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 ( 1 H, 13 C) and 2D NMR ( 1 H- 1 H 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 IC 50 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.