​Antioxidant Responses of Arsenite-induced Oxidative Stress in Rice (Oryza sativa L.) and its Modulation by Eugenol (Extracted from Ocimum sanctum)

Abstract

Background: Irrigation with arsenic-contaminated groundwater is leading to high arsenic-laden rice seeds and lower yields. In the present study, the effect of exogenous treatment of eugenol (extracted from Ocimum sanctum L. leaf) on hydroponically grown rice seedlings was examined by investigating the antioxidant system under arsenic stress. Methods: In the experiment 7 day old rice seedlings (IR-64) were exposed to 10,50,100 µM of arsenite separately and co-treatment with 10,50,100 µM eugenol in a hydroponic medium for 7 days. The activity of antioxidant enzymes such as superoxide dismutase, ascorbate peroxidase, glutathione peroxidase, catalase and lipid peroxidation (malondialdehyde) in root and shoot tissues were determined separately by standard protocol. Result: Under arsenic treatment oxidative stress was induced by overproduction of reactive oxygen species (ROS) and disruption of antioxidant defense system measured in terms of increased activity of antioxidant enzymes and lipid peroxidation (malondialdehyde) in root and shoot tissues separately. Eugenol-treated seedlings along with arsenic exposure substantially decreased the level of arsenic uptake in plants resulting in a substantial reduction in ROS overproduction and MDA content. SOD, CAT, GPX activities perform an influential role in arsenic stress acclimatization and eugenol treated seedlings with arsenic exposures indicated substantial changes in all variables evaluated as compared to arsenic treatment only. This study suggests that oxidative stress caused by arsenic was ameliorated by eugenol.