Studies on the Constituents of Iris florentina L.I. Isolation of C-Glucosylxanthones from the Underground Parts and Their Biosynthesis

Abstract

Three C-glucosylxanthones, 1-hydroxy-3, 5, 6-trimethoxyxanthone-2-C-glucoside (8), 1, 3, 5, 6-tetrahydroxyxanthone-2-C-glucoside (9) and isomangiferin (10), were isolated from the underground parts of Iris florentina L., besides mangiferin (2) and irisxanthone (3) which have been known as the components of this plant. In order to study the biosynthesis of 9 and 3, maclurin-(carbonyl-¹⁴C) (11) was fed to I. florentina L. Labelled 11 was efficiently incorporated not only into 2 but also 9 and 3, and the radioactivity in 9 was largely localized in the aglycone moiety. These results indicate that 11 was incorporated into 9 without randomization and that 9 and 3, therefore, were biosynthesized via C-glucosylation of maclurin (11). In addition to C-glucosylxanthones, two acetophenones, piceol (6) and acetovanillone (7), were isolated together with sinapic acid and protocatechuic acid.