Toxicity of 4,11-Selinnadien-3-one from Nutsedge (Cyperus rotundus L.) Tuber Extracts to Diamondback Moth Larvae (Plutella xylostella L.), Detoxification Mechanisms and Toxicity to Non Target Species

Abstract

Tubers of nutgrass (Cyperus rotundus L.) were collected from various locations of Thailand during the summer and rainy seasons. Toxicity against the diamondback moth (Plutella xylostella L.) was observed using different concentrations of the active compound, 4,11-selinnadien-3-one. The toxic effects were also determined on mice (Mus musculus), fish (Poecillia reticulata) and bee larvae (Apis florea). It was found that the active principle of nut grass was higher in summer than that in rainy season by ca. 2 folds. This active principle varied according to geographical vareas with Chanthaburi and Chaing Mai producing the highest amounts of 4,11-selinnadien-3-one (0.13-0.16% ai. yield) compared with the other. The LC₅₀ against 2^nd–3^rd instar larvae of diamondback moth were 7-12 ppm. Detoxification enzyme activities as well as synergistic effects revealed that monooxygenase, esterases and some degrees of glutathione-S-transferase played a role in detoxification. Furthermore, synergists, PB and TPP, could raise the effectiveness of the active principle up to ca. 2-6 fold. At 2,000 ppm of 4,11-selinnadien-3-one, exposed mice showed no sign of acute dermal, acute oral or eye irritation effects. However, the active principle was toxic to other non target organisms with LC₅₀ of 28.01 ppm and 10.8 ppm to 1-month old guppies and bee larvae, respectively.