MEDICINAL PLANTS ANTIOXIDANT AND RADICAL SCAVENGING PROPERTIES OF Iris germanica H. Nadaroðlu, 1 Y. Demir, 2 and N. Demir 3* Published in Khimiko-Farmatsevticheskii Zhurnal, Vol. 41, No. 8, pp. 13 – 18, August, 2007. Original article submitted November 20, 2006. The antioxidant activity of aqueous and ethanol extracts of iris (Iris germanica L., family Iridaceae) has been evaluated in vitro using various antioxidant assays, including reducing power, free radical scavenging, supe- roxide anion radical scavenging, hydrogen peroxide scavenging, and metal chelating activities. Both aqueous and ethanol extracts exhibit strong total antioxidant activity, showing 95.9, 88.4, 79.9% and 90.5, 78.0, 65.3% inhibition on peroxidation of linoleic acid emulsion in concentrations of 10, 30, and 50 mg/ml, respectively. Both extracts also possess effective reducing power and exhibit free radical scavenging, superoxide anion ra- dical scavenging, hydrogen peroxide scavenging, and metal chelating activities in concentrations of 20, 40, and 60 mg/ml. The antioxidant properties were compared to those of reference antioxidants (BHA, BHT, and a-tocopherol). In addition, the total content of phenolic compounds in both aqueous and ethanol iris extracts has been determined as gallic acid equivalent. The results indicate that iris has in vitro antioxidant properties, which can be the major factor responsible for the inhibition of lipid peroxidation. INTRODUCTION Reactive oxygen species (ROS) such as superoxide radi- cal (O 2 ·– ), hydroxyl radical (OH · ), and peroxy radicals (ROO · ) are produced as a part of normal metabolic proces- ses. The oxidative damages caused by ROS on lipids, prote- ins, and nucleic acids may trigger various chronic diseases, such as coronary heart disease, atherosclerosis, cancer, and aging [1]. Lipid peroxidation (LPO) and free radicals are known to be among the main causes for compromising the quality of food during processing and storage. Therefore, it is obvious that the prevention of LPO in the food is effective not only in the stability of nutritional content but also in the extension at the best-before date. In living systems, biomembranes are composed of lipids, including unsaturated fatty acids that re- act easily to form lipid peroxides and free radicals. The accu- mulation of lipid peroxides in living systems induces functi- onal anomalies and pathological changes [2 – 4]. According- ly, much attention has been paid to antioxidants, which are expected to act effectively to prevent food and living systems from peroxidative damage. Though butylated hydroxyaniso- le (BHA) and butylated hydroxytoluene (BHT), which are strong artificial antioxidants, have been much used in the food industry, they are suspected to be toxic in the lung and carcinogenic [5, 6]. Hence, the importance of research aimed at finding natural antioxidants has greatly increased in recent years [7 – 9]. Genus Iris (family Iridaceae) is represented by 37 speci- es in Turkey, of which 13 are endemic [10]. Most of the iris species are cultivated for ornamental purposes worldwide. In view of potential health benefits, there has been intensive re- search on natural antioxidants derived from plants. Recently, iris (Iris germanica L., family Iridaceae) has gained great at- tention from the cosmetic and perfume industries due to the their violet-like smell caused by irone-type compounds. Be- sides, Iris germanica was reported to have various biological properties, including potent antiulcer, anticancer, and piscici- dal activities [11 – 13]. Aqueous extracts of Iris germanica decrease smooth muscle activity in vivo, produce a musculot- ropic spasmolytic effect on the duodenum in vivo and in vit- ro, stimulate respiration, show a central antiserotonin activi- ty, and induce a transitory hypotension accompanied by a ne- Pharmaceutical Chemistry Journal Vol. 41, No. 8, 2007 409 0091-150X/07/4108-0409 © 2007 Springer Science+Business Media, Inc. 1 College of Arts and Sciences, Atatürk University, 25240 Erzurum, Turkey. 2 Department of Food Technology, Oltu Profession High School, 25400 Oltu/Erzurum, Turkey. 3 College of Education, Atatürk University, 25240 Erzurum, Turkey. * E-mail: demirn@yahoo.com