Glycosylation of stilbene compounds by cultured plant cells

Abstract

Oxyresveratrol and gnetol are naturally occurring stilbene compounds, which have diverse pharmacological activities. The water-insolubility of these compounds limits their further pharmacological exploitation. The glycosylation of bioactive compounds can enhance their water-solubility, physicochemical stability, intestinal absorption, and biological half-life, and improve their bio- and pharmacological properties. Plant cell cultures are ideal systems for propagating rare plants and for studying the biosynthesis of secondary metabolites. Furthermore, the biotransformation of various organic compounds has been investigated as a target in the biotechnological application of plant cell culture systems. Cultured plant cells can glycosylate not only endogenous metabolic intermediates but also xenobiotics. In plants, glycosylation reaction acts for decreasing the toxicity of xenobiotics. There have been a few studies of glycosylation of exogenously administrated stilbene compounds at their 3- and 40-positions by cultured plant cells of Ipomoea batatas and Strophanthus gratus so far. However, little attention has been paid to the glycosylation of 20-hydroxy group of stilbene compounds by cultured plant cells. In this work, it is described that oxyresveratrol (3,5,20,40–tetrahydroxystilbene) was transformed to 3-, 20-, and 40-β-glucosides of oxyresveratrol by biotransformation with cultured Phytolacca americana cells. On the other hand, gnetol (3,5,20,60–tetrahydroxystilbene) was converted into 20-β-glucoside of gnetol by cultured P. americana cells. Oxyresveratrol 20-β-glucoside and gnetol 20-β-glucoside are two new compounds. This paper reports, for the first time, the glycosylation of stilbene compounds at their 20-position by cultured plant cells.