Insecticidal activity of indole derivatives against Plutella xylostella and selectivity to four non-target organisms.

The diamondback moth Plutella xylostella (Linnaeus, 1758) (Lepidoptera: Plutellidae) is a destructive pest of brassica crops of economic importance that have resistance to a range of insecticides. Indole derivates can exert diverse biological activities, and different effects may be obtained from small differences in their molecular structures. Indole is the parent substance of a large number of synthetic and natural compounds, such as plant and animal hormones. In the present study, we evaluate the insecticidal activity of 20 new synthesized indole derivatives against P. xylostella, and the selectivity of these derivatives against non-target hymenopteran beneficial arthropods: the pollinator Apis mellifera (Linnaeus, 1758) (Hymenoptera: Apidae), and the predators Polybia scutellaris (White, 1841), Polybia sericea (Olivier, 1791) and Polybia rejecta (Fabricius, 1798) (Hymenoptera: Vespidae). Bioassays were performed in the laboratory to determine the lethal and sublethal effects of the compounds on P. xylostella and to examine their selectivity to non-target organisms by topical application and foliar contact. The treatments consisted of two synthesized derivatives (most and least toxic), the positive control (deltamethrin) and the negative control (solvent). The synthesized compound 4e [1-(1H-indol-3-yl)hexan-1-one] showed high toxicity (via topical application and ingestion) and decreased the leaf consumption by P. xylostella, displaying a higher efficiency than the pyrethroid deltamethrin, widely used to control this pest. In addition, the synthesized indole derivatives were selective to the pollinator A. mellifera and the predators P. scutellaris, P. sericea and P. rejecta, none of which were affected by deltamethrin. Our results highlight the promising potential of the synthesized indole derivatives for the generation of new chemical compounds for P. xylostella management.

Synthesis, activity, and QSAR studies of tryptamine derivatives on third-instar larvae of Aedes aegypti Linn.

Special attention has been given to the mosquito Aedes aegypti Linn. (Diptera: Culicidae) owing to numerous dengue epidemic outbreaks worldwide. Failure to control vector spreading is accounted for unorganized urban growth and resistance to larvicides and insecticides. Therefore, researchers are currently searching for new and more efficient larvicides and insecticides to aid dengue control measures. Triptamine is known to affect insect behavior, development, and physiology. Expression of this compound in plants has reduced the growth rate of herbivore insects. In view of these facts, it was of our interest to synthesize triptamine amide derivatives as potential larvicides against Ae. aegypti, establishing a Structure-Activity Relationship. Eleven amide derivatives of triptamine were synthesized, characterized, and evaluated for their larvicidal activity against third-instar Ae. aegypti larvae. N-(2-(1H-indol-3-yl)ethyl)-2,2,2-trichloroacetamide exhibited the highest overall larvicidal potency, while N-(2-(1H-Indol-3-yl)ethyl) acetamide displayed the lowest larvicidal potency. A regression equation correlating the larvicidal activity with Log P was obtained. We have found a clear relationship between the larvicidal activity of non-chlorinated compounds and Log P. Analysis of the relationship between Log P and larvicidal activity against Ae. aegypti may be useful in the evaluation of potential larvicidal compounds.

Antinociceptive effect of the ethanolic extract of Amburana cearensis (Allemão) A.C. Sm., Fabaceae, in rodents / Efeito antinociceptivo do extrato etanólico de Amburana cearensis (Allemão) A.C. Sm., Fabaceae, em roedores

The ethanolic extract of the trunk bark of Amburana cearensis (EEA) was examined for its oral (p.o.) analgesic activity at the doses of 100, 200 and 400 mg/kg body weight. In the acetic acid-induced writhing test, the EEA (200 and 400 mg/kg, p.o.) reduced the number of writhing by 33.4 percent and 40.7 percent, respectively. Additionally, EEA (100, 200 and 400 mg/kg, p.o.) decreased by 77.5 percent, 79.7 and 91.3 percent, respectively, the paw liking time in the second phase of the formalin test. Therefore, EEA showed a dose-dependent analgesic effect in formalin test and was effective in reducing writhing in mice.

O extrato etanólico da entrecasca de A. cearensis (EEA) foi avaliado em modelos experimentais de nocicepção. No teste das contorções abdominais induzidas pelo ácido acético o EEA (200 e 400 mg/kg, v.o.) foi significativamente efetivo em inibir o estímulo álgico (33,4 por cento e 40,7 por cento), respectivamente, em relação aos animais do grupo controle. O EEA, em todas as doses, promoveu uma redução significativa do tempo de lambidas das patas na segunda fase do teste da formalina (77,5 por cento; 79,7 e 91,3 por cento). Os resultados sugerem uma ação antinociceptiva do EEA.