Antioxidant and Xanthine oxidase inhibitory activity of Euphorbia hirta extract using deep eutectic solvent

Abstract

The exposure to free radicals and gout cases have been a great concern today where the synthetic antioxidants and xanthine oxidase inhibitors have shown downsides in health effects that leads to the discovery of natural inhibitors from medicinal plants. Deep Eutectic Solvent (DES) have proved its ability as potent solvent in terms of economic impact and environmental impact compared to conventional solvents. DES were used to study for the extraction of natural xanthine oxidase inhibitors (XOI) and free radicals inhibitors from Euphorbia hirta which have proven to have high potential in replacing the synthetic antioxidants and synthetic XOI such as allopurinol. Choline chloride were used as the hydrogen bond acceptor while D-glucose were used as the hydrogen bond donor. The leaves pellet from Euphorbia hirta extract showed the highest inhibition (87.9552 ± 0.0061) % on free radicals assay and chosen to be used in other studies. The IC50 for free radicals inhibition of the gallic acid was (3.4779 ± 0.4736) μg/ml compared to the leaves pellet extract (10.5676 ± 0.5871) μg/ml. The IC50 value for xanthine oxidase inhibition of allopurinol was the lowest at (6.9413 ± 0.3244) μg/ml while the leaves pellet extract of Euphorbia hirta exhibited close value at (9.4084 ± 0.1330) μg/ml. The correlation value between the antioxidant effect and the xanthine oxidase inhibition of the leaves pellet extract proved to be 0.9608 which indicated there was strong relationship. From the Line-weaver Burk plot and solver function analysis, the mode of inhibition was non-competitive inhibition where the Km values of allopurinol and the leaves pellet extract remained at 11.6187 μM and 11.6182 μM respectively while the Vmax values of allopurinol and leaves pellet of Euphorbia hirta extract were found to be 0.0207 abs/min and 0.0503 abs/min.