New phenolic compounds fromCalothamnus quadrifidusR.Br. aerial parts and their antioxidant activity

Two new compounds calothphenone (1) and 6-methoxy kaempferol 3-O-(6 ''-E-p-coumaroyl)-beta-d-glucopyranoside (6-methoxy tiliroside) (2) along with six known compounds viz gallic acid (3), methyl gallate (4), kaempferol 3-O-(6 ''-E-p-coumaroyl)-beta-d-glucopyranoside (tiliroside) (5), castalagin (6), kaempferol (7) and quercetin (8) were isolated from the ethyl acetate fraction (EAF) of 80% aqueous methanol extract ofCalothamnus quadrifidusaerial parts. Their structure was established based on different chemical and spectroscopic techniques (H-1-/C-13-NMR and 2D NMR). Antioxidant activity for EAF and compounds1,2and5was evaluated using DPPH, superoxide radical and nitric oxide (NO) inhibition methods. EAF exhibited strong activity to inhibit DPPH, superoxide and NO radicals. Moreover, all tested compounds demonstrated a close high ability to inhibit superoxide and NO radicals in comparison to ascorbic acid, but they exerted lower activity towards DPPH radical.