Evaluation of the antioxidant activity of extracts and flavonoids obtained from Bunium alpinum Waldst. & Kit. (Apiaceae) and Tamarix gallica L. (Tamaricaceae)

The aim of the present work was to evaluate the antioxidant activity of extracts and four flavonoids that had been isolated from the aerial parts of Bunium alpinum Waldst. et Kit. (Apiaceae) and Tamarix gallica L. (Tamaricaceae). In this work, the four flavonoids were first extracted via various solvents, then purified through column chromatography (CC) and thin layer chromatography (TLC). The four compounds were subsequently identified by spectroscopic methods, including: UV, mass spectrum ¹H NMR and ¹³C NMR. The EtOAc extract of Bunium alpinum Waldst. et Kit yielded quercetin-3-O-β-glucoside (3’,4’,5,7-Tetrahydroxyflavone-3-β-D-glucopyranoside) (1), while the EtOAc and n-BuOH extracts of Tamarix gallica L. afforded 3,5,3’-trihydroxy-7,4’-dimethoxyflavone (2), 3,5,7-trihydroxy-4’-methoxyflavone (3) and 5-hydroxy-3,7,4’-trimethoxyflavone (4). The antioxidant activity of the extracts and the flavonoids were then evaluated through DPPH free radical-scavenging assay. Of all studied extracts, the n-Butanol extract of Bunium alpinum (EC₅₀ = 1.84 μg/ml) showed the best antioxidant activity against (DPPH). In contrast, the isolates demonstrated varying degrees of antioxidant activity: compound (1) was the more active (EC₅₀ = 0.28 μg/ml), followed by compound (3) and (2) (EC₅₀ = 0.309μg/ml, EC₅₀ = 0.406 μg/ml, respectively), compound (4) showed the lowest activity. All the isolated flavonoids exhibited antioxidant activity, but this was lower than the control (Trolox). In conclusion, due to the presence of flavonoids in their ariel parts, the studied plants could be natural sources of several important antioxidant agents