Studies on the structure of polysaccharides from the bark of Melia azadirachta

Water-soluble polysaccharides, designated as GIa and GIb, were isolated from the bark of Melia azadirachta (Meliaceae) and their inhibiting effect on subcutaneously inoculated Sarcoma-180 was tested. GIa and GIb each gave a single peak on ultracentrifugation and gel filtration. Methylation, periodate oxidation and 13C-NMR spectroscopic studies suggested that GIa is composed of the following repeating unit ; α-D-Glc 1→4α-D-Glc 1→4α-D-Glc 1→4α-D-Glc 1→4α-D-Glc 6←1α-L-Araf. GIb is a branched arabinofucoglucan, containing a main chain of (1→4)-linked α-D-glucopyranosyl units substituted in the 6 position with side chains of α-L-arabinofuranosyl units. 3-O-substituted fucopyranose is attached to the α-(1→4) glucose units at the 4 position in the main chain.