LAUSR

BACKGROUND Lotus seedpods is the agricultural by-products of lotus (Nelumbo nucifera Gaertn.), which is widely cultivated in Southeast Asia and Australia. Most of lotus seedpods are considered wastes which are abandoned and incinerated, resulting in significant waste of resources and heavy environmental pollution. For recycling lotus seedpods, the extraction optimization, physicochemical properties, antioxidant activity and α-glucosidase inhibitory effect of the contained polysaccharides were firstly investigated in the present study. RESULTS Hot water extraction of lotus seedpod polysaccharides was optimized by using a response surface methodology combined with a Box-Behnken design, and the optimum conditions were as follows: a liquid-solid ratio of 25.0 mL g-1 , an extraction temperature of 98.0 °C, and an extraction time of 138.0 min. Under these conditions, an experimental yield of 5.88±0.06% was obtained. Physicochemical analyses suggested that lotus seedpod polysaccharides belong to acidic heteropolysaccharides and are principally composed of rhamnose, arabinose, galactose, glucose, mannose and galacturonic acid. The polysaccharide has a broad molecular weight distribution (2.15×105 to 1.77×107 Da), an α-configuration and mainly possesses smooth and sheet-like structures. Biological evaluations showed that the polysaccharide possessed good scavenging activity on 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt, 1,1-diphenyl-2-picryl-hydrozyl and hydroxyl radicals, and exerted obvious inhibitory effect on α-glucosidase activity. Moreover, the polysaccharide was determined to be a mixed-type noncompetitive inhibitor of α-glucosidase. CONCLUSION These results indicated that lotus seedpod polysaccharides have potentials as natural antioxidants and hypoglycaemic substitutes. This study provides the theoretical bases for the exploitation and application of polysaccharides from the by-product resources lotus seedpod. This article is protected by copyright. All rights reserved.