Abstract

Bioassay-guided fractionation of an ethanolic extract from aerial parts of Athrixia phylicoides using silica and sephadex column chromatography led to the isolation of three flavonoids. The compounds were identified as: 5-hydroxy-6,7,8,3’,4’,5’-hexamethoxyflavon-3-ol (1), 3-0-demethyldigicitrin (2), and Quecertin (3). Isolated compounds together with ethanol crude extract were tested for antioxidant activity using 2,2-diphenyl-1-picrylhydrazyl (DPPH)-spectrophotometric assay, while cytotoxicity effect was determined using XTT colorimetric assay. The crude extract showed a concentration-dependent radical scavenging activity with EC₅₀value of 10.64 ± 0.08 µg/ml. Compound 3 was the most potent radical scavenger, exhibiting EC₅₀ value of 1.27 ± 0.25 µg/ml, followed by compound 1 and 2 showing 2.74 ± 0.10 and 3.41 ± 0.09 µg/ml respectively. The crude extract showed no or little toxicity on Vero cells at lower concentrations tested exhibiting the IC₅₀ value of 107.8 ± 0.13 µg/ml. Compound 3 showed minimal toxicity effect by exhibiting IC₅₀ value of 81.38 ± 0.33 µg/ml as compared to compound 2 (IC₅₀, 28.92 ± 0.12 µg/ml) and compound 1 (IC₅₀, 27.91 ± 0.18 µg/ml). The results obtained from this study provide a clear rationale for the medicinal uses of A. phylicoides.

Key words: Athrixia phylicoides, antioxidant activity, cytotoxicity, 2,2-diphenyl-1-picrylhydrazyl, flavonoids, vero cells.