In Vitro Glucose Entrapment and Alpha-Glucosidase Inhibition of Mucilaginous Substances from Selected Thai Medicinal Plants

As a continuous searching for anti-diabetic(type II) substances, seven mucilage polysaccharides from selected plants were studied as follow: aerial parts of Basella alba Linn., fruits of Hibiscus esculentus Linn., leaves of Litsea glutinosa (Lour.) C.B. Robinson, seeds of Ocimum canum Sims., seeds of Plantago ovata Forssk., fruits of Scaphium scaphigerum G. Don. and seeds of Trigonella foenum-graecum Linn. The bioactive properties for entrapping glucose, inhibiting enzyme alpha-glucosidase and free radical scavenger were in vitro studied compared to glucomannan. The physical characteristics for water holding capacity and viscosity were determined. The chemical characteristics were assayed for monosaccharide composition using methanolysis, TMSderivatization and gas chromatography. O. canum mucilage superiorly entrapped glucose compared to glucomannan. This activity was relevant to its highly viscous gelation. S. scaphigerum showed another property of alphaglucosidase inhibition. S. scaphigerum mucilage (0.5%) inhibited the enzyme activity by 82.6%, compared to 1-Deoxynorjirimycin (by 47.6%). Most mucilages, except O. canum and P. ovata, showed DPPH scavenging activity higher than glucomannan. Galacturonic acid was found in 3 from 7 mucilages namely B. alba, P. ovata and S. scaphigerum. Whereas rhamnose was common sugar found in all seven mucilages. Monosaccharide components of these mucilages were compared to the results from the previous reports. 838 C. Palanuvej et al.: Sci Pharm. 2009; 77; 837–849.