Studies on the constituents of Iris florentina L. II. C-Glucosides of xanthones and flavones from the leaves.

Four C-glucosylxanthones [Mangiferin (3), isomangiferin (2), 4 and 5] and three C-glucosylflavones [swertisin (6), isoswertisin (7) and isoswertiajaponin (8)] were isolated from the fresh leaves of Iris florentina L. (Iridaceae). The structures of 4 and 5 were shown to be 7-O-methylmangiferin and 7-O-methylisomangiferin, respectively, by chemical and spectroscopic methods. In addition, the 13C nuclear magnetic resonance chemical shifts of aryl carbons in these C-glucosylxanthones (2-5) were assigned. On the basis of the co-occurrence of several types of xanthone and flavone C-glucosides, the biosynthetic relationship between both C-glucosides is briefly discussed.