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Sesquiterpene lactones (SLs) are compounds that are highly produced in Cynara cardunculus leaves, known for their phytotoxic activity. This study aims to assess SL-enriched fractions' (cynaropicrin, aguerin B, and grosheimin) phytotoxic potentials and putative modes of action, compared to an initial extract, using two approaches: first, against a panel of nine weed species in pre-emergence, and then on Portulaca oleracea L.'s post-emergency stage. The SL-enriched fractions demonstrated greater phytotoxic activity when compared with the C. cardunculus leaf initial extract. The SL-enriched fractions had higher activity at root growth inhibition over the panel tested, doubling the activity in five of them at 800 ppm. Regarding the post-emergence bioassay, the SL-enriched fractions had a higher influence on the plants' growth inhibition (67% at 800 ppm). The SL-effects on the plants' metabolisms were evidenced. The total chlorophyll content was reduced by 65% at 800 ppm. Oxidative stress induction was observed because of the enhancement in MDA levels at 800 ppm compared to control (52%) and the decrease in SOD-specific activity from 4.20 U/mg protein (400 ppm) to 1.74 U/mg protein (800 ppm). The phytotoxic effects of the SL-enriched fractions suggest that they could be used for a future bioherbicide development.

The phytotoxicities of a selection of eudesmanolides and guaianolides, including natural products and new derivatives obtained by semisynthesis from plant-isolated sesquiterpene lactones, were evaluated in bioassays against three weeds of concern in agriculture ( Amaranthus viridis L., Echinochloa crus-galli L., and Lolium perenne L.). Both eudesmanolides and guaianolides were active against the root and shoot growth of all the species, with the eudesmanolides generally showing improved activities. The IC 50 values obtained for the herbicide employed as positive control (on root and shoot growth, respectively, A. viridis : 27.8 and 85.7 μM; E. crus-galli : 167.5 and 288.2 μM; L. perenne : 99.1 and 571.4 μM) were improved in most of the cases. Structure-activity relationships were discussed, finding that hydroxylation of the A-ring and C-13 as well as the position, number, and orientation of the hydroxyl groups and the presence of an unsaturated carbonyl group can significantly influence the level of phytotoxicity. γ-Cyclocostunolide was the most active compound in the series, followed by others such as dehydrozaluzanin C and α-cyclocostunolide (outstanding their IC 50 values on A. viridis )─natural products that can therefore be suggested as models for herbicide development if further research indicates effectiveness on a larger scale and environmental safety in ecotoxicological assessments.

Six different furanocoumarins were isolated from the aerial parts of Ducrosia anethifolia and tested in vitro for plant cell elongation in etiolated wheat coleoptile. They were also tested for their ability to control three different weeds: ribwort plantain, annual ryegrass, and common purslane. These compounds exhibited strong inhibition of plant cell elongation. In the case of (+)-heraclenin, the IC 50 was lower than 20 μM, indicating a better inhibition than the positive control Logran®. Computational experiments for docking and molecular dynamics revealed for the investigated furanocoumarins bearing an epoxide moiety an improved fitting and stronger interaction with the auxin-like TIR1 ubiquitin ligase. Furthermore, the formed inhibition complex remained also stable during dynamic evaluation. Bidental interaction at the active site, along with an extended hydrogen-bond lifetime, explained the enhanced activity of the epoxides. The in vitro weed bioassay results showed that Plantago lanceolata was the most affected weed for germination, root, and shoot development. In addition, (+)-heraclenin displayed better inhibition values than positive control even at 300 μM concentration., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Sesquiterpene lactones (SLs), plant-derived metabolites with broad spectra of biological effects, including anti-tumor and anti-inflammatory, hold promise for drug development. Primary cilia, organelles extending from cell surfaces, are crucial for sensing and transducing extracellular signals essential for cell differentiation and proliferation. Their life cycle is linked to the cell cycle, as cilia assemble in non-dividing cells of G 0 /G 1 phases and disassemble before entering mitosis. Abnormalities in both primary cilia (non-motile cilia) and motile cilia structure or function are associated with developmental disorders (ciliopathies), heart disease, and cancer. However, the impact of SLs on primary cilia remains unknown. This study evaluated the effects of selected SLs (grosheimin, costunolide, and three cyclocostunolides) on primary cilia biogenesis and stability in human retinal pigment epithelial (RPE) cells. Confocal fluorescence microscopy was employed to analyze the effects on primary cilia formation (ciliogenesis), primary cilia length, and stability. The effects on cell proliferation were evaluated by flow cytometry. All SLs disrupted primary cilia formation in the early stages of ciliogenesis, irrespective of starvation conditions or cytochalasin-D treatment, with no effect on cilia length or cell cycle progression. Interestingly, grosheimin stabilized and promoted primary cilia formation under cilia homeostasis and elongation treatment conditions. Thus, SLs have potential as novel drugs for ciliopathies and tumor treatment.

Aqueous solubility and stability often limit the application of aminophenoxazinones and their sulfur mimics as promising agrochemicals in a sustainable agriculture inspired by allelopathy. This paper presents a solution to the problem using host-guest complexation with cucurbiturils ( CB n ). Computational studies show that CB7 is the most suitably sized homologue due to its strong affinity for guest molecules and its high water solubility. Complex formation has been studied by direct titrations monitored using UV-vis spectroscopy, finding a preferential interaction with protonated aminophenoxazinone species with high binding affinities ( CB7·APOH + , K a = (1.85 ± 0.37) × 10 6 M -1 ; CB7·DiS-NH 3 + , K a = (3.91 ± 0.53) × 10 4 M -1 ; and DiS-(NH 3 + ) 2 , K a = (1.27 ± 0.42) × 10 5 M -1 ). NMR characterization and stability analysis were also performed and revealed an interesting p K a modulation and stabilization by cucurbiturils (2-amino-3 H -phenoxazin-3-one ( APO ), p K a = 2.94 ± 0.30, and CB7·APO, p K a = 4.12 ± 0.15; 2,2'-disulfanediyldianiline ( DiS-NH 2 ), p K a = 2.14 ± 0.09, and CB7·DiS-NH 2 , p K a = 3.26 ± 0.09), thus favoring applications in different kinds of crop soils. Kinetic studies have demonstrated the stability of the CB7·APO complex at different pH media for more than 90 min. An in vitro bioassay with etiolated wheat coleoptiles showed that the bioactivity of APO and DiS-NH 2 is enhanced upon complexation.

Herbicides play a vital role in agriculture, contributing to increased crop productivity by minimizing weed growth, but their low degradability presents a threat to the environment and human health. Allelochemicals, such as DIBOA (2,4-dihydroxy-(2H)-1,4-benzoxazin-3(4 H)-one), are secondary metabolites released by certain plants that affect the survival or growth of other organisms. Although these metabolites have an attractive potential for use as herbicides, their low natural production is a critical hurdle. Previously, the synthesis of the biologically active analog D-DIBOA (4-hydroxy-(2H)-1,4-benzoxazin-3(4H)-one) was achieved, using an engineered E. coli strain as a whole-cell biocatalyst, capable of transforming a precursor compound into D-DIBOA and exporting it into the culture medium, although it cannot be directly applied to crops. Here a chromatographic method to purify D-DIBOA from this cell culture medium without producing organic solvent wastes is described. The purification of D-DIBOA from a filtered culture medium to the pure compound could also be automated. Biological tests with the purified compound on weed models showed that it has virtually the same activity than the chemically synthesized D-DIBOA., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 The Authors. Published by Elsevier B.V. All rights reserved.)

Background: Natural products are a promising source for the development of new pesticides with alternative mechanisms of action. In this study, we evaluated the phytotoxic and antifungal activity of a novel family of natural C 17 -sesquiterpenoids and performed a study of the effect caused by the elimination of the α-methylene-γ-butyrolactone system and its importance to their biological activity., Results: Many tested compounds exhibited a strong phytotoxic activity. Lappalone and pertyolide B were the most potent molecules from the tested group. Lappalone displayed a strong inhibition profile against selected weed species, reaching a half-maximal inhibitory concentration (IC 50 ) value of 5.0 μm against Echinochloa crus-galli L. shoot and 5.7 μm against the germination rate of Amaranthus viridis L., as well as a good stimulation of the germination of Phelipanche ramosa L. Pertyolide B demonstrated excellent inhibition against Amaranthus viridis L. (IC 50 : 56.7, 70.3 and 24.0 μm against the root and shoot growth, and germination rate, respectively) and Allium cepa L. (representative of the Liliaceae family, with IC 50 values of 25.3 and 64.4 μm against root and shoot growth). Regarding the antifungal activity, pertyolide B presented significant activity against Colletotrichum fragareae and Fusarium oxysporum with a minimum inhibitory concentration of 6.6 μg μL -1 ., Conclusion: The bioassays revealed that frequently the presence of the α-methylene-γ-butyrolactone system is not essential for the bioactivities of sesquiterpene lactones, and suggest that C 17 -sesquiterpenoids may function through a different mechanism of action not related to the widely assumed Michael addition. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry., (© 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.)

In the work described here, a number of sesquiterpenes and benzoxazinoids from natural sources, along with their easily accessible derivatives, were evaluated against the main protease, RNA replicase and spike glycoprotein of SARS-CoV-2 by molecular docking. These natural products and their derivatives have previously shown remarkable antiviral activities. The most relevant compounds were the 4-fluoro derivatives of santamarine, reynosin and 2-amino-3 H -phenoxazin-3-one in terms of the docking score. Those compounds fulfill the Lipinski's rule, so they were selected for the analysis by molecular dynamics, and the kinetic stabilities of the complexes were assessed. The addition of the 4-fluorobenzoate fragment to the natural products enhances their potential against all of the proteins tested, and the complex stability after 50 ns validates the inhibition calculated. The derivatives prepared from reynosin and 2-amino-3 H -phenoxazin-3-one are able to generate more hydrogen bonds with the M pro , thus enhancing the stability of the protein-ligand and generating a long-term complex for inhibition. The 4-fluoro derivate of santamarine and reynosin shows to be really active against the spike protein, with the RMSD site fluctuation lower than 1.5 Å. Stabilization is mainly achieved by the hydrogen-bond interactions, and the stabilization is improved by the 4-fluorobenzoate fragment being added. Those compounds tested in silico reach as candidates from natural sources to fight this virus, and the results concluded that the addition of the 4-fluorobenzoate fragment to the natural products enhances their inhibition potential against the main protease, RNA replicase and spike protein of SARS-CoV-2.

The encapsulation of bioactive natural products has emerged as a relevant tool for modifying the poor physicochemical properties often exhibited by agrochemicals. In this regard, natural guaiane-type sesquiterpene lactones isolated from Cynara cardunculus L. have been encapsulated in a core/shell nanotube@agrochemical system. Monitoring of the F and O signals in marked sesquiterpenes confirmed that the compound is present in the nanotube cavity. These structures were characterized using scanning transmission electron microscopy-X-ray energy-dispersive spectrometry techniques, which revealed the spatial layout relationship and confirmed encapsulation of the sesquiterpene lactone derivative. In addition, biological studies were performed with aguerin B ( 1 ), cynaropicrin ( 2 ), and grosheimin ( 3 ) on the inhibition of germination, roots, and shoots in weeds ( Phalaris arundinacea L., Lolium perenne L., and Portulaca oleracea L.). Encapsulation of lactones in nanotubes gives better results than those for the nonencapsulated compounds, thereby reinforcing the application of fully organic nanotubes for the sustainable use of agrochemicals in the future.

Nitrogen (N) and phosphorus (P) are among the most important macronutrients for plant growth and development, and the most widely used as fertilizers. Understanding how plants sense and respond to N and P deficiency is essential to optimize and reduce the use of chemical fertilizers. Strigolactones (SLs) are phytohormones acting as modulators and sensors of plant responses to P deficiency. In the present work, we assess the potential role of SLs in N starvation and in the N-P signalling interplay. Physiological, transcriptional and metabolic responses were analysed in wild-type and SL-deficient tomato plants grown under different P and N regimes, and in plants treated with a short-term pulse of the synthetic SL analogue 2'-epi-GR24. The results evidence that plants prioritize N over P status by affecting SL biosynthesis. We also show that SLs modulate the expression of key regulatory genes of phosphate and nitrate signalling pathways, including the N-P integrators PHO2 and NIGT1/HHO. The results support a key role for SLs as sensors during early plant responses to both N and phosphate starvation and mediating the N-P signalling interplay, indicating that SLs are involved in more physiological processes than so far proposed., (© 2021 The Authors. Plant, Cell & Environment published by John Wiley & Sons Ltd.)

Introduction: Emotion recognition of voices may play an important role in interpersonal communication and patients with schizophrenia present alterations in this regard. Several on-line rehabilitation tools have been developed for treatment in this area. Voices is an on-line prosodic recognition program consisting of identifying different emotional tones in neutral phrases, in different sessions of gradually increasing difficulty. This training tool has previously reported benefits, and a new version has been created called Voices 2 . The main aim of this study is to test the capacity of the Voices 2 program to improve emotion recognition through prosody for adults with schizophrenia. Secondly, it seeks to observe durability effects 1 month after intervention. Method: A randomized, single-blind, multicenter clinical trial was conducted with 44 outpatients diagnosed with schizophrenia or schizoaffective disorder. The intervention group (also called Voices ) was treated with Voices 2 , whereas the control group was treated with auditory training that was not related to emotions. Sociodemographic and clinical data, clinical state (PANSS), Intelligence Quotient and prosodic recognition (RMV-SV) were measured at baseline. After intervention, RMV-SV and PANSS were assessed. One month later, the RMV-SV measure was repeated. Results: The control group ( n = 19) and the Voices group ( n = 22) did not differ on χ 2 , t or U tests in sociodemographic, clinical and psychometric variables at baseline or post-intervention (all p -values > 0.05). In the Voices group, statistically significant differences were observed in the RMV-SV scale applied post-intervention vs. that applied pre-intervention ( Z = 2.47, p = 0.013). Similar results were observed in the 1-month follow-up RMV-SV vs. the pre-intervention RMV-SV ( Z = 1.97, p = 0.049). PANSS scale was also assessed with no significant differences between pre vs. post measures in both groups. Lastly, Voices 2 was rated relatively higher, based on its ease of understanding, entertainment value, usefulness and the appropriateness of use of its emotional glossary. Discussion: Improvements were observed in prosodic recognition following intervention with Voices 2 in the Voices group. Although these results are similar to other clinical trial rehabilitation programs, specific research on the matter remains scarce. Certain aspects, such as the durability of effects or adherence should be thoroughly studied and clarified. Clinical Trial Registration: [https://doi.org/10.17605/OSF.IO/G95C4]., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Lado-Codesido, Rey Varela, Larios Quiñones, Martínez Agulleiro, Ossa Basanes, Martínez Querol, Mateos, Spuch and García-Caballero.)

C 17 -sesquiterpenoids are a group of natural products that have been recently discovered. These compounds have the peculiarity of lacking the α,β-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.

Piptocarpha rotundifolia (Less.) Baker stands out as one of the species with the highest frequency, density, and relative dominance in the Cerrado formations. However, no phytochemical studies have been carried out with this species to date. The aim of this study was to evaluate the phytotoxic activity of P. rotundifolia leaves in the search of new environmentally friendly tools for weed control. Thus, a wheat coleoptile and phytotoxic bioassay, using relevant agricultural weeds, was used to identify the most active extracts and fractions. The subsequent purification process allowed the isolation of 11 compounds, the phytotoxicity of which was evaluated in terms of wheat coleoptile elongation and with the most sensitive weeds. Piptocarphin A was found to be the major compound and the most active. To confirm its phytotoxic potential, the effect on Ipomea grandifolia grown in a hydroponic culture and on metaxylem cells was studied. The results obtained in this study demonstrate that the inhibitory activity displayed by P. rotundifolia leaf extract is mainly due to the presence of piptocarphin A. The phytotoxicity shown by P. rotundifolia leaf extract, and the isolated compounds, on weeds could provide new tools for weed control in agricultural fields.

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 ® ), 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.

Semisynthetic analogs of natural products provide an important approach to obtain safer and more active drugs and they can also have enhanced physicochemical properties such as persistence, cross-membrane processes and bioactivity. Acyl derivatives of different natural product families, from sesquiterpene lactones to benzoxazinoids, have been synthesized and tested in our laboratories. These compounds were evaluated against tumoral and nontumoral cell lines to identify selective derivatives with a reduced negative impact upon application. The mode of action of these compounds was analyzed by anti-caspase-3 assays and molecular dynamics simulations with cell membrane re-creation were also carried out. Aryl derivatives of eudesmanolide stand out from the other compounds and are better than current anticancer drugs such as etoposide in terms of selectivity and activity. Computational studies provide evidence that lipophilicity plays a key role and the 4-fluorobenzoyl derivative can pass easily through the cell membrane., (© 2020 Wiley-VCH GmbH.)

Application of natural products as new green agrochemicals with low average lifetime, low concentration doses, and safety is both complex and expensive due to chemical modification required to obtain desirable physicochemical properties. Transport, aqueous solubility, and bioavailability are some of the properties that have been improved using functionalized metal-organic frameworks based on zinc for the encapsulation of bioherbicides ( ortho -disulfides). An in situ method has been applied to achieve encapsulation, which, in turn, led to an improvement in water solubility by more than 8 times after 2-hydroxypropyl-β-cyclodextrin HP-β-CD surface functionalization. High-resolution high-angle annular dark-field scanning transmission electron microscopy (HR HAADF-STEM) and integrated differential phase contrast (iDPC) imaging techniques were employed to verify the success of the encapsulation procedure and crystallinity of the sample. Inhibition studies on principal weeds that infect rice, corn, and potato crops gave results that exceed those obtained with the commercial herbicide Logran. This finding, along with a short synthesis period, i . e ., 2 h at 25 °C, make the product an example of a new generation of natural-product-based herbicides with direct applications in agriculture.

The work described here follows on from a previous study focused on the influence of the genotype and harvest time on the sesquiterpene lactone (STL) profile of Cynara cardunculus L. leaf extracts. The aim of this study was to investigate the effect that 60% plant shading in cultivated cardoon ( C. cardunculus var. altilis ) leaf extracts harvested in winter and spring had on the composition of STLs and the phytotoxicity. The phytotoxicity of leaf extracts was evaluated by assessing wheat coleoptile elongation along with seed germination and the root and shoot length of the weeds Amaranthus retroflexus L. and Portulaca oleracea L. Shading increased the production of STLs in spring, and this effect correlated positively with the phytotoxic activity. The induction of shading can therefore be used to modulate STL concentrations and their phytotoxic potential in cultivated cardoon leaves for industrial applications.

Strigolactones are natural products that are exuded by plants and stimulate parasitic weed germination. Their use in herbicides is limited since they are produced in small quantities, but the synthesis of bioactive analogues provides an alternative source. In this work, eleven analogues have been synthesized. Among them, nine compounds belong to a novel family named eudesmanestrigolactones. The procedure is short (3-6 steps), the starting materials are isolated on a multigram scale, and global yields are up to 8%, which significantly enhance isolated yields. In bioassay, the compounds germinated high percentages of Phelipanche ramosa , Orobanche cumana , and Orobanche crenata seeds, even at nanogram doses (100 nM). Bioactivity was stereochemistry-dependent, and it was discussed in terms of the presence and geometry of the enol ether, orientation of the butenolide, and unsaturation of ring A. The reported compounds provide a set of readily obtained allelochemicals with potential applications as preventive herbicides.

Weeds have been a major threat in agriculture for several generations as they lead to decreases in productivity and cause significant economic losses. Parasitic plants are a specific type of weed causing losses in crops of great relevance. A new strategy has emerged in the fight against parasitic plants, which is called 'suicidal germination' or the 'honey-pot strategy'. Regarding the problem of weed control from an ecological point of view, it is interesting to investigate new natural compounds with allelopathic activity with the aim of developing new natural herbicides that can inhibit the growth of weeds without damaging the environment. Safflower crops have been affected by parasitic plants and weeds and, as a consequence, the secondary metabolites exuded by safflower roots have been studied. The sesquiterpene lactone dehydrocostuslactone was isolated and characterised, and the structurally related costunolide was identified by UHPLC-MS/MS in safflower root exudates. These sesquiterpene lactones have been shown to stimulate germination of Phelipanche ramosa and Orobanche cumana seeds. In addition, these compounds were phytotoxic on three important weeds in agriculture, namely Lolium perenne, Lolium rigidum and Echinochloa crus-galli. The exudation of the strigolactones solanacol and fabacyl acetate have also been confirmed by UHPLC-MS/MS. The study reported here contributes to our knowledge of the ecological role played by some secondary metabolites. Moreover, this knowledge could help identify new models for the development of future agrochemicals based on natural products.

Strigolactones (SLs) are important ex-planta signalling molecules in the rhizosphere, promoting the association with beneficial microorganisms, but also affecting plant interactions with harmful organisms. They are also plant hormones in-planta, acting as modulators of plant responses under nutrient-deficient conditions, mainly phosphate (Pi) starvation. In the present work, we investigate the potential role of SLs as regulators of early Pi starvation signalling in plants. A short-term pulse of the synthetic SL analogue 2'-epi-GR24 promoted SL accumulation and the expression of Pi starvation markers in tomato and wheat under Pi deprivation. 2'-epi-GR24 application also increased SL production and the expression of Pi starvation markers under normal Pi conditions, being its effect dependent on the endogenous SL levels. Remarkably, 2'-epi-GR24 also impacted the root metabolic profile under these conditions, promoting the levels of metabolites associated to plant responses to Pi limitation, thus partially mimicking the pattern observed under Pi deprivation. The results suggest an endogenous role for SLs as Pi starvation signals. In agreement with this idea, SL-deficient plants were less sensitive to this stress. Based on the results, we propose that SLs may act as early modulators of plant responses to P starvation., (© 2020 John Wiley & Sons Ltd.)

Herbicides are a key element in agriculture but they do cause environmental problems and natural alternatives are being sought. In this context, invasive plants could provide an as yet unexplored source for the development of future herbicides. Urochloa humidicola has great invasive potential in Brazilian environments as it hampers the establishment of other plants. The phytotoxicity of U. humidicola root extracts has been evaluated, and the major components have been identified. The phytotoxicity of the extract was assessed in the wheat coleoptile assay on seeds of troublesome weeds and on Anadenanthera colubrina , a tree species used in ecological restoration programs. The ethyl acetate extract showed the highest activity, and the most affected weeds were E. crus-galli , M. maximus , and A. viridis with the latter weed more affected by the extract than by the herbicide Logran. Microscopic ultrastructural analysis of A. colubrina roots indicated possible signals of cell death. Seven compounds were identified in the ethyl acetate extract of which one diterpene and four saponins are new. Six of these compounds were tested in the wheat coleoptile bioassay. The most active were diterpene 1 and saponins 2 , 3 , and 6 . The phytotoxic activity of U. humidicola explains the issues observed in ecological restoration with A. colubrina in the presence of Urochloa species, and its effect on weeds reinforces its potential use in agriculture.

Strigolactones (SLs) are a family of natural products produced by the plants as shoot branching factors and responsible for the induction of hyphal branching in arbuscular mycorrhizal (AM) fungi. They have been also used by parasitic plant seeds as stimulators of their germination as a strategy to ensure the presence of a host in the environment. For all these bioactivities, SLs have kept the attention of the researchers in the last years, increasing the number of published papers, and have opened new areas of research in the multiple roles that they play in the rhizosphere and as plant hormones. However, the low amount of them produced by plants and their rapid degradability make it crucial to develop fast analytical methods with very low limits of quantification. Herein, it is described a protocol for the development of an LC-MS/MS method for the quantification of SLs, using GR24 as IS, in roots exudates and extracts.

Agrochemical encapsulation agents used up to now are commonly based on polymeric compounds or metal particles, but the employment of other natural products such as host structures has not been tackled in detail. In the work reported here, fully organic nanotubes composed of human bile acid (lithocholic acid) have been synthesized. These nanotubes were employed to encapsulate potential disulfide herbicide mimics that have previously shown relevant inhibitory activity against weeds. The three-dimensional chemical information from scanning transmission electron microscope analytical tomography with subnanometer scale resolution convincingly demonstrates for the first time the occurrence of efficient encapsulation within a fully organic nanotube of different organic molecules with activity as herbicides. The encapsulation was achieved in a one-pot synthesis, in an aqueous environment and under in situ conditions without using any marker or coating with contrast materials, which renders the process greener than those routinely used. The nanotubes allow complete water solubilization, with an encapsulation percentage of up to 78% in all of the herbicide compounds. Furthermore, nanotubes showed a flattened arrangement due to the host-guest interaction. The synthetic approach represents a step forward in solving the key problem of the quite limited solubility of natural agrochemicals in aqueous environments. In addition, the process presents a breakthrough in the use of natural products produced by the human body as encapsulating agents, which expands possible future applications. The preliminary docking approach clarifies that the 2o01 transmembrane transport protein seems to be the prior channel of the organic nanotube in the delivery process to vegetable cells. The etiolated wheat coleoptile bioassay demonstrated that the encapsulated herbicides have improved the bioactivity of free compounds, keeping 60% of inhibition of the weed at least for every disulfide, a requisite for their fruitful application as agrochemicals.

Inorganic phosphorus (Pi) fertilizers are expected to become scarce in the near future; so, breeding for improved Pi acquisition-related root traits would decrease the need for fertilizer application. This work aimed to decipher the physiological and molecular mechanisms underlying the differences between two commercial wheat cultivars (Crac and Tukan) with contrasting Pi acquisition efficiencies (PAE). For that, four independent experiments with different growth conditions were conducted. When grown under non-limiting Pi conditions, both cultivars performed similarly. Crac was less affected by Pi starvation than Tukan, presenting higher biomass production, and an enhanced root development, root:shoot ratio, and root efficiency for Pi uptake under this condition. Higher PAE in Crac correlated with enhanced expression of the Pi transporter genes TaPht1;2 and TaPht1;10. Crac also presented a faster and higher modulation of the IPS1-miR399-PHO2 pathway upon Pi starvation. Interestingly, Crac showed increased levels of strigolactones, suggesting a direct relationship between this phytohormone and plant P responses. Based on these findings, we propose that higher PAE of the cultivar Crac is associated with an improved P signalling through a fine-tuning modulation of PHO2 activity, which seems to be regulated by strigolactones. This knowledge will help to develop new strategies for improved plant performance under P stress conditions., (© The Author(s) 2019. Published by Oxford University Press on behalf of the Society for Experimental Biology.)

The alkaloid ricinine (3-cyano-4-methoxy-N-methyl-2-pyridone) is found in different parts of the Ricinus communis plant and is known to possess several bioactive properties, including strong antioxidant activity. In this study, a new microwave-assisted extraction (MAE) method was developed for the recovery of ricinine from R. communis leaves. The extraction variables studied were extraction temperature (between 125 °C and 175 °C), microwave power (between 500 W and 1000 W), extraction time (between 5 min and 15 min), extraction solvent (between 10% and 90% of EtOAc in MeOH), and solvent-to-sample ratio (between 25:1 mL and 50:1 mL of solvent per gram of the sample). On studying the effects of extraction variables, both solvent and liquid-to-solid ratio were found to exhibit the highest effects on ricinine recovery. A fast (15 min) microwave-assisted extraction method was developed (high temperatures can be applied because the stability of ricinine is proven in the literature), allowing for the recovery of ricinine from R. communis leaves. The study revealed that R. communis leaves had almost 1.5 mg g -1 (dried weight) of ricinine.

11,13-Dehydro seco -guaianolides, a particular type of sesquiterpene lactones, were synthesized from the commercially available α-santonin ( 11 ) using a facile strategy involving a high-yielding photochemical reaction. Natural products 10 and 17 from Artemisia gorgonum were synthesized in good yields. Specifically, compound 10 was obtained in five steps with an overall yield of 17%. The sesquiterpene lactones were tested in the etiolated wheat coleoptile bioassay, and the most active compounds were assayed on standard target species. Guaianolide 13 showed the highest phytotoxic activities when compared with the known herbicide Logran.

It has been hypothesized that the α-methylene-γ-lactone moiety of sesquiterpene lactones is a key unit for their bioactivity. As a consequence, modifications of these compounds have been focused on this fragment. In the work reported here, two sesquiterpene lactones, namely, dehydrocostuslactone and β-cyclocostunolide, a eudesmanolide obtained by controlled cyclization of costunolide, were chosen for modification by Michael addition at C-13. On applying this reaction to both compounds, it was possible to introduce the functional groups alkoxy, amino, carbamoyl, hydroxy, and thiol to give products in good to high yields, depending on the base and solvent employed. In particular, the introduction of a thiol group at C-13 in both compounds was achieved with outstanding yields (>90%) and this is unprecedented for these sesquiterpene lactones. The bioactivities of the products were evaluated on etiolated wheat coleoptile elongation and germination of seeds of parasitic weeds, with significant activity observed on Orobanche cumana and Phelipanche ramosa . The structure-activity relationships are discussed.

The excessive and inappropriate application of herbicides has caused environmental pollution. The use of allelochemicals as bioherbicides could provide a solution to this problem. The allelopathic activity of Cynara cardunculus L. has been studied previously, and sesquiterpene lactones (STLs) were identified as the most relevant allelochemicals. The goal of the study reported here was to investigate the effect of six genotypes and three harvest times on the qualitative and quantitative composition of STLs in C. cardunculus leaves through a new ultra-high-performance liquid chromatography-tandem mass spectrometry analysis method and, thus, the effect on phytotoxicity. Overall, wild cardoon contained the highest levels of STLs of the three botanical varieties studied. Nevertheless, climatic conditions had a marked influence on the presence of STLs among the six genotypes, which was higher in the April harvest. Cynaropicrin was the most abundant STL detected. A close relationship was found between the STL profiles and the allelopathic activity, expressed as inhibition of wheat coleoptile elongation. The data provide a new and important contribution to our understanding of C. cardunculus allelopathy.

The excessive proliferation of toxin producing cyanobacteria constitutes a significant health risk to the environment and humans. This is due to the contamination of potable water and accumulation of cyanotoxins in plant and animal tissues. As a means of controlling bloom forming cyanobacteria, secondary metabolites with pro-oxidative activities from plants are used to treat water bodies contaminated with cyanobacterial blooms and their associated toxins. The objective of the present study was to evaluate the mechanism of action of extract, fractions and isolated flavonoids of Tridax procumbens L. on Microcystis aeruginosa (Kützing) Kützing. by monitoring changes in growth, oxidative stress, antioxidant response, and cyanatoxin microcystins (MCs) production. The extract, fraction 3 and the isolated flavonoids significantly reduced the cell density of the cyanobacterium. Furthermore, the extract and fraction 3 increased the production of reactive oxygen species, induced lipid peroxidation, and altered antioxidant enzyme activities of M. aeruginosa. The total MCs content of the cyanobacterium was negatively affected by the presence of the extract, fractions and isolated flavonoids. The present study show that T. procumbens has secondary metabolites that are capable of interfering with the physiology and microcystins production of M. aeruginosa. These characteristics are promising for the control of this noxious cyanobacterium in aquatic ecosystems., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Crocus sativus stigmas are the main source of crocins, which are glucosylated apocarotenoids derived from zeaxanthin cleavage that give saffron its red color. Phytoene synthase (PSY) mediates the first committed step in carotenoid biosynthesis in plants. Four PSY genes encoding functional enzymes were isolated from saffron. All the proteins were localized in plastids, but the expression patterns of each gene, CsPSY1a , CsPSY1b , CsPSY2 , and CsPSY3 , in different saffron tissues and during the development of the stigma showed different tissue specialization. The CsPSY2 transcript was primarily detected in the stigmas where it activates and stimulates the accumulation of crocins, while its expression was very low in other tissues. In contrast, CsPSY1a and CsPSY1b were mainly expressed in the leaves, but only CsPSY1b showed stress-light regulation. Interestingly, CsPSY1b showed differential expression of two alternative splice variants, which differ in the intron retention at their 5' UTRs, resulting in a reduction in their expression levels. In addition, the CsPSY1a and CsPSY1b transcripts, together with the CsPSY3 transcript, were induced in roots under different stress conditions. The CsPSY3 expression was high in the root tip, and its expression was associated with mycorrhizal colonization and strigolactone production. CsPSY3 formed a separate branch to the stress-specific Poaceae homologs but was closely related to the dicot PSY3 enzymes.

A bio-guided study of leaf extracts allowed the isolation of two new macrobicyclic hydrolysable tannins, namely merianin A ( 1 ) and merianin B ( 2 ), and oct-1-en-3-yl β -xylopyranosyl-(1"-6')- β -glucopyranoside ( 3 ) from Meriania hernandoi , in addition to 11 known compounds reported for the first time in the Meriania genus. The structures were elucidated by spectroscopic analyses including one- and two-dimensional NMR techniques and mass spectrometry. The bioactivities of the compounds were determined by measuring the DPPH radical scavenging activity and by carrying out antioxidant power assays (FRAP), etiolated wheat coleoptile assays and phytotoxicity assays on the standard target species Lycopersicum esculentum W. (tomato). Compounds 1 and 2 exhibited the best free radical scavenging activities, with FRS 50 values of 2.0 and 1.9 µM, respectively.

Introduction: Strigolactones (SLs) are the most representative germination stimulants for seeds of root parasitic plants, and they show activity even at concentrations below 10 -10  M. The low amounts of stimulants produced by the host and their rapid degradability make it crucial to develop analytical methods with very low limits of quantification., Objective: To develop a sensitive and validated analytical method for the simultaneous quantification of seven SLs [7-oxoorobanchyl acetate (1), solanacol (2), orobanchol (4), strigol (5), fabacyl acetate (6), orobanchyl acetate (7), and 5-deoxystrigol (8)]., Methods: SLs were analysed using ultra-high performance liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS), with (±)-GR24 (3) employed as internal standard (IS). Validation was based on selectivity, linearity, precision of the peak areas (repeatability and intermediate precision), detection and quantification limits, and stability., Results: A simple, rapid and reliable UHPLC-MS/MS method has been validated for the routine analysis of seven SLs and has been successfully applied to quantify them in exudates and extracts from tomato roots (Solanum lycopersicum). The limits of quantifications range from 0.05 μg/L for 5-deoxystrigol to 0.96 μg/L for solanacol., Conclusion: The method provides a useful tool for research in all the fields related to SLs, both for studies related to their function as hormones, and signalling molecules in the rhizosphere, without sample preparation required for extracts and root exudates in less than 11 minutes., (© 2018 John Wiley & Sons, Ltd.)

Stigmasterol, bergapten, and α-tomatine were isolated from tomato roots. The preliminary phytotoxic activities of stigmasterol and α-tomatine were evaluated in a wheat-coleoptile bioassay, and α-tomatine was more active than stigmasterol. To confirm its phytotoxic activity, α-tomatine was tested on Lactuca sativa and two weeds ( Lolium perenne and Echinochloa crus-galli), and it was active in all cases. The stimulatory activities of α-tomatine and stigmasterol on parasitic-plant germination were also evaluated, and α-tomatine was found to be active on Phelipanche ramosa, a parasitic plant of tomato. α-Tomatine was identified in root exudates by LC-MS/MS. This confirms that α-tomatine is exuded by roots into the environment, where it could act as both an allelochemical and a stimulator of P. ramosa, a parasitic plant of tomato.

Background: Soybean (Glycine max) is an important oleaginous legume that has been cultivated in new areas in Brazil, including pastures. Problems of reduced production yields have been reported by soybean growers when the crop is sown immediately after desiccation of pastures of Urochloa spp. using glyphosate. The objective of this work was to extract, isolate and identify the major chemicals from U. ruziziensis that have phytotoxic activity and to evaluate the possible relation between this effect and reduced soybean yield., Results: U. ruziziensis plants at the flowering stage were desiccated using glyphosate at 1.44 kg ha -1 . The plants were collected between five and ten days after treatment. Extracts of dried and ground shoots were obtained by sequential extraction with hexane, dichloromethane and methanol. The results of wheat coleoptile bioassays indicated that the methanol extract was more inhibitory than the dichloromethane extract regardless of glyphosate application., Conclusion: Protodioscin, a steroidal saponin, was isolated from the extract as the major component and the activities of this compound were in good agreement with those found for the extract. The release of this compound into the soil is a plausible explanation for the decrease in production observed in transgenic soybean crop after desiccation of U. ruziziensis. © 2017 Society of Chemical Industry., (© 2017 Society of Chemical Industry.)

Isohexenylnaphthazarins are commonly found in the root periderm of several Boraginaceous plants and are known for their broad range of biological activities. The work described herein concerns the biological activity of compounds from the roots of Echium plantagineum L. and Echium gaditanum Boiss (Boraginaceae) collected from field sites in southern Spain and Australia. Bioactivity was assessed using etiolated wheat coleoptile bioassay and in vitro growth inhibitory activity in HeLa and IGROV-1 cells. The quantification of four isohexenylnaphthazarins (shikonin/alkannin, deoxyshikonin/deoxyalkannin, acetylshikonin/acetylalkannin and dimethylacrylshikonin/dimethylacrylalkannin) was performed by LC-MS/MS using juglone as internal standard. Correlation coefficient values for the activities and concentrations of these four analytes were in the linear range and were greater than 0.99. Acetylshikonin/acetylalkannin and dimethylacrylshikonin/dimethylacrylalkannin were present in the highest concentrations in extracts of both species. The results reveal that greatest overall inhibition was observed in both bioassays with E. gaditanum extracts. Strong correlations between time of collection, sampling location and bioactivity were identified., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Farmers of the Franca region in Brazil observed that Bidens sulphurea was able to eliminate the Panicum maximum weed, which infected coffee plantations, without affecting the crop. In an effort to determine if the inhibitory effects observed were due to the presence of phytotoxic compounds from leaves and roots, a biodirected isolation and spectroscopic characterization has been carried out. The leaf dichloromethane and root acetone extracts were the most active, and the former appeared to be more phytotoxic to the target species, including four weeds. A total of 26 compounds were isolated from leaves and roots, and four of them are described here for the first time. The major compounds in the leaf extract are the sesquiterpene lactones costunolide, reynosin, and santamarine, and these showed marked inhibition. Amaranthus viridis and Panicum maximum were the most sensitive species of the weeds tested. These three phytotoxic lactones were also evaluated on A. viridis and P. maximum under hydroponic conditions. A. viridis was the most affected species with the three lactones, and santamarine was the most phytotoxic compound on both. This is the first time that the phytotoxicity of sesquiterpene lactones has been evaluated on hydroponic culture. The work described here is a preliminary approach for the use of B. sulphurea for weed control in agriculture, both as a cover crop and by use of its components as natural herbicide leads.

The work described herein is a continuation of a previous study centered on the bioprospect of cardoon (Cynara cardunculus) leaf extracts through the isolation of secondary metabolites with phytotoxic activity. Chromatographic fractionations of the ethyl acetate extract and spectroscopic analysis showed that the majority of the components were sesquiterpene lactones. Of these compounds, aguerin B, grosheimin, and cynaropicrin were very active on etiolated wheat coleoptile, standard target species, and weed growth. The joint action of binary mixtures of these three active sesquiterpene lactones and one nonactive compound (11,13-dihydroxy-8-desoxygrosheimin) was studied. The activities of fixed-ratio mixtures were assessed on wheat coleoptile. The results can be interpreted with respect to a reference model by considering dose-response analyses and isobolograms with linear regression analyses. A total of 17 binary mixtures at different levels of inhibition (ED25, ED50, and ED75) were studied, and predominantly they responded additively (25). Deviations from additivity included seven synergistic responses and two antagonistic responses. The joint action of major sesquiterpene lactones isolated from C. cardunculus can explain the activities observed in extracts and fractions. The results reported here reiterate the utility of the wheat coleoptile bioassay as a quick tool to detect potential synergistic effects in binary mixtures.

The neotropical bracken fern Pteridium arachnoideum (Kaulf.) Maxon. (Dennstaedtiaceae) is described as an aggressive pioneer plant species. It invades abandoned or newly burned areas and represents a management challenge at these invaded sites. Native to the Atlantic Forest and Cerrado (Tropical Savanna) Brazilian biomes, P. arachnoideum has nevertheless become very problematic in these conservation hotspots. Despite some reports suggesting a possible role of allelopathy in this plant's dominance, until now there has been little evidence of isolated and individually identified compounds with phytotoxic activities present in its tissues or in the surrounding environment. Thus, the aim of this study was to investigate the allelopathic potential of P. arachnoideum by isolating and identifying any secondary metabolites with phytotoxic activity in its tissues, litter, and soil. Bioguided phytochemical investigation led to the isolation and identification of the proanthocyanidin selligueain A as the major secondary compound in the green fronds and litter of this fern. It is produced by P. arachnoideum in its green fronds, remains unaltered during the senescence process, and is the major secondary compound present in litter. Selligueain A showed phytotoxic activity against the selected target species sesame (Sesamum indicum) early development. In particular, the compound inhibited root and stem growth, and root metaxylem cell size but did not affect chlorophyll content. This compound can be considered as an allelochemical because it is present in the soil under P. arachnoideum patches as one of the major compounds in the soil solution. This is the first report of the presence of selligueain A in any member of the Dennstaedtiaceae family and the first time an isolated and identified allelochemical produced by members of the Pteridium species complex has been described. This evidence of selligueain A as a putative allelochemical of P. arachnoideum reinforces the role of allelopathy in the dominance processes of this plant in the areas where it occurs., Competing Interests: The authors have declared that no competing interests exist.

Despite the increase in recent decades in herbicide research on the potential of native plants, current knowledge is considered to be low. Very few studies have been carried out on the chemical profile or the biological activity of the Brazilian savanna (Cerrado) species. In the study reported here, the allelopathic activity of AcOEt and MeOH extracts of leaves, stems, and roots from Ocotea pulchella Nees was evaluated. The extracts were assayed on etiolated wheat coleoptiles. The AcOEt leaf extract was the most active and this was tested on standard target species (STS). Lycopersicon esculentum and Lactuca sativa were the most sensitive species in this test. A total of eleven compounds have been isolated and characterized. Compounds 1, 2, 4, and 6 have not been identified previously from O. pulchella and ocoteol (9) is reported for the first time in the literature. Eight compounds were tested on wheat coleoptile growth, and spathulenol, benzyl salicylate, and benzyl benzoate showed the highest activities. These compounds showed inhibitory activity on L. esculentum. The values obtained correspond to the activity exhibited by the extract and these compounds may therefore be responsible for the allelopathic activity shown by O. pulchella., (© 2016 Wiley-VHCA AG, Zürich.)

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.

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.

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.

Limonoids and triterpenes are the largest groups of secondary metabolites and have notable biological activities. Meliaceae and Rutaceae are known for their high diversity of metabolites, including limonoids, and are distinguished from other families due to the frequent occurrence of such compounds. The increased interest in crop protection associated with the diverse bioactivity of these compounds has made these families attractive in the search for new allelopathic compounds. In the study reported here we evaluated the bioactivity profiles of four triterpenes (1-4) and six limonoids (5-10) from Meliaceae and Rutaceae. The compounds were assessed in a wheat coleoptile bioassay and those that had the highest activities were tested on the standard target species Lepidinum sativum (cress), Lactuca sativa (lettuce), Lycopersicon esculentum (tomato) and Allium cepa (onion). Limonoids showed phytotoxic activity and 5α,6β,8α, 12α- tetrahydro-28-norisotoonafolin (10) and gedunin (5) were the most active, with bioactivity levels similar to, and in some cases better than, those of the commercial herbicide Logran. The results indicate that these products could also be allelochemicals involved in the ecological interactions of these plant species.

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 β-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., (Copyright © 2014 Verlag Helvetica Chimica Acta AG, Zürich.)

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 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., (Copyright © 2014 Elsevier B.V. All rights reserved.)