Antioxidant Activity of Extracts and Different Solvent Fractions of Glechoma hederacea L. and Orthosiphon stamineus (Benth.) Kudo

Background. Orthosiphon stamineus is a popular medicinal plant from tropical Asia consumed in the form of infusions. Glechoma hederacea, once popular as a medicinal plant and as a bitter beer supplement, is a ubiquitous weed growing wild in moderate climates of Eurasia. Both plants belong to the Nepetoideae subfamily and are rich in phenolic antioxidants such as rosmarinic acid and flavonoids. Antioxidant activity can contribute to their traditional uses in phytotherapy as well as to their preventive value in degenerative and life-style diseases.Objectives. Two medicinal Lamiaceae species were chosen to test their antioxidant potential using three complementary assays. Preliminary screening for total polyphenols and phenolic acids was also performed to find correlations with the activity. Fractionation of the crude extract was carried out to reveal the contributions of compounds of different polarity to total antioxidant status. Interspecific variation was also analyzed.Material and Methods. Aqueous methanol extracts were prepared by reflux extraction from Orthosiphonis folium and Glechomae herba. The extracts were fractionated using liquid-liquid extraction (LLE) with petroleum ether (PE), dichloromethane (DCM), ethyl acetate (EA), and n-butanol (BuOH). All extracts and fractions were studied for their antioxidant activity using spectrophotometric assays: DPPH scavenging, phosphomolybdenum reduction, and deoxyribose degradation assay. Polyphenol content was studied by the Folin-Ciocalteu method, Arnow reaction, and Lopez-Arnaldos assay.Results. Predictably, both species possess remarkable antioxidant capacity, but the relative differences between the species and fractions depended on the applied assay. Varying correlation of total polyphenol content and the amounts of various chemical classes of polyphenols was also observed depending on the mechanism of antioxidant testing. In O. stamineus, partitioning the crude extract led to distribution of the initially very high activity among the DCM, EA, and butanol fractions, whereas in G. hederacea the moderate activity of the methanol extract was greatly enhanced in the EA and butanol fractions, which were the strongest in all assays.Conclusions. These plants can provide efficient antioxidant protection by complementary mechanisms such as free radical scavenging and metal ion reduction. However, Orthosiphonis herba is more effective as an integral extract due to the synergistic action of its components, while Glechomae herba needs fortification by fractioning the crude extract into polar solvents to increase the proportion of rosmarinic acid, the most active agent in this herb (Adv Clin Exp Med 2008, 17, 6, 615-624).