Effect of crude extracts and purified compounds of Alpinia galanga on nutritional physiology of a polyphagous lepidopteran pest, Spodoptera litura (Fabricius).

Secondary plant metabolites play an important role in providing protection to plants against herbivore insect pests. Keeping in view the increasing importance of biopesticides, the crude extracts from different plants are being investigated for insecticidal activities. Alpinia galanga, a medicinal plant belonging to family Zingiberaceae exhibits a wide range of biological activities. In the present study, crude extracts of A. galanga and its purified compounds i.e. 1'-acetoxychavicol acetate and galangin were evaluated for their effect on various nutritional parameters of Spodoptera litura (Fab.). All the extracts exhibited a significant influence on relative growth and consumption rates as well as efficiency of conversion of ingested and digested food. Ethyl acetate extract was found to be the most effective causing significant reduction in values of RGR, RCR, ECI and ECD of S. litura larvae in comparison to control larvae. The highest concentration of the ethyl acetate extract (2500 ppm) resulted in 44.95%, 10.99%, 38.08% and 37.04% decrease respectively in RGR, RCR, ECI and ECD in comparison to control. The purified compounds also showed inhibitory effects on various nutritional parameters. 1'-Acetoxychavicol acetate was found to be more effective in comparison to galangin.