Protective effects of polysaccharides from Psidium guajava leaves against oxidative stresses

The aim of this study was to analyze antioxidant properties of a polysaccharide isolated from Psidium guajava leaves (PS-PGL) in vitro including its radical scavenging activities and protective effects against damage to cells as well as in vivo in zebrafish. The water extract of P. guajava leaves (WE-PGL) and PS-PGL showed strong radical scavenging effects in terms of 2,2-diphenyl-1-picrylhydrazyl (DPPH), hydroxyl, and alkyl radical. Compared to WE-PGL, PS-PGL enhanced all scavenging activities and in particular strongly scavenged the hydroxyl radical (50% inhibitory concentration [IC50], 0.02mg/mL). In addition, PS-PGL exerted a protective effect against hydrogen peroxide-induced oxidative stress and against toxicity to Vero cells. Furthermore, in vivo experiments using zebrafish embryos indicated that treatment with hydrogen peroxide decreased the survival rate and heart-beating rate of zebrafish embryos, whereas these problems were reduced by PS-PGL treatment. Moreover, PS-PGL inhibited hydrogen peroxide-induced reactive oxygen species (ROS) production, lipid peroxidation, and cell death. Taken together, these results suggest that PS-PGL may be useful as a beneficial antioxidant material in the food and cosmetic industries.