Antioxidant activity of herb extracts from five medicinal plants from Lamiaceae, subfamily Lamioideae

Abstract

Five medicinal plants from the subfamily Lamioideae of the Lamiaceae were tested for antioxidant activity and screened for polyphenols content. Aerial parts of Ballota nigra, Lamium maculatum, Leonurus cardiaca, Marrubium vulgare, and Galeopsis tetrahit were extracted with methanol (MeOH) and subsequently partitioned by liquid-liquid extraction between petroleum ether (PE), dichloromethane (DCM), ethyl acetate (EA) and n-butanol (BuOH). All 25 extracts and subfractions were assayed for ^•DPPH and HO^• scavenging and phosphomolybdenum reduction. Total polyphenols and free hydroxycinnamic acids were determined by spectrophotometric assays. Predictably, all species possess remarkable antioxidant capacity, but the relative differences between species and fractions depended on the method of testing. The LLE method allows the partitioning of most active polyphenols into the polar solvents. The BuOH fraction of L. cardiaca had a lowest EC₅₀ for ^•DPPH scavenging - 4.45 µg/ml. The maximum inhibition of deoxyribose degradation of was demonstrated for B. nigra EA and BuOH fractions (79.32 ± 1.62% and 82.04 ± 2.28%, respectively). B . nigra EA, and L. cardiaca BuOH fractions had also the highest reducing capacity of 318.6 ± 14.7 mg/g and 271.4 ± 2.4 mg/g ascorbic acid equivalents. The studied plants can provide efficient antioxidant protection by complementary mechanisms, such as free radical scavenging and metal ions reduction. However, only polar fractions from L. cardiaca and B. nigra are the most potent.