Biotransformation of hydroxycoumarin derivatives by cultured suspension cells of Catharanthus roseus.

Using 7-hydroxy-4-methylcoumarin (1), 7-hydroxy-4-phenylcoumarin (2), 5,7-dihydroxy-4-methylcoumarin (3), 7,8-dihydroxycoumarin (4) as substrates, three new compounds, 4-methylcoumarin-7-O-beta-D-xylopyranosyl (1 --> 6) beta-D-glucopyranoside (1b), 4-phenylcoumarin-7-O-beta-D-glucopyranosyl (1 --> 6) beta-D-glucopyranoside (2b), 4-methylcoumarin-5,7-O-beta-D-diglucoside (3b), along with four known compounds (1a, 2a, 3a and 4a) were biosynthesized by the cell suspension cultures of Catharanthus roseus as biocatalyst. Their structures were elucidated by analysis of the physicochemical properties and 1H NMR, 13C NMR, HMBC and ESI-MS spectra. Besides, the results also showed that this novel biocatalyst system of C. roseus cell cultures has a great capacity of regio-selective glycosylation to the hydroxyl group of the exogenous substrates. Co-culture time curves on conversion were also established.