Abstract
A benzophenone, maclurin-1, 3, 5-14C3 (3), was efficiently incorporated into C-glucosylxanthones [mangiferin (1) and isomangiferin (2)] of Anemarrhena asphodeloides without randomization, but the labelled aglycone of 1 and 2 (1, 3, 6, 7-tetrahydroxyxanthone-2, 4, 9a-14C3) (4) was essentially not incorporated. Furthermore, the incorporation of phenylalanine-3-14C into 1 and 2 was clearly suppressed by the addition of non-labelled maclurin (3) to the precursor solution. These results indicate that C-glucosylation of 1 and 2 occurs at the stage of maclurin (3), prior to the formation of the xanthone nucleus, and that 1 and 2 may be biosynthesized via 3-C-glucosylmaclurin (6). A biosynthetic route is proposed for mangiferin (1) and related C-glucosylxanthones.
