Journal of Medicinal Plants Research Vol. 4(20), pp. 2164-2172, 18 October, 2010 Available online at http://www.academicjournals.org/JMPR ISSN 1996-0875 ©2010 Academic Journals Full Length Research Paper Determination of in vitro antioxidant activities of different extracts of Marrubium parviflorum Fish et Mey. and Lamium amplexicaule L. from South east of Turkey Onder Yumrutas* and Saadet Demirors Saygideger 1 Department of Biology, Faculty of Art and Science, Gaziantep University, 27310, Gaziantep, Turkey. Accepted 19 August, 2010 This study was designed to determine the in vitro antioxidant activities of methanol and hexane extracts of Marrubium parviflorum Fish et Mey. and Lamium amplexicaule L. from Lamiaceae and their total phenolics, flavonoids, flavonols and phenolic acid content. The extracts were screened for their possible antioxidant potentials by -carotene/linoleic acid, 2,2-diphenyl-1-picrylhydrazyl (DPPH) and ABTS, power reducing, metal chelating and DNA nicking assays. The methanol extracts of these plants exhibited significant antioxidant activities determined by different these assays and contained significant levels of phenolics. Total phenolic content were determined by Folin-Ciocalteu assay. Phenolic contents of the methanol extracts were found 332.93 ± 26.90 and 183.36 ± 14.78 mg GAE/g dry weight, respectively. The amounts of phenolic acids in the extracts were characterized by a reverse- phase High Performance Liquid Chromatography (HPLC) method that used in the gradient elution employing diode array detection. The most abundant phenolic acid detected by HPLC-DAD in the methanol extracts was rosmarinic acid in M. parviflorum whereas valinic acid was observed in the methanol extract of L. amplexicaule. This study shows that methanol extracts of the plants have higher activities than their hexane extract, except DNA protecting activity (p < 0.05). Key words: Marrubium parviflorum, Lamium amplexicaule, antioxidant activity, phenolics, high performance liquid chromatography. INTRODUCTION Today, many scientists emphasize the harmful effects of free radicals (Asadi et al., 2010; Vichapong et al., 2010). Especially, role of oxygen radicals has been implicated in several diseases, including cancer, diabetes and cardiovascular diseases, ageing (Halliwell and Gutteridge, 1999). In addition, these molecules are considered to induce lipid peroxidation causing the deterioration of foods (Duthie, 1993). Antioxidants scavenge reactive free radicals and protect food and living systems from peroxidative damage, thus have health-promoting effects (Biglari et al., 2008). Moreover, edible plants are primary source of natural antioxidants. Polyphenols are important to dietary of humans and they *Corresponding author. E-mail: yumrutasonder@gmail.com. Tel: + 90-342-317 1927. Fax: + 90-342-317 1039. are available in fruit and vegetable (Vayalil, 2002). Phenolic compounds are known to exhibit a range of biological activities, including antibacterial, antioxidant and antiinflammatory properties (Kamatou et al., 2010; Samec et al., 2010). The antioxidant activities of phenolics are mainly due to their redox properties that allow them to act as a reducing agents and hydrogen donors (Rice-Evans et al., 1996). Plants contain high amounts of the phenolic compounds. The Lamiaceae includes a large number of plants and the plants are well worked in terms of antioxidant activities (Barros et al., 2010). Marrubium parviflorum and Lamium amplexicaule belong to the Lamiaceae. As far as our survey, there are no detailed reports in literature on antioxidant activities and phenolic compounds of M. parviflorum and L. amplexicaule. Thus, the aim of the study was to investigate the antioxidant potentials of the methanol and hexane extracts obtained from M. parviflorum and