Insect growth inhibition, antifeedant and antifungal activity of compoundsisolated/derived from Zingiber officinale Roscoe (ginger) rhizomes

Fresh rhizomes of Zingiber officinale (ginger), when subjected to steam dis tillation, yielded ginger oil in which curcumene was found to be the major constituent. The thermally labile zingiberene-rich fraction was obtained fr om its diethyl ether extract. Column chromatography of ginger oleoresin fur nished a fraction from which [6]-gingerol was obtained by preparative TLC. Naturally occurring [6]-dehydroshogaol was synthesised following condensati on of dehydrozingerone with hexanal, whereas zingerone and 3-hydroxy-1-(4-h ydroxy-3-methoxyphenyl)butane were obtained by hydrogenation of dehydrozing erone with 10% Pd/C. The structures of the compounds were established by H- 1 NMR, C-13 NMR and mass (EI-MS and ES-MS) spectral analysis. The test comp ounds exhibited moderate insect growth regulatory (IGR) and antifeedant act ivity against Spilosoma obliqua, and significant antifungal activity agains t Rhizoctonia solani. Among the various compounds, [6]dehydroshogaol exhibi ted maximum IGR activity (EC50 3.55 mg ml(-1)) while dehydrozingerone impar ted maximum antifungal activity (EC50 86.49 mg litre(-1)). (C) 2001 Society of Chemical Industry.