Structural Characterization of an Exopolysaccharide Isolated from Enterococcus faecalis , and Study on its Antioxidant Activity, and Cytotoxicity Against HeLa Cells

An exopolysaccharide (EPS-I) having the molecular weight ~ 2.6 × 105 Da, was isolated from a Zinc resistant strain of Enterococcus faecalis from costal area. The exopolysaccharide consists of D-mannose, D-glucose, and L-fucose in molar ratio of 9:4:1. The monosaccharide units in the EPS-1 were determined through chemical (total acid hydrolysis and methylation analysis) and spectroscopic (FTIR and 1H NMR experiment) analysis. The mannose-rich EPS-1 showed total antioxidant activity (1 mg mL−1 of EPS-I as functional as approximately to 500 ± 5.2 µM of ascorbic acid) and Fe2+ metal ion chelation activity (EC50 = 405.6 µg mL−1) and hydroxyl radical scavenging activity (EC50 = 219.5 µg mL−1). The in vitro cytotoxicity experiment of EPS-I against cervical carcinoma cell line, HeLa cells showed strong cytotoxic effect (LC50 = 267.3 µg mL−1) and at that concentration, it found almost nontoxic against normal healthy cells (HEK-293).