understanding of the structural requirements for activity. The biological activities of these compounds were evaluated on the human leukemia cell line Jurkat using an antiproliferative assay. The activity results and structural requirements are discussed.

The citrus by-products released from citrus processing plants may contain high levels of potentially bioactive compounds such as flavonoids, which are a widely distributed group of polyphenolic compounds with health-related properties based on their antioxidant activity. In the study reported here, the potential bioactivities and antioxidant activities of extracts, fractions and compounds from citrus by-products were evaluated along with the chemical interactions of binary mixtures of compounds and complex mixtures. The bioactivities and interactions were evaluated in wheat coleoptile bioassays and the antioxidant activity was evaluated by the al DPPH (2,2-diphenyl-1-picrylhdrazyl radical) radical scavenging assay. The extracts, fractions and most of the isolated compounds (mainly polymethoxyflavones) showed high activity in the wheat coleoptile bioassay. However, the antioxidant activity was not consistently high, except in the acetone extract fractions. Moreover, a study of the interactions with binary mixtures of polymethoxyflavones showed the occurrence of synergistic effects. The complex mixtures of fractions composed mainly of polymethoxyflavones caused a synergistic effect when it was added to a bioactive compound such as anethole. The results reported here highlight a new application for the wheat coleoptile bioassay as a quick tool to detect potential synergistic effects in compounds or mixtures.

A phytochemical study on the most bioactive extract from Tectona grandis led to the isolation of two new norlignans, tectonoelin A and tectonoelin B, together with ten known compounds. The structures of the compounds were determined by a combination of 1D and 2D NMR techniques. This is the first time that this type of compound (C8–C80 linkage norlignans) has been isolated from a dicotyledon. The general bioactivities of the isolated compounds have been studied using etiolated wheat coleoptiles. The activities showed that the isolated lignans and norlignans should be part of the defence mechanisms of this plant.

tThe work described here is a continuation of a previous study centered on the extraction, using super-critical carbon dioxide, of bioactive substances from sunflower leaves of the Helianthus annuus L. varietyArianna. In this study the addition of 9% of ethanol as co-solvent was analyzed. The extraction was carriedout (P = 100/400 bar, T = 35/55◦C, ethanol = 9%) in order to analyze the influence of pressure, temperatureand sample pre-treatment on the extraction yield and bioactivity of the extracts. The addition of 9% ofethanol to the supercritical solvent enhanced both the extraction yield and the biological activity of theextracts. The best conditions were a pressure of 400 bar and a temperature of 55◦C. In an effort to improvethe bioactivity of the extract, a cascade fractionation of the extracts was carried out and this gave differ-ent results in terms of biological activities and extraction yields. The phytochemical compositions of theextracts were analyzed by thin layer chromatography. The fractionation that gave the best results wascarried out at 90 bar and 40◦C in the first separator. Finally, the effect of extracts on the growth of seedsfrom different plants was analyzed.

Cardoon (Cynara cardunculus L.) is a native plant to the Iberian Peninsula and the European Atlantic coast and invasive in American environments. Different solvents were used to perform cardoon extracts that were tested in phytotoxic bioassays. The ethyl acetate extract had the highest inhibitory activity so this was tested on the germination and growth of standard target species (lettuce, watercress, tomato, and onion) and weeds (barnyardgrass and brachiaria). The ethyl acetate extract was very active on root growth in both standard target species and weeds and it was therefore fractionated by chromatography. The spectroscopic data showed that the major compounds were sesquiterpene lactones. Aguerin B, grosheimin, and cynaropicrin were very active on etiolated wheat coleoptile, standard target species, and weed growth. The presence of these compounds explains the bioactivity of the ethyl acetate extract. The strong phytotoxicity of these compounds on important weeds shows the potential of these compounds as natural herbicide models.

Four triterpenoid saponins (1–4) were isolated from the aerial parts of Trifolium argutum Sol. (sharptooth clover) and their structures were elucidated by comprehensive spectroscopic analysis, including 1D and 2D NMR techniques, mass spectrometry and chemical methods. Two of them are new compounds, characterized as 3-O-[α-L-rhamnopyranosyl-(1→2)-β-D-galactopyranosyl-(1→2)-β-D-glucuronopyra- nosyl]-3β,24-dihydroxyolean-12-ene-22-oxo-29-oic acid (1) and 3-O-[β-D-galactopyranosyl-(1→2)- β-D-glucuronopyranosyl]-3β,24-dihydroxyolean-12-ene-22-oxo-29-oic acid (2). The occurrence of 3β,24-dihydroxyolean-12-ene-22-oxo-29-oic acid (melilotigenin) in its natural form is reported for the first time as a triterpenoid aglycone within Trifolium species. The phytotoxicity of compounds was evaluated on four STS at concentration 1 μM to 333 mM. Compound 1 was the most active, showing more than 60% inhibition on the root growth of L. sativa at the higher dose, with IC50 (254.1 μM) lower than that of Logran1 (492.6 μM), a commercial herbicide used as positive control. The structure–activity relationships indicated that both aglycones and glycosidic parts may influence the phytotoxicity of saponins.

A bio-guided optimization of the extraction of bioactive components from Annona glabra leaves has been developed using the etiolated wheat coleoptile bioassay as the control method. The optimization of an ultrasound-assisted extraction of bioactive compounds using allelopathy results as target values has been carried out for the first time. A two-level fractional factorial experimental design was applied to optimize the ultrasound-assisted extraction. The solvent was the extraction variable that had the most marked effect on the resulting bioactivity of the extracts in the etiolated wheat coleoptile bioassay. Extraction time, extraction temperature and the size of the ultrasonic probe also influenced the bioactivity of the extracts. A larger scale extraction was carried out in the next step in the allelopathic study, i.e., the isolation of compounds from the bioactive extract and chemical characterization by spectroscopic techniques, including NMR. Eight compounds were isolated and identified from the active extracts, namely two steroids (β-sistosterol and stigmasterol), five diterpenes with the kaurane skeleton (ent-kaur-16-en-19-oic acid, ent-19-methoxy-19-oxokauran-17-oic acid, annoglabasin B, ent-17-hydroxykaur-15-en-19-oic acid and ent-15β,16β-epoxy-17-hydroxy-kauran-19-oic acid) and the acetogenin asimicin. The most active compound was annoglabasin B, which showed inhibition with values of -95% at 10-3 M, -87% at 5 - 10-4 M and greater than -70% at 10-4 M in the etiolated wheat coleoptile bioassay.

Guaianolides constitute a large and diverse group of biologically active sesquiterpenes. Guaianolide and seco-guaianolides can also be used as, for example, scaffolds for the development of new active molecules that are readily accessible by synthetic methods. Nevertheless, these lactones often have complex structures that make their synthesis difficult. The aim of this microreview is to provide an overview of the developments in guaianolide synthesis by the two major synthetic strategies: semi-synthesis and total synthesis. Partial and total syntheses of guaianolides are described, with particular emphasis placed on the methods reported in the last decade. The methods discussed include rearrangements, cycloadditions, ring-closing metathesis, the use of transitionmetal catalysts, photochemical reactions, and other recently developed techniques as key steps.

Seven previously unreported triterpene glycosides (1−7) were isolated from methanol extract of the aerial parts of Trifolium medium var. sarosiense (zigzag clover). Their structures were established by the extensive use of 1D and 2D NMR experiments along with ESI-MS and HRMS analyses. Compounds 1−7 are oleanane derivatives characterized by the presence of a keto group at C-22 of an aglycone and a primary alcoholic function at C-24 and differing functions at C-30. Among these, compounds 1−3 and 6 showed a secondary alcoholic function at C-11, which is methoxylated in compounds 4 and 7. Compound 5 was shown to possess a known aglycone, wistariasapogenol A; however, it is described here for the first time as a saponin constituent of the Trifolium genus. Some aspects of taxonomic classification of zigzag clover are also discussed.

La Alelopatía es: “la ciencia que estudia procesos que implican metabolitos secundarios producidos por plantas, algas, bacterias y hongos que influyen en el crecimiento y desarrollo de sistemas cultivados y biológicos” y en el que, por tanto, se incluye cualquier interacción de las plantas con su medio ambiente. En los últimos años, se viene desarrollando la búsqueda de nuevos herbicidas basados en metabolitos secundarios producidos por plantas que sean respetuosos con el medio ambiente, de buena degradabilidad, atóxicos para el ser humano, y que presenten la mejor respuesta posible ante los actuales, y cada vez más frecuentes, fenómenos de resistencia. Los productos naturales de origen vegetal se presentan como una fuente atractiva de sustancias agroquímicas, no sólo por su diversidad estructural, sino por su acción biológica específica y su carácter inocuo “a priori” para el medio ambiente. Dentro de estos productos naturales vegetales de elevada actividad, se destacan los ácidos benzohidroxámicos (metabolitos secundarios con esqueletos de (2H)-1,4-benzoxacin-3(4H)-ona), que además, se trata de uno de los grupos de aleloquímicos mayormente estudiados. Entre los de mayor interés, se encuentra el D-DIBOA (4-hidroxi-(2H)-1,4-benzoxacin-3(4H)-ona), que presenta elevadas fitotoxicidad y estabilidad y muy buena degradabilidad en suelos de cultivo. Además, la producción de 6-Cl-D-DIBOA presenta alta actividad y 8-Cl-D-DIBOA alta selectividad frente a diferentes especies. La síntesis de ácidos benzohidroxámicos (benzoxacinonas) tiene lugar en dos etapas. La primera de ellas consiste en una reacción de sustitución nucleofílica de los productos comerciales derivados del 2-nitrofenol con diferentes sustituyentes en el anillo bencénico. La segunda etapa se trata de una reacción de reducción del grupo nitro aromático. Debido al riesgo de explosión que implica la segunda etapa de reacción, que se trata de una reacción de catálisis heterogénea exotérmica con desprendimiento de h, Allelopathy is: “the science that studies processes where secondary metabolites produced by plants, algae, bacteria and fungi and that influences the growth and development of cultivated and biological systems” and where we therefore, include whatever interaction between plants and their environment. During the last years, a search for new herbicides based on plants secondary metabolites, has been developed. These must be eco-friendly, must have a good degradability, and they also have to be non-toxic for human beings and effective against the increasingly resistance phenomena. Natural products arise as an attractive source of agrochemical substances, not only because of their structural diversity, but because of their specific biological action and their “a priori” harmless nature towards their environment. We highlight benzohydroxamic acids (secondary metabolites with a (2H)-1,4-benzoxazin-3(4H)-one skeleton)as natural compounds that come from plants and have shown a high activity. They are also one of the larger studied allelochemicals’ group. Within the most interesting ones, we can find D-DIBOA (4-hydroxy-(2H)-1,4-benzoxazin-3-(4H)-one), which presents high phytotoxicity and stability, and also a very good degradability in soil. Also, 6-Cl-D-DIBOA has a high activity and 8-Cl-D-DIBOA has a high selectivity towards different species. The chemical synthesis of benzohydroxamic acids (benzoxacinones) takes place within two steps. The first one consists of a nucleophilic substitution by using commercial derivatives of 2-nitrophenol products with different substituents in the benzenic ring. The second step consists of a reduction reaction of the aromatic nitro group. Due to the explosion risk that the second step of the reaction implies (it’s an exothermic heterogeneous catalysis with hydrogen releasing), new alternatives were explored. The second step can be done by the use of E.coli in a biotransformation, as it was concluded in the Collaborative Project “P06-TEP-0

Debido a las numerosas propiedades terapéuticas Aloe Barbadensis, como cicatrizantes, hidratantes digestivas o anti-inflamatorias; se plantea el estudio, aislamiento y determinación estructural de los componentes de su exudado. Este se obtiene al hacer un corte en la hoja, y contiene principalmente antraquinonas y glicósidos de antronas, algunos de ellos con actividad anti-cancerígena reportada. Se realizará también un estudio biodirigido del mismo y se utilizarán técnicas como la resonancia magnética nuclear mono y bidimensional, HPLC/MS e IR para la caracterización molecular.

Aims Benzoxazinones with the 4-hydroxy-(2H)-1,4- benzoxazin-3(4H)-one skeleton have been proposed as potentially successful models for the development of novel design leads. D-DIBOA has proven to be the most promising base structure in the search for novel herbicide models based on the benzoxazinone skeleton. The biodegradation dynamics of D-DIBOA in soil are therefore relevant and are the subject of this study. Methods A previously optimized methodology for the assessment of biodegradation has been applied for the first time to a synthetic benzoxazinone. Results Biodegradability is a characteristic of natural benzoxazinones and a safety requirement for the development of herbicidal chemicals. The biodegradation phenomenon and its consequences for the development of new herbicide models are discussed. The half-life determined for D-DIBOA was much higher than those previously reported for the natural products DIBOA, DIMBOA and their benzoxazolinone derivatives. Conclusions This finding, together with its previously described potent phytotoxicity, suggests that D-DIBOA is a useful candidate for novel herbicide model development. The lactam D-HBOA, which is slightly less phytotoxic than its precursor, was discovered to be the first and principal metabolite resulting from D-DIBOA degradation.

The citrus by-products released from citrus processing plants may contain high levels of potentially bioactive compounds such as flavonoids, which are a widely distributed group of polyphenolic compounds with health-related properties based on their antioxidant activity. In the study reported here, the potential bioactivities and antioxidant activities of extracts, fractions and compounds from citrus by-products were evaluated along with the chemical interactions of binary mixtures of compounds and complex mixtures. The bioactivities and interactions were evaluated in wheat coleoptile bioassays and the antioxidant activity was evaluated by the al DPPH (2,2-diphenyl-1-picrylhdrazyl radical) radical scavenging assay. The extracts, fractions and most of the isolated compounds (mainly polymethoxyflavones) showed high activity in the wheat coleoptile bioassay. However, the antioxidant activity was not consistently high, except in the acetone extract fractions. Moreover, a study of the interactions with binary mixtures of polymethoxyflavones showed the occurrence of synergistic effects. The complex mixtures of fractions composed mainly of polymethoxyflavones caused a synergistic effect when it was added to a bioactive compound such as anethole. The results reported here highlight a new application for the wheat coleoptile bioassay as a quick tool to detect potential synergistic effects in compounds or mixtures.

Guaianolides constitute a large and diverse group of biologically active sesquiterpenes. Guaianolide and seco-guaianolides can also be used as, for example, scaffolds for the development of new active molecules that are readily accessible by synthetic methods. Nevertheless, these lactones often have complex structures that make their synthesis difficult. The aim of this microreview is to provide an overview of the developments in guaianolide synthesis by the two major synthetic strategies: semi-synthesis and total synthesis. Partial and total syntheses of guaianolides are described, with particular emphasis placed on the methods reported in the last decade. The methods discussed include rearrangements, cycloadditions, ring-closing metathesis, the use of transitionmetal catalysts, photochemical reactions, and other recently developed techniques as key steps.

Tithonia diversifolia (Mexican sunflower) is a dominant plant of the Asteraceae family, which suggests it produces allelochemicals that interfere with the development of surrounding plants. The study described herein was conducted to identify the compounds that have phytotoxic activity in T. diversifolia extracts. Ethyl acetate extracts of the leaves, stems, and roots showed significant inhibition of wheat coleoptile growth, and the leaf extract had similar inhibitory effects to a commercial herbicide. Fourteen compounds, 12 of which were sesquiterpene lactones, have been isolated. Two sesquiterpene lactones are reported for the first time and were isolated as an inseparable mixture of 8β-O-(2-methylbutyroyl)- tirotundin (4) and 8β-O-(isovaleroyl)tirotundin (5). Their structures were determined by spectroscopic analysis, including NMR techniques and mass spectrometry. The sesquiterpene lactones 1β methoxydiversifolin (6), tagitinin A (7), and tagitinin C (8) were the major products identified. These compounds were active on etiolated wheat coleoptiles, seed germination, and the growth of STS and weeds. The phytotoxic activity shown by these sesquiterpene lactones indicates that they are the compounds responsible for the activity exhibited by the initial extracts.

The work described herein is a continuation of our initial studies on the supercritical fluid extraction (SFE) with CO2 of bioactive substances from Helianthus annuus L. var. Arianna. The selected SFE extract showed high activity in the wheat coleoptile bioassay, in Petri dish phytotoxicity bioassays, and in the hydroponic culture of tomato seeds. Chromatographic fractionations of the extracts and a spectroscopic analysis of the isolated compounds showed 52 substances belonging to 10 different chemical classes, which were mainly sesquiterpene lactones, diterpenes, and flavonoids. Heliannuol M (31), helivypolides K and L (36, 37), and helieudesmanolide B (38) are described for the first time in the literature. Metabolites have been tested in the etiolated wheat coleoptile bioassay with good results in a noteworthy effect on germination. The most active compounds were also tested on tomato seeds, heliannuol A (30) and leptocarpin (45) being the most active, with values similar to those of the commercial herbicide.

Four triterpenoid saponins (1–4) were isolated from the aerial parts of Trifolium argutum Sol. (sharptooth clover) and their structures were elucidated by comprehensive spectroscopic analysis, including 1D and 2D NMR techniques, mass spectrometry and chemical methods. Two of them are new compounds, characterized as 3-O-[α-L-rhamnopyranosyl-(1→2)-β-D-galactopyranosyl-(1→2)-β-D-glucuronopyra- nosyl]-3β,24-dihydroxyolean-12-ene-22-oxo-29-oic acid (1) and 3-O-[β-D-galactopyranosyl-(1→2)- β-D-glucuronopyranosyl]-3β,24-dihydroxyolean-12-ene-22-oxo-29-oic acid (2). The occurrence of 3β,24-dihydroxyolean-12-ene-22-oxo-29-oic acid (melilotigenin) in its natural form is reported for the first time as a triterpenoid aglycone within Trifolium species. The phytotoxicity of compounds was evaluated on four STS at concentration 1 μM to 333 mM. Compound 1 was the most active, showing more than 60% inhibition on the root growth of L. sativa at the higher dose, with IC50 (254.1 μM) lower than that of Logran1 (492.6 μM), a commercial herbicide used as positive control. The structure–activity relationships indicated that both aglycones and glycosidic parts may influence the phytotoxicity of saponins.

The first total synthesis of speciosins P and G, previously isolated from Hexagonia speciosa, is reported. These compounds have been synthesized by Sonogashira coupling from readily available starting materials. Siccayne was also synthesized from the same starting material in two steps along with a number of other derivatives. The compounds were tested in the wheat coleoptile bioassay. The most active compound was the intermediate 18, followed by 29 and 17. The structural requirements for activity in these compounds are the presence of methoxy groups in the aromatic ring and a formyl or hydroxy group in the side chain.

El sector vitivinícola provoca un gran impacto medioambiental en distintas zonas geográficas debido a la generación de grandes cantidades de residuos provenientes de la vinificación y la destilería durante un corto período de tiempo en el año, generalmente entre Agosto y Octubre; el aprovechamiento y optimización de esos recursos se viene realizando, en mayor o menor medida, desde hace tiempo; no obstante queda mucho por hacer, en particular sobre la caracterización de los mismos buscando nuevas vías de procesado, ampliando la oferta de productos procedentes de los subproductos generados. El objetivo de este trabajo es el estudio de la composición de los residuos de vinificación de dos variedades de uvas cultivadas en la Indicación Geográfica Protegida de Vinos de la Tierra de Cádiz, en concreto la variedad blanca vr. Palomino y la variedad tinta vr. Tempranillo. Para ello se han analizado el nitrógeno orgánico, la fibra alimenticia y los azúcares totales y reductores en los residuos generados en sendos procesos de vinificación, como parámetros indicadores, evaluándose en base a los datos obtenidos sus posibles usos en la industria de la alimentación.

Los ácidos grasos son componentes importantes de los alimentos de origen vegetal y animal, encontrándose principalmente en aceites y grasas de determinados alimentos. Su uso en alimentación está cada vez más extendido debido a las importantes características beneficiosas que presentan. Los residuos obtenidos durante los procesos involucrados en la elaboración de vinos presentan elevadas concentraciones de compuestos de gran valor añadido entre los que se encuentran los ácidos grasos. En el presente trabajo se ha procedido a estudiar el contenido de ácidos grasos de los orujos obtenidos como residuos en la vinificación de cinco variedades de uva, tres blancas (Palomino Fino, Moscatel y Pedro Ximénez) y dos variedades tintas (Tempranillo y Tintilla de Rota) y su relación con el poder antioxidante de los extractos grasos obtenidos de los mismos. Las muestras de orujo obtenidas en los procesos de vinificación de las variedades indicadas se han secado utilizando aire a 40ºC y en oscuridad en una cámara climática habilitada para ello. Posteriormente se han molturado y tamizado hasta un tamaño de grano entre 100 y 300 micras, procediéndose a continuación a la extracción de la fracción lipídica siguiendo dos procedimientos distintos: extracción en continuo con n-hexano para la extracción y análisis de los lípidos apolares y extracción con n-butanol saturado en agua para el estudio de los lípidos totales. Posteriormente las muestras son derivatizadas mediante metilación en medio ácido. El análisis del contenido en ácidos grasos se ha realizado por cromatografía de gases con patrón interno (ácido heptadecanóico C17:0 y ácido heneicosanóico C 21:0). Paralelamente a este estudio se ha determinado el poder antioxidante de los extractos lipídicos obtenidos, mediante el seguimiento espectrofotométrico de la reacción de oxidación de una disolución que contiene la muestra junto con el ABTS (ácido 2,2'-azino-bis(3-etilbentiazolina-6-sulfónico)) por medio de un sistema electrolítico.

Synthetic herbicides represent a serious problem in modern agriculture because they are not biodegradable and can accumulate in the soil and in the groundwater, a situation that allows them to enter the trophic chain and ultimately leads to human exposure. Allelopathic chemicals offer an effective alternative to the synthetic compounds. The aim of this experiment is to highlight the differences between chemical and biological control of diseases in crops and to demonstrate the use of natural fungicides and herbicides as alternatives to synthetic chemicals. The experiment involves an evaluation by students of the potential of plant extracts as an alternative to synthetic agrochemicals to identify new ecological farming techniques that could be applied in agriculture. In an effort to encourage 1800 students in high school (14 to 16 years old) to have an interest in science, technology, and innovation, the third edition of the Summer Science Campus was organized by the Spanish Foundation for Science and Technology and the Ministry of Education, Culture, and Sports with support from the foundation Obra Social “la Caixa”.

The content in secondary metabolites greatly affects the quality of plants used for food consumption. Specifically, the production of defence secondary metabolites is triggered by a number of biotic and abiotic stress factors. Commonly studied biotic factors include insects and other herbivores that cause wounding and tissue damage due to microorganisms. Among abiotic factors, mechanical stress induced in the roots has yet to be studied in depth. Such studies are of interest because of the influence of this factor on plants grown under in vitro conditions. Herein, we present our results on essential oil production and other defence-related morphological traits in terms of the effect of mechanical stress induced in the roots of Mentha pulegium plants grown under different conditions: greenhouse using soil as support and non-soil in vitro conditions using gelose and glass beads. A positive correlation has been found between secondary metabolites production, i.e. essential oil and growth conditions. The presence and development of morphological characteristics linked to their storage and lixiviation into the environment – trichomes and glandular hairs in the leaves; lateral roots and fibrous roots – has also been positively related to an increase in penetration resistance on the roots by the substrate – mechanical impedance. Pulegone is the major defence compound in pennyroyal essential oil. Pulegone production and other essential oil constituents present in trichomes have been quantified under different growth conditions and the results have been correlated with morphological characteristics and growth conditions.

Cardoon (Cynara cardunculus L.) is a native plant to the Iberian Peninsula and the European Atlantic coast and invasive in American environments. Different solvents were used to perform cardoon extracts that were tested in phytotoxic bioassays. The ethyl acetate extract had the highest inhibitory activity so this was tested on the germination and growth of standard target species (lettuce, watercress, tomato, and onion) and weeds (barnyardgrass and brachiaria). The ethyl acetate extract was very active on root growth in both standard target species and weeds and it was therefore fractionated by chromatography. The spectroscopic data showed that the major compounds were sesquiterpene lactones. Aguerin B, grosheimin, and cynaropicrin were very active on etiolated wheat coleoptile, standard target species, and weed growth. The presence of these compounds explains the bioactivity of the ethyl acetate extract. The strong phytotoxicity of these compounds on important weeds shows the potential of these compounds as natural herbicide models.

A bioassay-guided fractionation of Agave offoyana leaves led to the isolation of five steroidal saponins (1–5) along with six known saponins (6–11). The compounds were identified as (25R)-spirost-5-en-2α,3β-diol-12-one 3-O-{α-L-rhamnopyranosyl-(1→3)-O-β-D-glucopyranosyl-(1→2)-O-[β-D-xylopyranosyl-(1→3)]-O-β-D-glucopyranosyl-(1→4)-O-β-D-galactopyranoside} (1), (25R)-spirost-5-en-3β-ol-12-one 3-O-{α-L-rhamnopyranosyl-(1→3)-O-β-D-glucopyranosyl-(1→2)-O-[β-D-xylopyranosyl-(1→3)]-O-β-D-glu copyranosyl-(1→4)-O-β-D-galactopyranoside} (2), (25R)-spirost-5-en-3β-ol-12-one 3-O-{β-D-xylopyrano syl-(1→3)-O-β-D-glucopyranosyl-(1→2)-O-[β-D-xylopyranosyl-(1→3)]-O-β-D-glucopyranosyl-(1→4)-O-β -D-galactopyranoside} (3), (25R)-26-O-β-D-glucopyranosylfurost-5-en-3β,22α,26-triol-12-one 3-O- {α-L-rhamnopyranosyl-(1→3)-O-β-D-glucopyranosyl-(1→2)-O-[β-D-xylopyranosyl-(1→3)]-O-β-D-glucopyrano syl-(1→4)-O-β-D-galactopyranoside} (4) and (25R)-26-O-β-D-glucopyranosylfurost-5-en-3β,22α,26-triol- 12-one 3-O-{β-D-xylopyranosyl-(1→3)-O-β-D-glucopyranosyl-(1→2)-O-[β-D-xylopyranosyl-(1→3)]-O-β- D-glucopyranosyl-(1→4)-O-β-D-galactopyranoside} (5) by comprehensive spectroscopic analysis, including one- and two-dimensional NMR techniques, mass spectrometry and chemical methods. The phytotoxicity of the isolated compounds on the standard target species Lactuca sativa was evaluated.

A bio-guided optimization of the extraction of bioactive components from Annona glabra leaves has been developed using the etiolated wheat coleoptile bioassay as the control method. The optimization of an ultrasound-assisted extraction of bioactive compounds using allelopathy results as target values has been carried out for the first time. A two-level fractional factorial experimental design was applied to optimize the ultrasound-assisted extraction. The solvent was the extraction variable that had the most marked effect on the resulting bioactivity of the extracts in the etiolated wheat coleoptile bioassay. Extraction time, extraction temperature and the size of the ultrasonic probe also influenced the bioactivity of the extracts. A larger scale extraction was carried out in the next step in the allelopathic study, i.e., the isolation of compounds from the bioactive extract and chemical characterization by spectroscopic techniques, including NMR. Eight compounds were isolated and identified from the active extracts, namely two steroids (β-sistosterol and stigmasterol), five diterpenes with the kaurane skeleton (ent-kaur-16-en-19-oic acid, ent-19-methoxy-19-oxokauran-17-oic acid, annoglabasin B, ent-17-hydroxykaur-15-en-19-oic acid and ent-15β,16β-epoxy-17-hydroxy-kauran-19-oic acid) and the acetogenin asimicin. The most active compound was annoglabasin B, which showed inhibition with values of -95% at 10-3 M, -87% at 5 - 10-4 M and greater than -70% at 10-4 M in the etiolated wheat coleoptile bioassay.

Allelopathy is a biological phenomenon in which an organism produces one or more biochemicals that influence the growth, survival, and reproduction of other organisms. Allelopathy has been the subject of a great deal of research in chemical ecology since the 1930s. The characterization of the factors that influence this phenomenon has barely been explored, mainly due to the complexity of this area. The main aim of the research carried out to date has been to shed light on the importance of these interactions in agroecosystems, especially in relation to the interactions between crops and weeds. Herein we report the characterization of a complete allelochemical pathway involving benzoxazinones, which are known to participate in allelopathic plant defense interactions of several plants of high agronomic interest. The production of the defense chemicals by a donor plant (crop), the route and transformations of the chemicals released into the environment, and the uptake and phytotoxic effects on a target plant (weed) were all monitored. The results of this study, which is the first of its kind, allowed a complete dynamic characterization of the allelopathic phenomenon for benzoxazinones.

Onopordum acanthium L. (Asteraceae) is a plant native to southern Europe and southwestern Asia, but it is invasive in disturbed areas and agricultural fields around the world, causing many agronomic problems by interfering with crops or preventing animals from grazing on pastures. Allelopathy could be one of the reasons that this plant has spread over different continents. The aim of the present study was to bioprospect O. acanthium leaf extracts through the isolation and purification of allelopathic secondary metabolites with phytotoxicity to explain their invasive behavior. Phytotoxic activity was tested using etiolated wheat coleoptiles. The most active extract was selected to perform a bioassay-guided isolation of two flavonoids, pectolarigenin (1) and scutellarein 4’-methyl ether (2), and two sesquiterpene lactones, elemanolide 11(13)-dehydromelitensin b-hydroxyisobutyrate (3) and acanthiolide (4). All compounds were isolated for the first time from O. acanthium, and acanthiolide (4) is described for the first time. Compound 3 strongly inhibited the growth of wheat coleoptiles and 1 showed an intermediate effect. The results indicate that these compounds could contribute to the invasion of O. acanthium in ecological systems and agricultural fields.

The bioavailability of soy isoflavones depends on the composition of the microflora for each subject. Bacteria act on different isoflavones with increased or reduced absorption and cause biotransformation of these compounds into metabolites with higher biological activity. S-equol is the most important metabolite and only 25–65 % of the population have the microflora that produces this compound. The presence of equol-producing bacteria in soy product consumers means that the consumption of such products for prolonged periods leads to lower cardiovascular risk, reduced incidence of prostate and breast cancer, and greater relief from symptoms related to the menopause such as hot flushes and osteoporosis.

Bioguided studies of flowers of Agave offoyana allowed the isolation of five steroidal saponins never described previously, Magueyosides A–E (1–5), along with six known steroidal saponins (6–11). The structures of compounds were determined as (25R)-spirost-5-en-2a,3b-diol-12-one 3-O-{b-D-xylopyranosyl-(1-3)-O-b-D-glucopyranosyl-(1-2)-O-[b-D-xylopyranosyl-(1-3)]-O-b-D-glucopyranosyl-( 1-4)-O-b-D-galactopyranoside} (1), (25R)-spirost-5-en-2a,3b-diol-12-one 3-O-{b-D-glucopyranosyl-(1-2)-O-[b-D-xylopyranosyl-(1-3)]-O-b-D-glucopyranosyl-(1-4)-O-b-D galactopyranoside} (2), (25R)-spirost-5-en-2a,3b,12b-triol 3-O-{b-D-glucopyranosyl-(1-2)-O-[b-D-xylopyranosyl-(1-3)]- O-b-D-glucopyranosyl-(1-4)-O-b-D-galactopyranoside} (3), (25R)-5a-spirostan-2a,3b-diol-12-one 3-O-{b-D-xylopyranosyl-(1-3)-O-b-D-glucopyranosyl-(1-2)-O-[b-D-xylopyranosyl-(1-3)]-O-b-D-glucopyranosyl-(1-4)-O-b-D-galactopyranoside} (4), and (25R)-5a-spirostan-2a,3b-diol-9(11)-en-12-one 3-O-{b-D-xylopyranosyl-(1-3)-O-b-D-glucopyranosyl-(1-2)-O-[b-D-xylopyranosyl-(1-3)]-O-b-D-glucopyranosyl-( 1-4)-O-b-D-galactopyranoside} (5), by comprehensive spectroscopic analysis, including one- and two-dimensional NMR techniques, mass spectrometry and chemical methods. The bioactivities of the isolated compounds on the standard target species Lactuca sativa were evaluated. A dosedependent phytotoxicity and low dose stimulation were observed.

Naphthotectone is a quinone isolated recently from teak extracts of Tectona grandis. It has been shown to be one of the most abundant compounds and the most active compound isolated form teak. Thus, it has been proposed that naphthotectone is one of the compounds responsible for the allelophathic activity of this plant. An efficient total synthesis of (±) -naphthotectone was achieved in seven steps and 31% overall yield. The best results were obtained by using an aqueous Wittig reaction as a key step. Other reactions used were the formation of an epoxide ring by the Corey– Chaykovsky method, and an innovative one-pot anodic electrooxidation and demethylation.

The Cerrado (the Brazilian savanna) is one of the vegetation formations of great biodiversity in Brazil and it has experienced strong deforestation and fragmentation. The Cerrado must contain at least 12,000 higher plant species.We discuss the ecological relevance of phytochemical studies carried out on plants from the Cerrado, including examples of phytotoxicity, antifungal, insecticidal and antibacterial activities. The results have been classified according to activity and plant family. The most active compounds have been highlighted and other activities are discussed. A large number of complex biochemical interactions occur in this system. However, only a small fraction of the species has been studied from the phytochemical viewpoint to identify the metabolites responsible for these interactions.

The stressful conditions associated with the Brazilian savanna (Cerrado) environment were supposed to favor higher levels of allelochemicals in Rapanea umbellata from this ecosystem. The allelopathic potential of R. umbellata leaf extracts was studied using the etiolated wheat coleoptile and standard phytotoxicity bioassays. The most active extract was selected to perform a bioassay-guided isolation, which allowed identifying lutein (1) and ( )-catechin (2) as potential allelochemicals. Finally, the general bioactivity of the two compounds was studied, which indicated that the presence of 1 might be part of the defense mechanisms of this plant.