Antioxidant capacity and phenol content of selected Algerian medicinal plants

Extracts from the bark of Fraxinus angustifolia as well as the leaves of Pistacia lentiscus and Clematis flammula have been investigated for their reducing power, inhibition of linoleic acid peroxidation and scavenging capacity on 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical and H2O2 using in vitro spectrophotometric methods. The results indicate that the best overall antioxidant capacity was shown by extracts of Pistacia lentiscus, followed by Fraxinus angustifolia and Clematis flammula. Pistacia lentiscus aqueous fraction obtained from chloroform partition showed a high and dose-dependant reducing power (IC50 = 50.03 mu g/ml), a very high scavenging ability against DPPH radical (IC50 = 4.24 mu g/ml) and an outstanding activity against linoleic acid peroxidation (IC50 = 0.82 mu g/ml). Fraxinus angustifolia aqueous fraction issued from chloroform extraction also exhibited a high DPPH scavenging activity (IC50 = 10.0 mu g/ml) and a high activity against linoleic acid peroxidation (IC50=5.06 mu g/ml). In contrast, it is the organic (chloroform) fraction of Clematis flammula that showed a high activity against linoleic acid peroxidation (IC50 4.6 mu g/ml), whereas the aqueous fraction of chloroform partition showed a moderate scavenging activity against DPPH (IC50 = 25.02 mu g/ml). The IC50 values for the antioxidant of reference, butylated hydroxyanisole (BHA) are 5.19, 6.16 and 71.16 mu g/ml for inhibition of linoleic acid peroxidation, DPPH scavenging activity and reducing power, respectively. With the exception of Pistacia lentiscus aqueous extracts obtained from hexane and chloroform partitions that showed high H2O2 scavenging ability, all the extracts from Fraxinus angustifolia and Clematis flammula showed only moderate and even weak capacity, respectively. The observed results which correlate positively with total phenol content strongly plead in favour of the use of these plants as potential food additives in replacement of synthetic compounds. (C) 2008 Elsevier Ltd. All rights reserved.