Structural features, antioxidant and acetylcholinesterase inhibitory activities of polysaccharides from stem of Physalis alkekengi L.

Abstract Physalis alkekengi L. ( P. alkekengi ) is an important medicinal plant in China. In this study, two polysaccharides (SPAP-1 and SPAP-2) were isolated from the stem of P. alkekengi using hot water extraction method. The extract was further purified by DEAE-cellulose and Sephadex G-200 chromatography. The chemical characteristics, surface features and thermal stability of SPAP-1 and SPAP-2 were evaluated. For the first time, high-performance liquid chromatography with refractive index detection and amino column (without sample derivatization) was performed to analyze the monosaccharide composition of polysaccharides obtained from the stem of P. alkekengi . As a result, SPAP-1 (Mw = 9.1 kDa) consisted of rhamnose, arabinose, galacturonic acid, mannose, and glucose in the ratio of 1.0:1.5:1.9:29.1:1.03, while SPAP-2 (Mw = 13.5 kDa) comprised of rhamnose, xylose, arabinose, mannose and glucose in the ratio of 31.8:14.8:1.0:6.5:22.6. Additionally, the antioxidant effects of SPAP-1 and SPAP-2 were evaluated by ferric reducing power, 2,2′-Azinobis-(3-ethylbenzthiazoline-6-sulphonate acid) (ABTS) and 2.2-Diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assays. The results showed that the purified polysaccharides exerted significant scavenging activities. Subsequently, acetylcholinesterase inhibitory effects in vitro of the polysaccharides were investigated, which showed that, SPAP-1 and SPAP-2 showed moderate acetylcholinesterase inhibitory activities. Thus, the polysaccharide content in P. alkekengi stem as promising source of natural products possess good antioxidant activities and may exert beneficial effects on cognitive function.