STUDY OF A POLYSACCHARIDE FROM THE STAMENS OF BOMBAX MALABARICUM FLOWERS

Abstract

A polysaccharide consisting of D–galactose, L–arabinose and L–rhamnose in the molecular ratio of 5:4:3 has been isolated from the dried stamens of the flowers of Bombax malabaricum. Hydrolysis of the completely methylated polysaccharide iyelded 2,3,4,6–tetra–0–methyl–D–galactose (1 mole),2,3,6–tri–0–methyl–D–galactose (1 mole), 2,3–di–0–methyl–D–galactose (3 moles), 2,3,4–tri–0–methyl–L–arabinose (2 moles), 2,4–di–0–methyl–L–arabinose (1 mole), 2–0–methyl–L–arabinose (1 mole), 2,3,4–tri–0–methyl–L–rhamnose (2 moles) and 3–0–methyl–L–rhamnose (1 mole). The end groups as determined by periodate oxidation method was found to be 43.95 per cent which is in close agreement to that revealed by methylation, 41.7 per cent. Partial acid hydrolysis followed by Chromatographie separation afforded (a) 3–β–L–arabinosyl–L–arabinose (I), (b) 4–β–galactosylgalactose (II), (c) 3–β–galactosyl–L–arabinose (III), (d) 6–α–L–rhmanosylgalactose (IV), (e) unidentified 0–α–L–arabinosyl (1 ← 2 or 4)–0–α–L–rhamnosyl (1 ( 6)–D–galactose (Va or Vb), (f) 6–β–galactosylgalactose (VI), (g) 6^2–β–galactosylgalatobiose (VII) and (h) 4^3–β–galactosylgalactotriose (VIII) besides the three neutral monosaccharides. The polysaccharide is highly branched and a most probable structure has been assigned to it showing the back–bone consisting of β–1:4–linked–D–galactopyranose and β–1:3–linked–L–arabinopyranose units with β–linked galactose and α–linked–L–rhamnose and L–arabinose units as end groups.