Chemical composition and antioxidant activity of extracts from Daphne gnidium L.

Members of the Daphne genus have been of interest owing to their excellent medicinal value. In this work, we describe the results of phytochemical analysis and the antioxidant activity of the methanol extracts from leaves and stems of D. gnidium L. grown wild in Sardinia, Italy. Four coumarins (daphnetin, daphnin, acetylumbelliferon, and daphnoretin), nine flavonoids (apigenin, luteolin, quercetin, orientin, isoorientin, luteolin 7-O-glucoside, apigenin 7-O-glucoside, genkwanin, and 5-O-beta-primeverosyl genkwanine), and alpha-tocopherol were isolated. We investigated the ability of the two extracts and five pure compounds (daphnetin, daphnoretin, apigenin, luteolin, and cc-tocopherol) to protect linoleic acid against free radical attack in simple in vitro systems by autoxidation and iron- or EDTA-mediated oxidation. Pure compounds were the most active antioxidants. During autoxidation, daphnetin, luteolin, and alpha-tocopherol were effective at a molar ratio of 1:1600, 1:2500, and 1:2000, respectively. Daphnoretin was active only at high concentrations. During the iron-catalyzed oxidation of linoleic acid, all the materials tested showed activity in the following order: luteolin > daphnetin > alpha-tocopherol > leaf extract > stem extract > daphnoretin. Apigenin was not active in any of the experimental systems used.