Azam Mikani - Department of Entomology, Faculty of Agriculture, Tarbiat Modares University, Tehran, Iran.

Efficacy of quercetin on α-amylase, lipase and protease activities via crustacean cardioactive peptide (CCAP) content of the midgut of the diamondback moth, Plutella xylostella (L.) was investigated. Fresh cabbage leaf discs were dipped in quercetin solution at different concentrations (۱۰۰, ۵۰۰ and ۱۰۰۰ppm) for ۱۰ seconds. Third instar larvae of P. xylostella were fed on leaf dipped in quercetin solutions for ۵ days. α-Amylase, lipase and protease activities were evaluated for ۵ days. Quercetin significantly decreased lipase, protease and α-amylase activities in the midgut. The results of competitive ELISA showed that different concentration of quercetin had no effect on short neuropeptide F, tachykinin-۴ and allatostatin content of the midgut, but it was shown that quercetin (۵۰۰ and ۱۰۰۰ppm) decreased CCAP content of the midgut. Moreover, incubation of dissected midgut with CCAP increased α-amylase, lipase and protease activities. The injection of CCAP into the hemocoel clearly increased α-amylase, lipase and protease activities. Here, for the first time, it was confirmed that feeding on leaf dipped in quercetin, decreases CCAP content in the midgut of P. xylostella, that itself led to decrease of α-amylase, protease and lipase activities.

Plutella xylostella, Quercetin, Crustacean cardioactive peptide, α-Amylase, Protease