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ABSTRACT: A b s t r a c t: The aim of this study was to assess the phytotoxic potential of leaves of Myrcia tomentosa, as well as to isolate and identify the main bioactive compounds. The results for the coleoptile and phytotoxicity bioassays indicated the ethyl acetate extract for the phyto-chemistry study, owing to the high activity and the maintenance of the activity at lower concentrations. This extract was chromatographed and subjected to 1 H NMR and 13 C NMR. Two major active compounds were isolated from the ethyl acetate extract of leaves of M. tomentosa: avicularin and juglanin. The fractions where these compounds were isolated showed potent inhibition of coleoptile growth. This paper is the first report on the pres-ence of the flavonoids avicularin and juglanin in species of Myrtaceae from Neotropical savanna and provides a basis for future studies on the bioprospecting of M. tomentosa.
Biochemical Systematics and Ecology 02/2013; 46:29-35. · 0.93 Impact Factor
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ABSTRACT: Commercially available santonin was used to synthesize seven sesquiterpene lactones using a facile strategy that involved a high-yielding photochemical reaction. Three natural products from Artemisia gorgonum were synthesized in good yields, and in the case of two compounds, absolute configurations were determined from X-ray quality crystals. The structures previously reported for these compounds were revised. Sesquiterpene lactones were tested using the etiolated wheat coleoptile bioassay, and the most active compounds were assayed in standard target species. seco-Guaianolide (4) showed higher phytotoxic activities than the known herbicide Logran. This high activity could be due to the presence of a cyclopentenedione ring. These results suggest that compound 4 should be involved in defense of A. gorgorum, displaying a wide range of activities that allow proposing them as new leads for development of a natural herbicide model with a seco-guaianolide skeleton.
Journal of Natural Products 11/2012; · 3.13 Impact Factor
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ABSTRACT: 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.
Bioorganic & medicinal chemistry 09/2012; 20(22):6662-8. · 2.82 Impact Factor
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ABSTRACT: The development of new bioactive molecules with potential application in pharmacology and agriculture by using natural products
as templates has been a widely used approach in the recent years. Focusing our attention in phytochemicals with potential
application in agriculture, allelochemicals (natural plant toxins) have been deeply researched with the main purpose of finding
phytotoxic substances to use as new herbicidal templates. The development of new analytical methodologies, improved bioassay
techniques and a complete understanding of the allelopathic phenomenon will provide new tools for natural herbicide models
development, in the context of the new approaches to integrated pest management. A deeper knowledge of the release and assimilation
of allelochemicals, and the degradation phenomena associated to them will aid to discover new chemical structures with potential
utility, in addition to a better understanding on the ecological interactions mediated by phytochemicals. The research on
these topics, made with promising allelochemicals such as benzoxazinones and their degradation derivatives, the improvements
on analytical design, the degradation mechanisms elucidation and the novel bioassay techniques recently developed, are revised
herein.
Phytochemistry Reviews 04/2012; 7(1):179-194. · 4.33 Impact Factor
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ABSTRACT: Two new quinones, (an isoprenoid quinone, and a dimeric anthraquinone) named naphthotectone and anthratectone, respectively, were isolated from bioactive leaf extracts from Tectona grandis. Their structures were determined by a combination of 1D and 2D NMR techniques. The bioactivity profile of naphthotectone was assessed using the etiolated wheat coleoptiles bioassay in aqueous solutions at concentrations ranging from 10(-3) to 10(-5)M, as well as the standard target species lettuce, cress, tomato, and onion. Naphthotectone showed high level of activities in both bioassays. This fact, along with the presence of this compound as the major component in Tectona grandis, suggests that it may be involved in the allelopathic activity previously described for this species, and probably in other defense mechanisms.
Journal of Chemical Ecology 12/2011; 37(12):1341-8. · 2.66 Impact Factor
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ABSTRACT: Benzoxazinones and their degradation compounds inhibited root growth and alpha-amylase activity in cress seedlings. The inhibitory activity of these compounds was divided into three groups: the high active group; 2,4-dihydroxy-7-methoxy-(2H)-1,4-benzoxazin-3(4H)-one, 2,4-dihydroxy-(2H)-1,4-benzoxazin-3(4H)-one, 4-hydroxy-7-methoxy-(2H)-1,4-benzoxazin-3(4H)-one, 4-hydroxy-(2H)-1,4-benzoxazin-3(4H)-one, the moderate active group; 7-methoxy-(2H)-1,4-benzoxazin-3(4H)-one, (2H)-1,4-benzoxazin-3(4H)-one, 6-methoxy-benzoxazolin-2(3H)-one, benzoxazolin-2(3H)-one and 2-amino-phenoxazine-3-one, and the low active group; 2-hydroxy-(2H)-1,4-benzoxazin-3(4H)-one, 2-hydroxy-7-methoxy-(2H)-1,4-benzoxazin-3(4H)-one, 2-amino-7-hydroxyphenoxazine-3-one and 2-amino-7-methoxyphenoxazine-3-one. The structure-activity of these compounds suggests that compounds that have benzoxazinone skeletons are the most active structure, and a hydroxyl group at position C-2 on the benzoxazinone skeleton may not affect inhibitory activity, whereas a hydroxyl group at position N-4 on the skeleton is essential for inhibitory activity. However, the concentration-response curves of these compounds and the I(50) values (the concentrations required for 50% inhibition) for root growth and alpha-amylase indicated that root growth was positively correlated with the alpha-amylase activity in the seedlings. alpha-Amylase is required not only for seed germination, but also subsequent seedling growth until photosynthesis is sufficient to support seedling growth. Therefore, these results suggest that the compounds studied here may inhibit the root growth of cress seedlings by inhibiting alpha-amylase activity.
Journal of plant physiology 10/2010; 167(15):1221-5. · 2.50 Impact Factor
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ABSTRACT: Fifteen novel derivatives of D-DIBOA, including aromatic ring modifications and the addition of side chains in positions C-2 and N-4, had previously been synthesised and their phytotoxicity on standard target species (STS) evaluated. This strategy combined steric, electronic, solubility and lipophilicity requirements to achieve the maximum phytotoxic activity. An evaluation of the bioactivity of these compounds on the systems Oryza sativa-Echinochloa crus-galli and Triticum aestivum-Avena fatua is reported here.
All compounds showed inhibition profiles on the two species Echinochloa crus-galli (L.) Beauv. and Avena fatua L. The most marked effects were caused by 6F-4Pr-D-DIBOA, 6F-4Val-D-DIBOA, 6Cl-4Pr-D-DIBOA and 6Cl-4Val-D-DIBOA. The IC(50) values for the systems Echinochloa crus-galli-Oryza sativa and Avena fatua-Triticum aestivum for all compounds were compared. The compound that showed the greatest selectivity for the system Echinochloa crus-galli-Oryza sativa was 8Cl-4Pr-D-DIBOA, which was 15 times more selective than the commercial herbicide propanil (Cotanil-35). With regard to the system Avena fatua-Triticum aestivum, the compounds that showed the highest selectivities were 8Cl-4Val-D-DIBOA and 6F-4Pr-D-DIBOA. The results obtained for 6F-4Pr-D-DIBOA are of great interest because of the high phytotoxicity to Avena fatua (IC(50) = 6 µM, r(2) = 0.9616).
The in vitro phytotoxicity profiles and selectivities shown by the compounds described here make them candidates for higher-level studies. 8Cl-4Pr-D-DIBOA for the system Echinochloa crus-galli-Oryza sativa and 6F-4Pr-D-DIBOA for Avena fatua-Triticum aestivum were the most interesting compounds.
Pest Management Science 10/2010; 66(10):1137-47. · 2.25 Impact Factor
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ABSTRACT: A series of apocarotenoids (1-8) and one carotenoid (9) were isolated from the leaves of Withania aristata. In addition, the tetraacetylated apocarotenoid glucosides 10-12 were obtained by acetylation, with derivative 9-hydroxymegastigma-4,6E-dien-3-one 9-O-beta-D-glucopyranoside tetraacetate (10) being described for the first time. The structures have been determined by spectroscopic and spectrometric means, mainly NMR and ESI-MS, and comparison with data reported in the literature. These metabolites were evaluated on a systematic phytotoxicity assay using the etiolated wheat coleoptile bioassay. Compounds 1-3, 9 and 12 were further assayed for their phytotoxicity on the target species Lepidium sativum, Lactuca sativa, Lycopersicum esculentum and Allium cepa. Among the assayed compounds, lutein (9) showed the most significant values for phytotoxicity, followed by the non-glycosylated apocarotenoids (6S, 9R)-vomifoliol (1) and 9-hydroxymegastigma-4,6E-dien-3-one (2).
Natural product communications 07/2010; 5(7):1043-7. · 1.24 Impact Factor
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ABSTRACT: We describe a synthetic approach for two families of compounds, the capsaicinoids and capsinoids, as part of a study of the quantitative relationship between structure and activity. A total of 14 capsaicinoids of increasing lateral chain lengths, from 2 to 16 carbon atoms, were synthesized. In addition, 14 capsinoids with identical lateral chains, as well as capsiate and dihydrocapsiate, have been synthesized, and a new method for the synthesis of these compounds has been developed. The yields range from 48.35 to 98.98%. It has been found that the synthetic capsaicinoids and capsinoids present a lipophilia similar to those of the natural compounds and present similar biological activity. The bioactivity of the synthetic capsaicinoids and capsinoids decreases proportionally to the degree of difference in lipophilia (higher or lower) compared to the natural compounds. Biological activity was determined using the etiolated wheat (Triticum aestivum L.) coleoptiles bioassay and by comparing results of the synthesis with those presented by their counterpart natural compounds. The bioactivities found correlated directly to the lipophilic properties of the synthesized compounds.
Journal of Agricultural and Food Chemistry 02/2010; 58(6):3342-9. · 2.82 Impact Factor
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ABSTRACT: Fifteen new derivatives of D-DIBOA, including aromatic ring modifications and the addition of side chains in positions C-2 and N-4, were synthesized and their phytotoxicity, selectivity, and structure-activity relationships evaluated. The most active compounds among the derivatives at the C-2 position were 6-Cl-2-Et-D-DIBOA and 6-F-2-Et-D-DIBOA. Of the derivatives at N-4, the most active compounds were 6-Cl-4-Pr-D-DIBOA and 6-Cl-4-Val-D-DIBOA. These four compounds showed high levels of inhibition in root length at very low concentrations in all species. The most remarkable result is the 70% inhibition observed for the root length of cress at 100 nM caused by the latter two compounds. These results support our previous research and conclusions regarding the steric, electronic, and solubility requirements to achieve the maximum phytotoxic activity.
Journal of Agricultural and Food Chemistry 12/2009; 58(3):2047-53. · 2.82 Impact Factor
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ABSTRACT: Benzoxazinones (BAs) are natural products that are present in Gramineae and represent part of the plant defence system against pests. In recent years, sprouts of maize, wheat and rye have been used for the production of dietary supplements. We have investigated the potential genotoxic activities of a diverse range of synthetic derivatives of the most abundant natural BA, namely DIBOA (2,4-dihydroxy-1,4-benzoxazin-3-one), proposed for use as a potential herbicide. We have tested 18 synthetic BAs for potential effects in cultured HeLa cells. We found significantly higher micronucleus (MN) induction over the background level, with the solvent DMSO used as an internal control. Concentration-dependent effects were found between 1nM and 20nM for all the synthetic compounds studied. Immunostaining with an anticentromere antibody showed that >80% of MN induced gave a centromere-positive signal. Similarly, fluorescence in situ hybridization (FISH) analysis with alphoid centromere probes showed a positive hybridization signal, indicating that all compounds analyzed are aneugenic. Chemical modification of the N in the heterocyclic aromatic amine served us to suggest a relationship between the structure and the aneugenic effects of the compounds analyzed. Our findings indicate that benzoxazinoids could be potential genotoxins for human cells.
Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis 12/2009; 695(1-2):81-6. · 2.85 Impact Factor
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ABSTRACT: Compounds of the (2H)-1,4-benzoxazin-3(4H)-one class have attracted the attention of phytochemists since the first isolation of 2,4-dihydroxy-2H-1,4-benzoxazin-3(4H)-one (DIBOA) and 2,4-dihydroxy-7-methoxy-(2H)-1,4-benzoxazin-3(4H)-one (DIMBOA). Extensive research has been carried out on the isolation and synthesis of these materials as well as on the dynamics of their degradation in different systems. This has led to the discovery of a wide variety of compounds that are of high interest from the point of view of phytotoxic, antifungal, antimicrobial, and antifeedant effects among others. The potential application of benzoxazinones and their derivatives as leads for natural herbicide models is a topic of current interest. Furthermore, the importance of degradation on the ecological behaviour of benzoxazinone-producing plants is also being realised, and proposals concerning the role of the degradation products in chemical defence mechanisms have been put forward. There is also increasing interest in the improvement of analytical methodologies, and ecotoxicologic effects, toxicity on target and non-target organisms, and degradation kinetics are also being addressed. The development of new phytotoxicity bioassay techniques represents one of the most important breakthroughs in this respect. Moreover, benzoxazinones and some of their derivatives have been employed in the development of pharmaceuticals. The versatility of the benzoxazinone skeleton, in addition to its relative chemical simplicity and accessibility, makes these chemicals amongst the most promising sources of bioactive compounds that are natural in origin.
Natural Product Reports 05/2009; 26(4):478-89. · 9.79 Impact Factor
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ABSTRACT: A new ent-kaurane glucoside, named helikauranoside A (4), was isolated from the aerial parts of Helianthus annuus L. together with three known ent-kaurane-type diterpenoids: (-)-kaur-16-en-19-oic acid (1), grandifloric acid (2), and paniculoside IV (3). The structure of 4 was determined by using a combination of 1D (1H-NMR and 13C-NMR) and 2D (COSY, HSQC, and HMBC) NMR techniques. Bioactivity spectra of isolated compounds were tested by using the etiolated wheat coleoptile bioassay in aqueous solutions at concentrations ranging from 10(-3) to 10(-6)M. Helikauranoside A (4) was the most active (-84%, 10(-3)M; -56%, 10(-4)M). These results suggest that this new compound may be involved in defense mechanisms of H. annuus.
Journal of Chemical Ecology 02/2008; 34(1):65-9. · 2.66 Impact Factor
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ABSTRACT: Allelopathy studies the interactions among plants, fungi, algae and bacteria with the organisms living in a certain ecosystem, interactions that are mediated by the secondary metabolites produced and exuded into the environment. Consequently, allelopathy is a multidisciplinary science where ecologists, chemists, soil scientists, agronomists, biologists, plant physiologists and molecular biologists offer their skills to give an overall view of the complex interactions occurring in a certain ecosystem. As a result of these studies, applications in weed and pest management are expected in such different fields as development of new agrochemicals, cultural methods, developing of allelopathic crops with increased weed resistance, etc. The present paper will focus on the chemical aspects of allelopathy, pointing out the most recent advances in the chemicals disclosed, their mode of action and their fate in the ecosystem. Also, attention will be paid to achievements in genomics and proteomics, two emerging fields in allelopathy. Rather than being exhaustive, this paper is intended to reflect a critical vision of the current state of allelopathy and to point to future lines of research where in the authors' opinion the main advances and applications could and should be expected.
Pest Management Science 05/2007; 63(4):327-48. · 2.25 Impact Factor
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ABSTRACT: The utility of benzoxazinones and some of their synthetic derivatives in the search for new leads for herbicide model development has been widely discussed. As the benzoxazinone skeleton contains three different potential areas for functionalization (C-2, N-4, and aromatic protons H-5, H-6, H-7, and H-8), and the first two have already been optimized, the main objective of this work was the substitution of aromatic protons for different substituent types and the study of the effects of the prepared chemicals on selected standard target species (STS) and weeds. Thus, different combinations of aromatic substituents, including methoxy, methoxycarbonyl, fluorine, chlorine, and trifluoromethyl, were introduced at different positions. Phytotoxicity results were successfully correlated with steric and electronic molecular parameters, the resulting molecular volume (V) and dipole moment (mu) being the most influential ones. Halogenations at C-6 and fluorination at C-7 were the most successful modifications. Compounds 6-fluoro-(2H)-1,4-benzoxazin-3(4H)-one (6F-D-DIBOA), 7-fluoro-(2H)-1,4-benzoxazin-3(4H)-one (7F-D-DIBOA), and 6-chloro-(2H)-1,4-benzoxazin-3(4H)-one (6Cl-D-DIBOA) had the highest phytotoxic activities. The dose-response profiles on wheat and two of its most common weeds (Lolium rigidum Gaud. and Avena fatua L.) were compared by means of a proposed selectivity index, which displayed 7F-D-DIBOA as the most selective of the tested benzoxazinones.
Journal of Agricultural and Food Chemistry 01/2007; 54(26):9843-51. · 2.82 Impact Factor
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ABSTRACT: Benzoxazinones are plant allelochemicals well-known for their phytotoxic activity and for taking part in the defense strategies of Gramineae, Ranunculaceae, and Scrophulariceae plants. These properties, in addition to the recently optimized methodologies for their large-scale isolation and synthesis, have made some derivatives of natural products, 2,4-dihydroxy-(2H)-1,4-benzoxazin-3-(4H)-one (DIBOA) and its 7-methoxy analogue (DIMBOA), successful templates in the search for natural herbicide models. These new chemicals should be part of integrated methodologies for weed control. In ongoing research about the structure-activity relationships of benzoxazinones and the structural requirements for their phytotoxicity enhancement and after characterization of the optimal structural features, a new generation of chemicals with enhanced lipophilicity was developed. They were tested on selected standard target species and weeds in the search for the optimal aqueous solubility-lipophilicity rate for phytotoxicity. This physical parameter is known to be crucial in modern drug and agrochemical design strategies. The new compounds obtained in this way had interesting phytotoxicity profiles, empowering the phytotoxic effect of the starting benzoxazinone template in some cases. Quantitative structure-activity relationships were obtained by bioactivity-molecular parameters correlations. Because optimal lipophilicity values for phytotoxicity vary with the tested plant, these new derivatives constitute a more selective way to take advantage of benzoxazinone phytotoxic capabilities.
Journal of Agricultural and Food Chemistry 01/2007; 54(25):9357-65. · 2.82 Impact Factor
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ABSTRACT: From the medium, polar bioactive fractions of leaf aqueous extract of Helianthus annuus L., heliespirones B (2) and C (3) have been isolated. The structural elucidation was based on extensive spectral studies. A probable biogenesis of heliespirone skeleton is proposed and discussed. The structure of heliespirone B has been confirmed by X-ray diffraction analysis.
Organic Letters 10/2006; 8(20):4513-6. · 5.86 Impact Factor
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ABSTRACT: Rice is one of the most interesting crops in the world from both the social and the economic point of views. The monoculture practices along with the heavy use of herbicides are characteristic of modern agriculture and are inducing the appearance of tolerant and/or herbicide resistant weed biotypes. This is the case the world's main weed of rice barnyardgrass (Echinochloa crus-galli). Alternative strategies for weed suppression consist of the use of chemicals from rice due to necessity of obtaining new herbicides with new modes of action that could prevent resistance phenomena. In order to carry out a study that guides to the isolation of the most active compounds from rice, different extracts were achieved, and their activities evaluated. So, all the plant material was divided into three parts: fresh plant, dried plant, and fresh plant from Pluviotron. The aerial part was separated from roots in all cases and extracted in water, in organic solvents as well as with the Pluviotron device. The activity of the 12 extracts obtained was evaluated using a generalist bioassay, wheat etiolated coleoptiles bioassay, and a phytotoxic bioassay on barnyardgrass as target species. The bioactive extracts were fractionated and 15 compounds were isolated and identified by spectroscopic methods. Eight of these compounds were isolated for the first time in Oryza sativa. The most phytotoxic compounds on E. crus-galli were ergosterol peroxide and 7-oxo-stigmasterol. In the case of ergosterol peroxide the activity was higher than the commercial herbicide Logran. This is the first report of potential allelopathic activity of steroids on weeds based on their phytotoxicity.
Steroids 08/2006; 71(7):603-8. · 2.83 Impact Factor
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ABSTRACT: Six new sesquiterpene lactones, annuolide H (3), helivypolides F, H-J (4, 11-13), and helieudesmanolide A (6), together with known compounds, were isolated from polar bioactive fractions of Helianthus annuus cv. SH-222 and Stella fresh leaf water extracts. Spectroscopic analysis of the new data for 1,2-anhydroniveusin A and 1-methoxy-4,5-dihydroniveusin A corrects some previous assignments. The compounds were tested using the etiolated wheat coleoptile bioassay, and the most active compounds were assayed in standard target species (STS) (Lepidium sativum, Allium cepa, Lactucasativa, Lycopersicon esculentum, and Triticum aestivum) from 5 x 10(-4) to 10(-5) M. The most phytotoxic compounds were helivypolide F and 15-hydroxy-3-dehydrodeoxyfruticin, both of which have a carbonyl group at C-3 conjugated with two double bonds.
Journal of Natural Products 06/2006; 69(5):795-800. · 3.13 Impact Factor
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ABSTRACT: Avena fatua L. (wild oat) and Lolium rigidum Gaud. (rigid ryegrass) are highly problematic weeds affecting a wide variety of cereal crops worldwide. The fact that both of these weeds have developed resistance to several herbicide groups made them optimal candidates as target organisms for ongoing research about the potential application of allelochemicals and analogue compounds as natural herbicide models. Benzoxazinones, a family of natural allelochemicals present in corn, wheat, and rye, including 2,4-dihydroxy-(2H)-1,4-benzoxazin-3(4H)-one and 2,4-dihydroxy-7-methoxy-(2H)-1,4-benzoxazin-3(4H)-one, together with some degradation products, found in crop soils as well as in other systems, and some synthetic analogues of them were tested on wild oat and rigid ryegrass seeds; the results were statistically treated, and some structure-activity relationships, useful in further development of natural herbicide models, were elucidated. The most active compounds were the synthetic benzoxazinone 2-acetoxy-(2H)-1,4-benzoxazin-3(4H)-one and the degradation product 2-aminophenoxazin-3-one, with highly significant inhibition on the development of both weeds. The ecological role of these compounds is discussed by considering both degradability and phytotoxicity. The bioactivity of aminophenoxazines has been correlated by their aqueous solubility-lipophilicity predicted by means of computational methods.
Journal of Agricultural and Food Chemistry 03/2006; 54(4):1040-8. · 2.82 Impact Factor
