[Show abstract][Hide abstract]ABSTRACT: Botanical biopesticides constitute an important tool for Integrated Pest Management practices. Uruguay has a great potential for developing botanical biopesticides from its abundant native flora. Dodonaea viscosa Jacq. is a native Sapindaceae that in preliminary studies was shown to possess a potential deterrent activity against insect models. In this work, ethanolic extracts of the leaves of this species were studied. Bioguided fractionation and supercritical fluid extraction led to the isolation of active compounds. For that purpose four insect models were used: Epilachna paenulata, Spodoptera littoralis, Myzus persicae, and Rhopalosiphum padi, which are pests of crops of economic importance. Lupeol, stigmasterol, stigmast-7-en-3-ol, and a labdane diterpene were isolated and showed differential activity against the models.
[Show abstract][Hide abstract]ABSTRACT: Secondary metabolites from plants have been the source of various natural products with anti-insect properties; having some of them already reached the market. In recent years, the drawbacks related to the use of synthetic pesticides have triggered the need to find alternatives and brought about revitalization on bioprospecting programs. In that direction, this work presents the results of a study on a South American native species. The methanolic leaf extract of Clytostoma callistegioides (Bignoniaceae), was hydrolyzed with HCl, and sequentially subjected to Sephadex LH20 and HPLC procedures. Three flavones, not previously obtained from this species, were identified by NMR and UV spectra: 4′-Hydroxywogonin, Acacetin and Galangustin. Two important agricultural pests, Myzus persicae and Rhopalosiphum padi (Hemiptera: Aphididae), were studied in their reluctance to settling on leaf treated with these flavonoids, and the results are here reported in terms of a preference index (PI), calculated as PI = [(%C − %T)/(%C + %T)]; where %C and %T are the percentages of aphids settled on the treated and the control leaf pieces, respectively. While 4′-Hydroxywogonin did not exhibit significant activity against neither of the aphids, Acacetin was active only against R. padi (PI = 0.3 ± 0.1). Further, Galangustin exhibited a better deterrence activity on the settling of both aphids (PI = 0.4 ± 0.1 and 0.8 ± 0.1 for M. persicae and R. padi respectively).
Full-text · Article · Jan 2013 · Industrial Crops and Products
[Show abstract][Hide abstract]ABSTRACT: Bulnesia sarmientoi Lorentz ex Griseb volatile oil was characterized by GC×GC-TOF-MS analysis. Major components were guaiol and bulnesol, followed by hanamyol. The enhanced sensitivity and superior resolution of GC×GC resulted in the identification of thus-far unreported oil constituents as β-guaiene, guaioxide, elemol, germacrene-B, eudesm-5-en-11-ol, γ-eudesmol, α-eudesmol and (−)-hanamyol. The insecticidal effect of B. sarmientoi oil and its main constituents (guaiol, bulnesol and hanamyol) on Spodoptera littoralis, Rhopalosiphum padi and Myzus persicae was studied. Guaiol affected the aphids in a dose-response fashion, showing low efficiency, while bulnesol and hanamyol were inactive. Both the oil and its constituents were also assayed for antifungal action against Fusarium spp. and phytotoxicity to Lactuca sativa. Among the pure compounds tested, bulnesol had a low-moderate effect on Fusarium moniliforme while hanamyol had a strong effect on Fusarium solani. Neither the oil nor the tested compounds affected L. sativa germination or radicle length, indicating that B. sarmientoi is not phytotoxic.
Full-text · Article · Mar 2011 · Industrial Crops and Products
[Show abstract][Hide abstract]ABSTRACT: A bioassay-guided fractionation of leaf extracts from Clytostoma callistegioides (Cham.) Bureau ex Griseb. (Bignoniaceae) led to isolation of a natural mixture of four fatty acids with anti-insect activity against aphids. The compounds were identified by GC-MS as palmitic, stearic, linoleic and linolenic acids and quantified as their methyl esters. The anti-aphid activity of the natural mixture was traced to linolenic and linoleic acids, as shown by the settling inhibition activity of synthetic samples. Interestingly, the saturated acids (palmitic and stearic) tested alone stimulated settling on one of the tested aphids (Myzus persicae), but not on the other tested species (Rhopalosiphum padi). Although ubiquitous, none of these free acids have been previously reported in this Bignoniaceae species. The leaf surface chemistry, which is likely involved in modulating aphid settling behavior, was further investigated for the occurrence of lipophilic substances by histochemical staining. Short, stalked glandular trichomes, previously undescribed for this species, stained with osmium tetroxide and Sudan III, suggesting that the secretion of the defensive acids is related to these surface trichomes.
[Show abstract][Hide abstract]ABSTRACT: Members of the family Bignoniaceae are mostly found in tropical and neo-tropical regions in America, Asia and Africa, although some of them are cultivated in other regions as ornamentals. Species belonging to this family have been extensively studied in regard to their pharmacological properties (as extracts and isolated compounds). The aim of this review is to summarize the reported scientific evidence about the chemical properties as well as that of the extracts and isolated compounds from species of this family, focusing mainly in insect-plant interactions. As it is known, this family is recognized for the presence of iridoids which are markers of oviposition and feeding preference to species which have became specialist feeders. Some herbivore species have also evolved to the point of been able to sequester iridoids and use them as defenses against their predators. However, iridoids also exhibit anti-insect properties, and therefore they may be good lead molecules to develop botanical pesticides. Other secondary metabolites, such as quinones, and whole extracts have also shown potential as anti-insect agents.
[Show abstract][Hide abstract]ABSTRACT: We evaluated the anti-insectan activity of extracts from different vegetative parts of ten plant species native to Uruguay. The selected plants belong to five families: Bignoniaceae: Clytostoma callistegioides, Dolichandra cynanchoides, Macfadyena unguis-cati; Sapindaceae: Dodonaea viscosa, Allophylus edulis, Serjania meridionalis; Lamiaceae: Salvia procurrens, Salvia guaranitica; Solanaceae: Lycium cestroides; and Phytolaccaceae: Phytolacca dioica. The extracts were evaluated in independent bioassays against four insect pests and one beneficial insect. Aphid settling inhibition was evaluated with a grass specialist, Rhopalosiphum padi, and a feeding generalist, Myzus persicae (both Hemiptera: Aphididae). Antifeedant activity was tested with adults of the specialist Epilachna paenulata (Coleoptera: Coccinellidae) and larvae of the generalist Spodoptera littoralis (Lepidoptera: Noctuidae). Finally, contact toxicity was assessed with honey bees, Apis mellifera (Hymenoptera: Apidae). Strong settling inhibition (SI) activity (expressed as %SI, where 100% means complete inhibition by the extract) was found only for the twig extracts of A. edulis (Sapindaceae) against M. persicae (% SI = 77 +/- 4). Antifeedant activity (expressed as % of feeding reduction (FR), where 100% means no consumption on extract-treated diet) against E. paenulata was significant for the leaf extracts of L. cestroides (Solanaceae) (% FR = 100 +/- 0) as well as of all Bignoniaceae and Sapindaceae species. No extracts were active against S. littoralis larvae, and most of them were innocuous to honey bees, with the exception of L. cestroides and S. meridionalis leaf extracts.
Full-text · Article · Jan 2009 · Industrial Crops and Products
[Show abstract][Hide abstract]ABSTRACT: The sesquiterpene p-benzoquinone perezone (1), isolated from Perezia adnata var. alamani (Asteraceae), and its non-natural derivatives isoperezone (2), dihydroperezone (3), dihydroisoperezone (4), and anilidoperezone (5) were tested as antifeedants against the herbivorous insects Spodoptera littoralis, Leptinotarsa decemlineata, and Myzus persicae. Compounds 1-5 exhibited strong antifeedant activity against L. decemlineata and M. persicae, and elicited a low response by S. littoralis. Antifeedant activity on L. decemlineata and M. persicae increased when the hydroxyl group at C-3 in perezone (1) was changed to C-6 to give isoperezone (2). The same effect was found with hydrogenation of the double bond of the alkyl chain of (1) to yield dihydroperezone (3). In contrast, hydrogenation of this double bond in isoperezone (2) to give dihydroisoperezone (4) led to a reduction in antifeedant activity. Determination of the phytotoxic activity of 1-5 revealed that 3 had a significant inhibition effect on Lactuca sativa radicle length growth.
Full-text · Article · Jul 2008 · Journal of Chemical Ecology
[Show abstract][Hide abstract]ABSTRACT: We investigated the qualitative and quantitative seasonal variation of the leaf and fruit oils of the Macaronesian endemism Laurus novocanariensis and their plant defensive potential. The monoterpene fraction dominated the leaf (74%) and berry essential oils (73–44%, ripe–unripe). The insect antifeedant effects of these oils were species- and season-dependent against the aphids (Myzus persicae and Rhopalosiphum padi). Overall, the biological effects of these oils correlated with the oxygenated terpene fraction. Among the pure components tested, β-caryophyllene and its oxide were strong antifeedants to Leptinotarsa decemlineata and Spodoptera littoralis. The aphids responded to β-ocimene, β-pinene, 1,8-cineole, linalool (antifeedants) and linalool oxide (attractive to M. persicae). The antifungal effects of the leaf oils on Fusarium spp. were season-dependent. β-Caryophyllene oxide proved to be a strong antifungal. L. novocanariensis oils inhibited Lactuca sativa germination and radicle elongation, the leaves being more effective. Linalool also inhibited seed germination.
Full-text · Article · Mar 2008 · Biochemical Systematics and Ecology
[Show abstract][Hide abstract]ABSTRACT: The insect antifeedant and toxic activity of hydroxyperezone (1), its derivatives 2-9, along with 3-hydroxy- (10) and 6-hydroxythymoquinone (11) were studied against Spodoptera littoralis, Leptinotarsa decemlineata, and Myzus persicae. The antifeedant tests showed that L. decemlineata was the most sensitive insect, followed by M. persicae, while S. littoralis was not deterred by compounds 1-11. Leucohydroxyperezone tetraacetate (3), oxoperezinone (6), dihydroleucoperezinone diacetate (7), 3-hydroxy- (10) and 6-hydroxythymoquinone (11) showed strong activity against L. decemlineata. 1 and 7 exhibited moderate deterrent activity against M. persicae, while 1 and dihydroleucohydroxyperezone tetraacetate (4) acted as post-ingestive antifeedants to S. littoralis. The phytotoxic activity of compounds 1-11 was also evaluated. Hydroxyperezone (1) strongly inhibited seed germination at 24 h, while the activity of 3-8 and 10 was moderate. The level of radicle growth inhibition obtained with compounds 1-5 and 8-11 was significant (< 50%).
Full-text · Article · Mar 2008 · Zeitschrift fur Naturforschung C
[Show abstract][Hide abstract]ABSTRACT: The head lice, Pediculus humanus capitis (Phthiraptera:Pediculidae), is an obligate ectoparasite of humans that causes pediculosis capitis, a nuisance for millions
of people worldwide, with high prevalence in children. Pediculosis capitis has been treated by methods that include the physical
remotion of lice, various domestic treatments and conventional insecticides. None of these methods render complete protection,
and there is clear evidence for the evolution of resistance and cross-resistance to conventional insecticides. Non-toxic alternative
options are hence needed for head lice treatment and/or prevention, and natural products from plants, especially essential
oils (EOs), are good candidates for safer control agents that may provide good anti-lice activity and low levels of evolved
resistance. A few EOs have been tested as repellents with promissory results, although often in vitro tests and clinical trials
produce contradictory results. A handful of fixed extracts and several EOs and their individual components have also been
tested as contact pediculicides or fumigants. The studies have focused mainly on plant families characterized for the production
of EOs. While many EOs and individual compounds showed pediculicide activity, comparing results is difficult due to the diverse
bioassay methodologies. Studies of anti-lice activity of individual EO components provide the basis for preliminary conclusions
of structure–activity relationships, although no clear patterns can yet be drawn. We here attempt to provide a concise compilation
of the available information on anti-lice activity of plant extracts and plant-derived compounds, which we hope may be of
help for future developments in this area.
Full-text · Article · Jan 2008 · Phytochemistry Reviews