New antioxidant C-glycosyl flavone and flavonol derivatives from the Tunisian Achille acretica L.

Two new natural compounds, 2′,5′,5,6,7-pentamethoxyflavanol 1 and 3-C-β-D-glucopyranoside 7-O-methylapigenin 2, together with two known compounds, 4′,5,7-trimethoxyquercetin 3 and 6-methoxychroman 4 were isolated from the n-BuOH extract of Achillea cretica aerial parts. All the structures were identified by spectral analysis, 1D (1H, 13C) and 2D NMR (1H-1H COSY, NOESY, HSQC, HMBC) and ESI-MS as well as by comparing their spectroscopic data with those reported in the literature. The antioxidant activity of the isolated compounds was evaluated by DPPH and ABTS assays and the strucuture-activity relationship was discussed. All isolated compounds 1, 2, 3 and 4 showed a significant antioxidant activity. The compound 2 exhibited the highest antioxidant activity with IC50 values of 45.00 ± 2.00 μg/ml and 42.00 ± 1.00 μg/ml against the DPPH and the ABTS scavenging activity assay, respectively.