Structural studies of a heteropolysaccharide (PS-I) isolated from hot water extract of fruits of Psidium guajava (Guava).

A water-soluble polysaccharide was isolated from hot aqueous extracts of fruits of Psidium guajava. The polysaccharide was found to contain 2-O-methyl-l-arabinose, 2-O-acetyl-D-galactose, and D-methyl galacturonate in a molar ratio of approximately 1:1:1. On the basis of acid hydrolysis, methylation analysis, periodate oxidation, and NMR studies ((1)H, (13)C, TOCSY, DQF-COSY, NOESY, ROESY, HMQC, and HMBC), the structure of the repeating unit of the polysaccharide was established as [carbohydrate structure: see text].