ß-Glucosidase involvement in the bioactivation of glycosyl conjugates in plants: synthesis and metabolism of four glycosidic bond conjugates in vitro and in vivo.

Mobile glucose-pesticide conjugates in the phloem are often restricted by decreases in biological activity. However, plants can bioactivate endogenous glucosides, which are assumed as able to bioactivate exogenous conjugates. In this study, four glycosidic bonds (O-, S-, N-, and C-glycosidic bonds) of glucose-pesticide conjugates were designed and synthesized, and then metabolism assays were carried out in vitro and in vivo. Results showed that ß-glucosidases played a role in the hydrolysis of O-glycosidic bond conjugates in Ricinus communis L. The liberated aglycons possessed insecticidal activities against Plutella xylostella L. and Spodoptera litura F. These results could help establish methods of circumventing the mutual exclusivity of phloem mobility and biological activity by hydrolyzing endogenous ß-glucosidases.

Synthesis of rotenone-O-monosaccharide derivatives and their phloem mobility.

Six monosaccharide derivatives of rotenone were designed and synthesized to assess whether rotenone could become phloem mobile by the addition of a monosaccharide group. Phloem mobility experiments showed that only D-glucose conjugates exhibit phloem transport properties in castor bean (Ricinus communis L.) seedlings. Two D-glucose conjugates, 2-O-ß-D-glucopyranosyldemethylrotenone and 6'-O-ß-D-glucopyranosyldalpanol, had significantly obtained systemicity compared with that of rotenone, and 6'-O-ß-D-glucopyranosyldalpanol was more mobile than 2-O-ß-D-glucopyranosyldemethylrotenone. Coupling with a monosaccharide core is a reasonable method for conferring phloem mobility on insecticides, but phloem mobility is also affected by the parent molecule and the position of the monosaccharide.