抄録
A new xanthone C-glycoside, named homomangiferin, C19H17O10 (OCH3)·1.5H2O, decomposing over 250° without melting, [α]14D+8.7° (pyridine), was isolated from crude mangiferin obtained from the bark of Mangifera indica L. On the basis of chemical and spectral data, it has been formulated as 2-C-β-D-glucopyranosyl-3-methoxy-1, 6, 7-trihydroxyxanthone (II), i.e., 3-O-methylmangiferin. Of four possible monomethyl ethers in the aglycone moiety of mangiferin (I), the three, 1-, 3- and 7-methyl ethers, have been synthesized and the identity of homomangiferin with synthetic 3-O-methylmangiferin was confirmed by direct comparison. The nuclear magnetic resonance spectra of natural and synthetic II and of the heptaacetate (III) measured in pyridine solution showed the signals of methoxyl and acetoxyl groups as a doublet at room temperature (20-23°) and as a sharp singlet at 50°, whereas the methoxyl signals of 1-O- and 7-O-methylmangiferins (VII, XI) and of swertisin (6-C-β-D-glucopyranosyl-7-methoxy-4', 5-dihydroxyflavone) (XIV) appeared as a sharp singlet.
