Total Phenolic and Flavonoid Contents, Metabolic Profiling, and In Vitro and In Silico Antioxidant Studies of the Leaf and Stem Extracts of Acalypha fimbriata Schum. & Thonn. (Euphorbiaceae)

Abstract

In this study, phenolic and flavonoid contents of various extracts of Acalypha fimbriata Schum. & Thonn. leaf and stem were determined. The metabolic profile of one extract was studied using GC-MS analysis. The antioxidant activities of the extracts were evaluated using in vitro and in silico studies. Four extracts each of leaf and stem of A. fimbriata have phenolic contents of 0.17 - 0.29 and 0.15 - 0.29 mg gallic acid equivalent/g extract, respectively. The leaf extracts have flavonoid content of 0.13 - 0.40 mg quercetin equivalent (QE)/g extract, which was slightly higher than that of the stem (0.18 - 0.33 mg QE/g extract). Extracts of the stem (IC₅₀ range 50.82 - 62.94 μg/ml) showed greater DPPH radical scavenging activity than those of the leaves (IC₅₀ range 61.03 - 82.24 μg/ml). All the extracts (except the ethyl acetate and aqueous extracts of the leaf) demonstrated significant NO^• radical scavenging activities, which were comparable (p > 0.05) to that of ascorbic acid. The extracts of the leaf and stem displayed lower reducing powers (0.07 - 0.56 and 0.09 - 0.50, respectively) compared to ascorbic acid (0.16 - 0.63) and showed considerable total antioxidant capacity values of 0.27 - 0.55 and 0.36 - 0.54 mg ascorbic acid equivalent/g extract, respectively. Some metabolites, including preg-4-en-3-one-17α-hydroxyl-17β-cyano, salirepin hexaacetate, eugenol and squalene were identified in one of the extracts. These metabolites gave good binding affinities against cytochrome P450, lipoxygenase, myeloperoxidase, NADPH oxidase and xanthine oxidase, indicating good antioxidant potentials. This study reveals that extracts of A. fimbriata possess broad spectrum of antioxidant activity and could be exploited as sources of antioxidant constituents to manage oxidative stress.