Characterisation and immuno-stimulating activity of polysaccharides from Thai medicinal plants

Water-soluble polysaccharides were isolated from the tubers of Butea superba Roxb. and Pueraria candollei Wall. Ex Benth. var. mirifica (Shaw et Suvat.) C. Niyomdham, the leaves of Centella asiatica (L.) Urb, Ocimum basilicum L., Psidium guajava and Andrographis paniculata (Burn. f.) Nees, the stems of Cymbopogon citratus (Stapf ExG), and the fruits of Psidium guajava and Scaphium scaphigerum. The immunological impacts of the polysaccharides on T-lymphocyte proliferation in vitro was investigated by flow cytometric (immunofluorescence) analysis using staphylococcal enterotoxin B (SEB) as a positive control. It was found that the polysaccharides enhanced T-lymphocyte proliferation, ranging from 4.5 to 27.0% at a concentration of 100 mu g mL-1, while the activity of SEB was 13.3%. The medicinal plants showing the highest immuno-stimulating activity were the tubers of Butea superba Roxb. The water-extracted tubers contained 60.0% (w/w) carbohydrates with 6.6% (w/w) uronic acid. The major constituent monosaccharides of the tubers were 28.2 mol% galactose, 10.5 mol% arabinose and 36.4 mol% glucose.