RESUMEN
In the context of climate change, the Ivorian cotton industry is facing with the loss of sensitivity of pests (Helicoverpa armigera) and the appearance of new so-called emerging insects. Faced with this situation, cotton producers tend to use insecticide products in high doses, in excess of the norm. However, the misuse of chemical products poses many health risks. Therefore, to limit the use of chemicals, aqueous extracts of local plants with insecticidal properties were examined in the laboratory and in the field. Four local plant species were selected [Anacardium occidentale (Anarcardier); Azadirachta indica (Neem); Hyptis suaveolens (Hyptis) and Tephrosia vogelii (Tephrosia)]. After determining the chemical profiles of the four extracts by high performance liquid chromatography (HPLC)-mass spectrometry, their inhibitory activities were assessed in cholinesterase and tyrosinase. The sensitivity of Helicoverpa armigera larvae was evaluated by ingesting the aqueous extracts at several concentrations ranging from 2% to 64% in an artificial nutrient substrate. Then, the mortality rates of the larvae during 72 h were evaluated and the lethal concentrations were determined. The results of chemical analyses (HPLC) showed that the richest aqueous extract in phytochemicals with 54 elements detected was that of cashew (A. occidentale). T. vogelii, A. indica and H. suaveolens presented 44, 45, and 39 chemical compounds, respectively. In addition, the total phenolic content was higher in A. occidentale (110.67 mg gallic acid equivalents/g) followed by A. indica (42.43 mg gallic acid equivalents/g). The highest antioxidant ability was observed with the aqueous extract of cashew (A. occidentale). Anti-enzymatic activities such as acetylcholinesterase, butyrylcholinesterase and tyrosinase inhibition were most pronounced in A. occidentale (2.35 ± 0.02 mg galanthamine equivalent/g, 3.77 ± 0.01 mg galanthamine equivalent/g and 71.28 ± 0.07 mg kojic acid equivalent/g, respectively). The most toxic aqueous extract for H. armigera larvae was that of cashew with a lethal concentration LC50 = 11.68%. Moreover, the principal component analysis performed showed that the insecticidal activity is strongly correlated with the antioxidant and enzymatic activities of the aqueous extracts. Then, the hierarchical ascending classification showed cashew as the best plant. For the sustainability of cotton production, it would be necessary to limit the use of chemical-synthetic insecticides through the use of plant extracts, especially from cashew leaves.
Asunto(s)
Insecticidas , Mariposas Nocturnas , Animales , Larva , Insecticidas/farmacología , Insecticidas/química , Antioxidantes/farmacología , Côte d'Ivoire , Gossypium , Galantamina , Acetilcolinesterasa , Butirilcolinesterasa , Monofenol Monooxigenasa , Extractos Vegetales/farmacología , Ácido GálicoRESUMEN
Faced with the serious consequences resulting from the abusive and repeated use of synthetic chemicals, today rethinking crop protection is more than necessary. It is in this context that the essential oils of the Lamiaceae Ocimum gratissimum and Ocimum canum, the Poaceae Cymbopogon citratus and nardus and a Rutaceae Citrus sp. of known chemical compositions were experimented. The evaluation of the larvicidal potential of the essential oils was done by the method of topical application of the test solutions, on the L1-L2 stage larvae from the first generation of S. frugiperda obtained after rearing in an air-conditioned room. Lethal concentrations (LC10 , LC50 and LC90 ) were determined after 48â h. After assessing the larvicidal potential of essential oils, molecular docking was carried out to study protein-ligand interactions and their propensity to bind to insect enzyme sites (AChE). The essential oil of O. gratissimum was the most effective with the lowest lethal concentrations (LC10 =0.91 %, LC50 =1.91 % and LC90 =3.92 %). The least toxic oil to larvae was Citrus sp. (LC10 =5.44 %, LC50 =20.50 % and LC90 =77.41 %). Molecular docking revealed that p-cymene and thymol from O. gratissimum essential oil are structurally similar and bind to the AChE active site via predominantly hydrophobic interactions and a H-bond with Tyr374 in the case of thymol. The essential oil of O. gratissimum constitutes a potential candidate for the development of biological insecticides for the fight against insect pests and for the protection of the environment.
Asunto(s)
Insecticidas , Ocimum , Aceites Volátiles , Animales , Aceites Volátiles/farmacología , Aceites Volátiles/química , Spodoptera , Aceites de Plantas/química , Simulación del Acoplamiento Molecular , Timol/farmacología , Côte d'Ivoire , Ocimum/química , Insecticidas/farmacología , LarvaRESUMEN
The abusive and repeated use of synthetic chemical insecticides has proven to be harmful to human health and the viability of the cotton production system in Ivory Coast, so it is imperative to find alternatives. . Thus, the objective of this study was to study the chemical composition and biological activity of essential oils of Lippia multiflora (Verbenaceae) and Eucalyptus globulus (Myrtaceae) and to evaluate their insecticidal potential in the laboratory on three main pests of cotton. After essential oils extraction, their chemical composition was determined. Also, antioxidant activity and cholinesterase inhibitor of essential oils were evaluated. After that, different concentrations of the two essential oils were prepared and applied by contact on groups of insects constituted by ten. The essential oil of L.â multiflora was the most toxic for the three pests tested. Indeed, the lethal concentrations (LC50 ) were 1.74 %, 1.39 and 7.20 %, respectively, on Pectinophora gossypiella, Thaumatotibia leucotreta and Helicoverpa armigera. In contrast, the values obtained with E.â globulus essential oil were nine to two times greater (16.05 %, 10.23 % and 16.32 %, respectively on these pests). With respect to the chemical composition of the essential oils, E.â globulus essential oil was the richest in oxygenated monoterpenes (65 %) with 1,8-cineole or eucalyptol as the majority compound (61.6 %). The essential oil of L.â multiflora was distinguished by a lower proportion of oxygenated monoterpenes (44.3 %), but it contained more terpene elements (24 vs. 15 for the essential oil of E.â globulus). The essential oils of L.â multiflora and E.â globulus also showed significant inhibition of acetyl (2.13 and 2.16â mg galantamine equivalent (GALAE)/g, respectively) and butyryl cholinesterase (4.03 and 3.61â mg GALAE, respectively). L.â multiflora was differentiated by its good inactivation of tyrosinases (163.46 versus 58.95â mg kojic acid equivalent (KAE)/g in E.â globulus). Better antioxidant activity was observed with L.â multiflora essential oil relative to DPPH (7.05±0.34â mg trolox equivalent (TE)/g). Biopesticides based on L.â multiflora essential oil could be developed for the phytosanitary protection of cotton plant.
Asunto(s)
Eucalyptus , Insecticidas , Lippia , Aceites Volátiles , Animales , Antioxidantes/farmacología , Inhibidores de la Colinesterasa/farmacología , Côte d'Ivoire , Eucaliptol , Eucalyptus/química , Gossypium , Humanos , Insecticidas/química , Insecticidas/farmacología , Lippia/química , Monoterpenos/química , Aceites Volátiles/química , Aceites Volátiles/farmacología , Aceites de Plantas/químicaRESUMEN
In recent years, in all cotton production areas in Ivory Coast, whitefly (Bemisia tabaci) and jassid (Jacobiella facialis), two biting sucker insects were causing depreciation of quality of the cottonseed and fiber obtained at harvest. However, the excessive use of synthetic chemical insecticides against these pests presents a danger for the sustainability of the production system. This study aims to evaluate the insecticidal efficacy of essential oils of Ocimum gratissimum and Cymbopogon citratus on B.â tabaci and J.â fascialis and on the technological parameters of the cottonseed and fiber. A field experiment was conducted in which essential oils of O.â gratissimum and C.â citratus were applied to cotton plants every two weeks from day 45 to 115 after emergence using a backpack sprayer. The effects of these extracts were compared to those of a synthetic chemical insecticide composed of acetamiprid and alphacypermethrin known under the trade name IBIS A 52 EC (positive control). After 160â days of cultivation where entomological data were collected, the seed cotton samples were harvested, ginned and submitted for analysis. O.â gratissimum essential oil at concentrations of 1 and 5 % gave to the cotton plants better protection against whiteflies and jassids. In addition to the synthetic chemical, these cotton plants received a better proportion of healthy cottonseed, fat and a fiber with very good reflectivity. The essential oil of O.â gratissimum could therefore be integrated into the phytosanitary protection programs of the cotton plant.
Asunto(s)
Cymbopogon , Hemípteros , Ocimum , Aceites Volátiles , Animales , Côte d'Ivoire , Gossypium , Aceites Volátiles/farmacología , Aceites de Plantas/farmacologíaRESUMEN
Among the alternatives to environmentally toxic and socio-economically unacceptable chemical pesticides, essential oils from Ocimum gratissimum and Cymbopogon citratus were tested on the main pests and beneficial insects of the cotton plant in Côte d'Ivoire. After extraction and chemical analysis of the essential oils, field trials were carried out using a Fisher block system with three treatment repetitions where their effects compared with those of a registered synthetic insecticide (IBIS A 52 EC). Foliar applications of the products were carried out in accordance with the cotton plant protection extension programme in Côte d'Ivoire from the 45th to the 115thâ day after plant emergence, with one application every fortnight. Twenty-three and forty compounds representing about 96 and 99 % of the oil composition of O.â gratissimum and C.â citratus respectively were elucidated. The most abundant compounds were p-cymene and thymol (O.â gratissimum) and myrcene, neral and geranial (C.â citratus). The essential oil of O.â gratissimum at concentrations of 2 and 5 % showed insecticidal activity on all pests (biting-sucking and carpophagous), except the phyllophagous Syllepte derogata. C.â citratus, at a low concentration (1 %), was particularly toxic to whiteflies (Bemisia tabaci), however, it favoured the action of beneficial insects, specifically black ants and ladybirds in the cotton plots, unlike the chemical product. EO of O.â gratissimum (1.60 and 4.62â mg GALAE/g, respectively) and C.â citratus (2.26 and 2.78â mg GALAE, respectively) exhibited also significant acetyl and butyryl cholinesterase inhibitors. Insecticide formulations based on the essential oils of O.â gratissimum and C.â citratus offer favourable prospects for their use in cotton cultivation as an alternative to chemical pesticides.