Anthraquinone rhamnosides from Cassia javanica root bark

Phytochemistry
1979.0

Abstract

Two anthraquinones and their glycosides have been isolated from the root bark of Cassia javanica. The aglycones were identified as emodin and 5-hydroxyemodin by mp, mmp, colour reactions and IR, UV, NMR and mass spectral data. These compounds have been reported from many plant sources [1, 2]. The other two pigments (1, 2) gave characteristic colour reactions of hydroxyanthraquinones and on acid hydrolysis, gave emodin and 5-hydroxyemodin respectively together with rhamnose. The attachment of the sugar moiety at position-8 in both cases was established by colour reactions [3] and UV spectra [4]. Both glycosides consumed 2 mol of periodate per mol liberating one mol of formic acid showing that the sugar is in the pyranose form. Hydrolysis of the glycosides by diastase indicated the α-nature of sugar linkage in both cases. On the basis of these results, the glycosides are 1.6-dihydroxy-3-methylanthraquinone 8-O-α-L-rhamnopyranoside (1) and 1,5,6-trihydroxy-3-methylanthraquinone 8-O-α-L-rhamnopyranoside (2). These glycosides have not been reported earlier from any plant source.

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