This study was conducted to determine the total flavonoid and flavonol contents and the estimation of antioxidant activity by DPPH radical scavenging effect of crude ethanolic extracts of the aerial parts of four Algerian medicinal and aromatic plants : Juniperus oxycedrus L., Juniperus phoenicea L. (Cupressaceae), Cedrus atlantica Manetti (Pinaceae) and Marrubium vulgare L. ( Lamiaceae). Total flavonoid and flavonol contents in these extracts were determined using AlCl3 method and their amount calculated as quercetin μEQ/mg. Synthetic antioxidants such as rutin and BHA were used as standard. The results of antioxidant activity by DPPH radical scavenging indicated better activities for Cedrus atlantica Manetti and Marrubium vulgare L. (IC50 = 8.9 and 20.3 μg/ml respectively) than J. phoenicea L. and J. oxycedrus L (IC50 = 403.8 and 481.3 μg/ml respectively) by comparison with the standards rutin and BHA (IC50 = 1.38 and 1.87 μg/ml respectively). The results of the total flavonoid contents by AlCl3 method showed that all these species contained relatively low amounts of flavonoids and that J. oxycedrus had a better content than C. atlantica, J. phoenicea and M. vulgare (23.1, 16.8, 13.9 and 5.0 μgEQ/mg respectively) . The results the total flavonols are in the following order J. oxycedrus > M. vulgare > J. phoenicea > C. atlantica. (32.1, 23.6, 18.1 and 14.1 μgEQ/mg respectively).
