Preparation of lacquer polysaccharide sulfates and their antioxidant activity in vitro

Lacquer polysaccharide (LP) was isolated and purified from the sap of the lac tree (Rhus vernicifera). Five sulfated lacquer polysaccharide (LPS), with various molecular weights (Mw) and degrees of sulfation (DS) were prepared by the reaction of LP with sulfur trioxide–pyridine complex (SO3·Py) in DMSO. The structure of LPS was analyzed by GPC, UV–vis, FT-IR and 13C NMR spectroscopy; the Mw of LPS was in the range of 0.78–1.58 × 104, DS varied from 0.22 to 0.58, and unsaturated bond presence was observed by FT-IR. Antioxidant assays showed that LPS antioxidant activities were related to Mw, DS and unsaturated bond presence. One LPS, with moderate Mw and DS, showed the best antioxidant capacities, its reducing capacity was 0.61 at 500 μg/mL, scavenging ability for superoxide and hydroxyl radical were 56.4% at 500 μg/mL, 55.6% at 1000 μg/mL, respectively. The data obtained in in vitro models establish the antioxidant potential of LPS for application in pharmaceuticals. The LPS may be a promising antioxidant in vitro.