Chemical composition and biological activities of selected exudate gums

Abstract

The selected exudate gums from medicinal plants, Kondagogu (Cochlospermum gossypium Dc.), Karaya (Sterculia urens Roxb.) and Acacia (Acacia senegal (Linn.) Willd.) were recognized in the term of polysaccharide dietary soluble fibers. The in vitro biological activities were performed namely glucose entrapment ability against dialysis; α- glucosidase, pancreatic lipase and tyrosinase inhibition effects using 1-Deoxynorjirimysin, Oristat and Ascorbic acid as positive control; disturbance on lipid’s solubility in synthetic bile salt and pig bile micelles; and DPPH scavenging effect compared to Butylated hydroxytoluene. The physical properties for viscosity and average molecular weight were investigated. The monosaccharide composition was analyzed qualitatively and quantitatively using gas chromatographic technique. Total protein contents were quantities by Lowry method. Only Kondagogu gum showed 39 % of glucose entrapment property against dialysis tubing. The exudate gums had no effect on α-glucosidase inhibition. The effect on cholesterol solubility in bile salt micelles showed that Kondagogu and Acacia gums had slightly inhibitory effects (16 and 23%). Kondagogu and Acacia gums inhibited 16 and 20 % of lipase activity. The lipase inhibitory effect was reciprocal relationship to the concentration of gum gels. Tyrosinase enhancing activity was shown among these gums. Kondagogu and Karaya gums expressed 10% and 20% DPPH scavenging effect respectively, while Acacia gum had no effect. The viscosity determined by falling ball viscometer was 574.1, 25.2 and 1.0 cP for Kondagogu, Karaya and Acacia gums respectively. The determination of average molecular weight performed by size exclusive chromatography using SEC-HPLC with refractive index detector revealed the average molecular weight more than 2,350 kDa for Acacia, Kondagogu and Karaya gums, indicating their large structures. Kondagogu gum was composed of galactose, rhamnose and galacturonic acid (14.6, 17.1 and 17.2 % by weight respectively). Karaya gum was composed of galactose, rhamnose, galacturonic acid and glucuronic acid (14.7, 8.9, 9.1 and 36.0 % by weight respectively). Acacia gum contained arabinose, galactose, rhamnose and glucuronic acid (21.4, 42.6, 10. 6 and 22.5 % by weight respectively). Total protein contents among these gums were 2.4, 9.5 and 4.7 % by weight respectively.