The antioxidant activity, total phenolic and monomeric anthocyanin content of <em>Gymnema sylvestre</em> leaf aqueous extract

Abstract

The Gymnema sylvestre is a widely recognized medicinal plant, particularly for its effectiveness in treating diabetes. Aim of this study is to measure the antioxidant property, polyphenol and anthocyanin content of G. sylvestre aqueous extract using various in-vitro techniques. The aqueous extract was prepared and total phenolic compounds (TPC), DPPH (2,2-Diphenyl-1-Picrylhydrazyl) radical scavenging ability, total antioxidant activity using ferric reducing antioxidant power (FRAP), ferric reducing power and monomeric anthocyanin content were estimated. Correlation analyses were performed for TPC and anthocyanin against the antioxidant activity. The TPC was 4.55±0.34 mg g-1 of fresh leaf weight (FLW) and the IC50 value for DPPH radical scavenging ability was 2.40 mg mL-1 of leaf extract concentration. The percentage of inhibition strongly correlated (R2 = 0.99) with the concentration of the leaf extract. The total antioxidant power of the leaf extract was 21.06±1.74 μmol g-1 of FLW.The ferric-reducing power showed a positive correlation with the leaf concentration (R2 = 0.99). The anthocyanin content of the leaf extract was 167.84±1.45 mg per 100 g of leaf. The TPC and anthocyanin exhibited strong positive correlations with total antioxidants and DPPH, but a weak correlation with reducing power. The antioxidant properties of leaf extract could be ascribed to the presence of TPC and anthocyanin as it showed a strong correlation with antioxidant activity. This is the first study that reported the anthocyanin content of G. sylvestre leaf extract. This study found G. sylvestre leaf water extract has antioxidant properties and contains a significant amount of TPC and monomeric anthocyanin.