Publicação
Plant-based pesticides: Potential of apiaceae essential oils
| Resumo: | The development of biopesticides follows a strong rising trend over the last two decades, and a continued growth of the global biopesticides market is forecasted. This phenomenon is largely supported by the growing awareness to environmentally friendly food production and the introduction of restrictive regulations for pesticides. In light of their multiples advantage over synthetic pesticides, biopesticides appear economical, eco-friendly and less prone to the development of resistance, and hence are expected to provide more environmentally sustainable methods of biocontrol (Czaja et al., 2015). In fact, biopesticides have been integrated in several pest and vector management programs. As a complementary approach or alternative to synthetic pesticides, phytochemicals, namely essential oils (EOs) and volatile compounds are incorporated into crop protection products, as well as repellent formulations (Regnault- Roger et al., 2012). The best market opportunities have been assigned to EO-based pesticides, owing to the great availability, GRAS status, chemical simplicity, relatively low toxicity to vertebrates and specific mode-of-action of their constituents (Isman & Akhtar, 2007; Shaaya & Rafaeli, 2007). In this context, the Apiaceae (=Umbelliferae) family, which comprised economically important plants species, presents a wide variety of bioactive compounds being also an important source of EOs and volatile compounds distributed by several distinct chemicals classes. Aware of their traditional use, their relatively large worldwide production and the bioactive potential described by many authors, we proposed to perform an appraisal of the biopesticidal potential of well-known Apiaceae species, whose experimental approach, results and discussion are here reported. In a few words, this work consisted in: (1) the characterization of EOs extracted from different plant parts of four species [Anethum graveolens (dill), Cuminum cyminum (cumin), Foeniculum vulgare var. vulgare (bitter fennel), Petroselinum crispum (plain leaf parsley)] and (2) the toxicological evaluation of some EOs and individual constituents, using as target organisms a mosquito (Anopheles atroparvus), a lepidopteran (Pseudaletia unipuncta) and a freshwater snail (Radix peregra). The anti-nematode properties of bitter fennel EOs and two phenylpropanoids against Meloidogyne javanica was also evaluated. EOs were isolated by hydrodistillation and chemically characterized by GC and GC-MS. Quantitative data were obtained using GC-FID and the identification of constituents was achieved with the help of spectra libraries and determination of their KI. The overall identification of their content ranged between 88 and 99.5%. The EOs content (ranging between 0.10-3.45%) and chemical profiles were highly variable depending of the organ type, developmental stage and origin of the material. The development of dill umbels from the pre-flowering to the ripe fruit stage was accompanied by a significant increase of (S)- carvone (from 4 to 61% of the EO content) and a reduction of α-phellandrene and dill ether contents. Bitter fennel infrutescences and leaves plus stems EOs were mainly composed by estragole (64 and 28%, respectively), followed by α-phellandrene, α-pinene and fenchone. We also identified intra-individual variations in the cultivated population of bitter fennel. Concerning cumin EOs, all fruit samples and the commercial EO were mainly constituted by cuminaldehyde (28-39 %), followed by variable amounts of pmentha- 1,4-dien-7-al, p-mentha-1,3-dien-7-al, β-pinene, p-cymene and γ-terpinene. EOs from parsley were the most complex of the four species, being characterized by a high percentage of hydrocarbon monoterpenes and several phenylpropenes (myristicin, apiole, elemicin and/or allyltetramethoxybenzene). The activity of EOs and individual compounds was assessed against A. atroparvus (3rd instar larvae), P. unipuncta (eggs and larvae) and R. peregra (eggs, juveniles and adults). Bitter fennel EOs were also tested against eggs and juveniles of M. javanica. Whenever possible, mortality (%) was recorded for a range of optimized concentrations or at different times of exposure, and the lethal parameters for 50 % and 90% (lethal concentrations, LCs, and/or lethal times, LTs) were estimated by Log-Probit analysis. EOs from parsley, cumin and bitter fennel (leaves more stems) were highly active towards the snail (both eggs and adults) and the mosquito larvae. Estimated LC50 against adult snails varied from 13.7 to 46.5 mg L-1 (48 h), and from 16 to 143 mg L-1 (24 h) against the mosquito larvae, with parsley fruit EO being the most doseeffective one in both situations. A short-time exposure (8 h) to bitter fennel EOs was also effective for snail control. Regarding assays performed on P. unipuncta, dill, cumin and parsley EOs, as well as the compounds (S)-carvone, cuminaldehyde and myristicin, showed satisfactory egg hatching inhibition, and acute contact toxicity to the 4th instar larvae (24 h-LC50 ranging from 108 to 197 μg cm-2). Dill, cumin and bitter fennel EOs and some of their constituents were effective by fumigation (≥80%). In addition, the EO from parsley fruits, trans-anethole and cuminaldehyde displayed significant feeding deterrence and growth inhibition (FDI and GI >70%), when performing the no-choice assay with treated corn leaves, causing significant negative impact on the metabolism of this lepidopteran. Parsley fruits EO was of great efficacy against P. unipuncta, acting as ovicide, larvicide (by contact), feeding deterrent and growth inhibitor. Its constituents myristicin and apiole (purified by CC) showed similar effectiveness in several assays. Besides, we distinguish the phenylpropanoid trans-anethole (a constituent of bitter fennel EOs) for its acute insecticidal, nematicidal and molluscicidal activities, being more active than its isomer (estragole). The present study demonstrates that EOs from the four studied Apiaceae species, along with some of their major compounds, have moderate to strong anti-insect and molluscicidal properties. EOs and compounds showed distinct performances depending on the type of assay, the exposure period, the tested organism and/or its developmental stage. In general, the reproductive organs (umbels-bearing fruits and eventually ripen fruits) were optimum sources of EOs containing the highest percentage of biologically active compounds (except bitter fennel). As a whole, the results demonstrates that the four plant species are promising sources of botanical biopesticides in the context of the biochemical control of phytophagous insects and vectors of human and animal diseases. |
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| Autores principais: | Sousa, Rose Marie Oliveira Ferreira de |
| Assunto: | Ciências Naturais::Ciências Biológicas |
| Ano: | 2016 |
| País: | Portugal |
| Tipo de documento: | tese de doutoramento |
| Tipo de acesso: | acesso aberto |
| Instituição associada: | Universidade do Minho |
| Idioma: | português |
| Origem: | RepositóriUM - Universidade do Minho |
| Resumo: | The development of biopesticides follows a strong rising trend over the last two decades, and a continued growth of the global biopesticides market is forecasted. This phenomenon is largely supported by the growing awareness to environmentally friendly food production and the introduction of restrictive regulations for pesticides. In light of their multiples advantage over synthetic pesticides, biopesticides appear economical, eco-friendly and less prone to the development of resistance, and hence are expected to provide more environmentally sustainable methods of biocontrol (Czaja et al., 2015). In fact, biopesticides have been integrated in several pest and vector management programs. As a complementary approach or alternative to synthetic pesticides, phytochemicals, namely essential oils (EOs) and volatile compounds are incorporated into crop protection products, as well as repellent formulations (Regnault- Roger et al., 2012). The best market opportunities have been assigned to EO-based pesticides, owing to the great availability, GRAS status, chemical simplicity, relatively low toxicity to vertebrates and specific mode-of-action of their constituents (Isman & Akhtar, 2007; Shaaya & Rafaeli, 2007). In this context, the Apiaceae (=Umbelliferae) family, which comprised economically important plants species, presents a wide variety of bioactive compounds being also an important source of EOs and volatile compounds distributed by several distinct chemicals classes. Aware of their traditional use, their relatively large worldwide production and the bioactive potential described by many authors, we proposed to perform an appraisal of the biopesticidal potential of well-known Apiaceae species, whose experimental approach, results and discussion are here reported. In a few words, this work consisted in: (1) the characterization of EOs extracted from different plant parts of four species [Anethum graveolens (dill), Cuminum cyminum (cumin), Foeniculum vulgare var. vulgare (bitter fennel), Petroselinum crispum (plain leaf parsley)] and (2) the toxicological evaluation of some EOs and individual constituents, using as target organisms a mosquito (Anopheles atroparvus), a lepidopteran (Pseudaletia unipuncta) and a freshwater snail (Radix peregra). The anti-nematode properties of bitter fennel EOs and two phenylpropanoids against Meloidogyne javanica was also evaluated. EOs were isolated by hydrodistillation and chemically characterized by GC and GC-MS. Quantitative data were obtained using GC-FID and the identification of constituents was achieved with the help of spectra libraries and determination of their KI. The overall identification of their content ranged between 88 and 99.5%. The EOs content (ranging between 0.10-3.45%) and chemical profiles were highly variable depending of the organ type, developmental stage and origin of the material. The development of dill umbels from the pre-flowering to the ripe fruit stage was accompanied by a significant increase of (S)- carvone (from 4 to 61% of the EO content) and a reduction of α-phellandrene and dill ether contents. Bitter fennel infrutescences and leaves plus stems EOs were mainly composed by estragole (64 and 28%, respectively), followed by α-phellandrene, α-pinene and fenchone. We also identified intra-individual variations in the cultivated population of bitter fennel. Concerning cumin EOs, all fruit samples and the commercial EO were mainly constituted by cuminaldehyde (28-39 %), followed by variable amounts of pmentha- 1,4-dien-7-al, p-mentha-1,3-dien-7-al, β-pinene, p-cymene and γ-terpinene. EOs from parsley were the most complex of the four species, being characterized by a high percentage of hydrocarbon monoterpenes and several phenylpropenes (myristicin, apiole, elemicin and/or allyltetramethoxybenzene). The activity of EOs and individual compounds was assessed against A. atroparvus (3rd instar larvae), P. unipuncta (eggs and larvae) and R. peregra (eggs, juveniles and adults). Bitter fennel EOs were also tested against eggs and juveniles of M. javanica. Whenever possible, mortality (%) was recorded for a range of optimized concentrations or at different times of exposure, and the lethal parameters for 50 % and 90% (lethal concentrations, LCs, and/or lethal times, LTs) were estimated by Log-Probit analysis. EOs from parsley, cumin and bitter fennel (leaves more stems) were highly active towards the snail (both eggs and adults) and the mosquito larvae. Estimated LC50 against adult snails varied from 13.7 to 46.5 mg L-1 (48 h), and from 16 to 143 mg L-1 (24 h) against the mosquito larvae, with parsley fruit EO being the most doseeffective one in both situations. A short-time exposure (8 h) to bitter fennel EOs was also effective for snail control. Regarding assays performed on P. unipuncta, dill, cumin and parsley EOs, as well as the compounds (S)-carvone, cuminaldehyde and myristicin, showed satisfactory egg hatching inhibition, and acute contact toxicity to the 4th instar larvae (24 h-LC50 ranging from 108 to 197 μg cm-2). Dill, cumin and bitter fennel EOs and some of their constituents were effective by fumigation (≥80%). In addition, the EO from parsley fruits, trans-anethole and cuminaldehyde displayed significant feeding deterrence and growth inhibition (FDI and GI >70%), when performing the no-choice assay with treated corn leaves, causing significant negative impact on the metabolism of this lepidopteran. Parsley fruits EO was of great efficacy against P. unipuncta, acting as ovicide, larvicide (by contact), feeding deterrent and growth inhibitor. Its constituents myristicin and apiole (purified by CC) showed similar effectiveness in several assays. Besides, we distinguish the phenylpropanoid trans-anethole (a constituent of bitter fennel EOs) for its acute insecticidal, nematicidal and molluscicidal activities, being more active than its isomer (estragole). The present study demonstrates that EOs from the four studied Apiaceae species, along with some of their major compounds, have moderate to strong anti-insect and molluscicidal properties. EOs and compounds showed distinct performances depending on the type of assay, the exposure period, the tested organism and/or its developmental stage. In general, the reproductive organs (umbels-bearing fruits and eventually ripen fruits) were optimum sources of EOs containing the highest percentage of biologically active compounds (except bitter fennel). As a whole, the results demonstrates that the four plant species are promising sources of botanical biopesticides in the context of the biochemical control of phytophagous insects and vectors of human and animal diseases. |
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