Exploration of an arabinogalactan isolated from Odina wodier Roxb.: Physicochemical, compositional characterisations and functional attributes

Exudate gum polysaccharides have a diverse range of functionalities in food, cosmetics, textiles, biomedical, pharmaceutical and other industries for centuries. The potentiality of gum odina as tablet binder, coacervates (chitosan-gum odina complex) for colon-targeted drug delivery system and also as prebiotic with immunomodulating properties was reported earlier. Since no detail study of the physicochemical, functional properties of the gum has been reported, the present investigation deals with physicochemical, compositional and functional characterisations of purified gum odina (PGO) for adopting in food and pharmaceutical industry. PGO, an arabinogalactan, was obtained by ethanol precipitation from exudates (gum odina) of tropical deciduous plant Odina wodier Roxb. Colour profiling of PGO including L* (87.74 +/- 0.42), a* (1.73 +/- 0.65) and b* (7.79 +/- 0.58) was determined. Physicochemical parameters revealed good flow ability and compressibility desired for an excipient. Concentration-dependent surface tension was measured by du Nouy ring method. Rheological study showed pseudoplastic behaviour of PGO dispersion. Sugar analysis by gas liquid chromatography indicated presence of arabinogalactan in PGO. Size exclusion chromatography of PGO revealed two high-molecular-weight components PGO-I (95%, Arabinose:Galactose :: 1:1.6) and PGO-II (5%, Arabinose:Galactose :: 1:4). Further characterisations of PGO by means of CHNS, FTIR, differential scanning calorimetry, X-ray diffraction, transmission electron microscopy, scanning electron microscopy and energy-dispersive X-ray diffraction, conductivity, pH, zeta potential analysis and antioxidant activity indicated typical polysaccharide characteristics. Collectively, this work established the fundamental properties of PGO and the results presented here will facilitate the applications of PGO as sustainable food additive, pharmaceutical excipient for commercial adoption.