Differential activity against aphid settling of flavones obtained from Clytostoma callistegioides (Bignoniaceae)

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).

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► Leaf extracts from Clytostoma callistegioides were found to have activity against aphid settling.
► A bioguided fractionation led to the isolation of three bioactive flavones.
► Galangustin exhibited the best anti-settling activity against aphids.