EXTRACTION, PARTIAL CHARACTERIZATION, AND STUDIES OF SOME SPECTROSCOPIC PROPERTIES OF THE ANIONIC POLYSACCHARIDE FROM COLOCASIA-ANTIQUORUM

The natural anionic polysaccharide (Ps-A) isolated from arum (Colocasi a antiquorum) tubers contains 56% neutral sugars as galactose, mannose , rhamnose, and arabinose, and 40% anionic components as galacturonic acid and mannuronic acid. The equivalent weight of Ps-A estimated by c onductometric and spectrophotometric titrations is rather high, 1510 /- 5, which on saponification is reduced to 479. This indicates that a bout two-thirds of the carboxylic groups of Ps-A exist in the esterifi ed form. Ps-A and its saponified product (Ps-B) induce strong metachro masia in the dyes 1,9-dimethyl methylene blue and pinacyanol chloride (PCYN). Ps-A, with its lower charge density, induces relatively sharp and single banded metachromatic spectra, but the spectra induced by Ps -B, with its higher charge density, is broad and multiple banded. Ps-A induces weak dichroism in PCYN, indicating a bit of helical asymmetry in its conformation; Ps-B does not induce dichroism in this dye. The failure of Ps-B to induce dichroism presumably indicates that Ps-B has a nonhelical conformation.