Biotransformation of benzaldehyde-type and acetophenone-type derivatives by Pharbitis nil hairy roots

The glucosylation of some coumarin and Havone derivatives on incubation with the hairy roots of morning glory (Pharbitis nd) was previously reported. We further studied the biotransformation of benzaldehyde- and acetophenone-type derivatives. Vanillin and isovanillin were reduced to alcoholic derivatives and glucosylated at the phenolic and the alcoholic hydroxyl groups. In the case of 3,4-dihydroxybenzaidehyde, the formyl group was reduced and the 3-hydroxyl or 4-hydroxyl groups were glucosylated to give monoglucosides. The 3-hydroxyl group was predominantly glucosylated to the 4-hydroxyl group. 4-beta-(D)-Glucopyranosyloxy-3-methoxybenzylalcohol was obtained in low yield. In time-course experiments with vanillin, it was found that the high-level reduction of the formyl group and glucosylation of the phenolic hydroxyl group occurred, and finally 4-O-beta-(D)-glucopyranosylvanillylalcohol was obtained as the main product. In the case of 3,4-dimethoxybenzaidehyde, 3,4,5trimethoxybenzaldehyde, and salicylaidehyde, the formyl groups were reduced, and then the hydroxyl groups at the benyl position were glucosylated to give alcoholic glucosides in relatively high yields. In 4-hydroxy-3methoxyacetophenone, the 4-hydroxyl group was glucosylated and two dimerized glucosides, biphenyl and biphenylether types, were obtained in low yields. In acetophenone, I-beta-(D)-glueopyranosyloxy-1-phenylethane and 2-beta-(D)-glueopyranosyloxyacetophenone were obtained. As mentioned above P nil hairy roots showed various biotransformative activities including glucosylation of phenolic and benzylic hydroxyl groups, reduction of the formyl group near the benzene ring, and phenol oxidation dimerization. The glucosylation reaction was especially interesting for the production of valuable glucosides.