Chromotropic Behaviours of Chalta (Dillenia indica) Fruit Mucilage Polysaccharide towards some Cationic Dyes

Department of Chemistry, Maharaja Bir Bikram College, Agartala-799 004

Manuscript received 29 March 1994, revised 24 November 1994, accepted 6 February 1995

Chalta (Dillenia indica) fruit mucilage polysaccharide (DI) is an acid polysaccharide of low charge density (eq. wt. 996). Weak chromotropic ability of DI is reflected in its failure to induce metachromasia in methylene blue (MB). DI induces slight spectral shift in toluidine blue (TB) and distinct but multiple banded metachromasia in more metachromatic dye 1,9-dimethylmethylene blue (DMMB) at different polymer-to-dye concentrations (P/D). Blue-shift of principal absorption band (~110 nm) of pinacyanol chloride (PCYN) in its dilute aqueous solution (1.0 x 10^-5 M) in presence of DI at different P/D values, reflects stronger metachromatic potentiality of PCYN. Spectrum of aqueous solution of pseudoisocyanine chloride (PIC, 1.0 x 10^-5M) has been found to remain unperturbed by DI. Disruption of metachromatic compounds of PCYN-DI and DMMB-DI to the extent of -50% by -21% and -20% ethanol respectively, signifies lower stability of the systems.