Available online at www.scholarsresearchlibrary.com Scholars Research Library Der Pharmacia Lettre, 2014, 6 (1):128-138 (http://scholarsresearchlibrary.com/archive.html) ISSN 0975-5071 USA CODEN: DPLEB4 128 Scholar Research Library Phytochemical screening and in vitro antioxidant activity of ethanolic extract of Homalomena aromatica (Araceae) root Chandana Choudury Barua 1 *, Anindita Talukdar 1 , Bhargavi Phukan 1 , Snigdha Hazarika 1 , Acheenta Gohain Barua 2 and Gakul Baishya 3 1 Department of Pharmacology & Toxicology, College of Veterinary Science, Khanapara, Guwahati, Assam 2 Department of Veterinary Public Health, College of Veterinary Science, Khanapara, Guwahati, Assam, India 3 Natural Products Chemistry Division, North East Institute of Science & Technology (NEIST), CSIR, Jorhat, Assam, India _____________________________________________________________________________________________ ABSTRACT Ethanolic extract of Homalomena aromatica root was selected to evaluate their in vitro antioxidant potential. Antioxidant potential of the plant part was estimated by different in vitro antioxidant assay procedures and their EC 50 values were calculated. Screening of phytochemical constituents and high performance thin layer chromatography and high performance liquid chromatography analysis of the ethanolic extract of H. aromatica were done for identification of some functional compounds in the plant. The ethanolic extract of H. aromatica exhibited maximum total antioxidant activity at 9 µg/ml and 20 µg/ml for all the seven models of free radical scavenging activity. At a concentration of 9 and 20 µg/ml of the plant extract, superior free radical scavenging activity was recorded. The extract showed the presence of phenolics and flavonoids; the reducing power of the extract increased linearly with concentration. The results of the present study showed that the crude ethanolic extract of H. aromatica contains high amount of phenolics and flavonoids which is also confirmed by HPTLC and HPLC analysis. In conclusion, the plant might be an alternative to the synthetic Antioxidants available in the market. Key words: Antioxidant activity, Homalomena aromatica, DPPH, FRAP, ABTS. _____________________________________________________________________________________________ INTRODUCTION In recent years, there is an increasing interest in the antioxidants. The main reason for this interest is the protection of cells, their organelles (especially membranes) and metabolic pathways against oxygen free radicals and their reactive derivatives (ROS) [1]. Natural antioxidants present in the plants scavenge harmful free radicals from our body. Free radical is any species capable of independent existence that contains one or more unpaired electrons which react with other molecules by taking or giving electrons, involved in many pathological conditions [2] and various physiological processes such as ageing, cancer, diabetes and atherosclerosis to name a few. Several studies have demonstrated that plant(s) produce potent antioxidants [3]. The most common reactive oxygen species (ROS) include superoxide (0 2- ) anion, hydrogen peroxide (H 2 0 2 ), peroxyl (ROO - ) radicals, and reactive hydroxyl (OH - ) radicals. The nitrogen derived free radicals are nitric oxide (NO) and peroxynitrite anion (ONOO) [4]. Under normal state of affairs, the ROS generated are detoxified by the antioxidants nearby in the body and there is symmetry between the ROS generated and the antioxidant present. However, due to ROS over production and/or derisory