177 Radical Scavenger and Antioxidant Activities of Selected Medicinal Plants `. KØry, A. BalÆzs, L. Kursinszki, P. ApÆti* and . Szőke Department of Pharmacognosy, Semmelweis University, H-1085 Budapest, llői œt 26., Hungary *Chemical Research Center, Institute of Chemistry, Hungarian Academy of Sciences, Budapest, Hungary A. BlÆzovics and K. HagymÆsi II. Department of Internal Medicine, Semmelweis University, H-1085 Budapest, SzentkirÆlyi u. 46., Hungary . Nagy Solidago Kft. Budapest,. Hungary Keywords: radical scavenger activity, antioxidant activity, Sempervivum tectorum, antioxidant medicinal plants Abstract Oxidative damage that results in lipid peroxidation can inactivate cellular components and can have serious effects on the cells, probably leading to ageing as well as several diseases. In recent years much attention has been focused on this subject, especially in the field of clinical medicine. Several natural compounds from plants exhibit antioxidant and/or radical scavenger properties. It also has become clear that the direct free radical scavenging effect and/or membrane protection play an important role in the action mechanism of several old established drugs. The natural antioxidant nutrients also deserve attention as they offer the possibility to replace the optimal overall antioxidant status. The aim of the present work was to prove the phytotherapeutical significance of some officinal and popular medicinal plants on the base of their antioxidant activity due to their influence on pathological free radical reactions. Experimental methods were planned and developed in order to measure the antioxidant, free radical scavenging, immunmodulant, membrane protecting activities and to monitor the cholesterol-, lipid peroxidation-lowering capacity of plant extracts and enriched/isolated fractions. Complex phytochemical screening and analytical standardization was carried out considering the potential bioactive constituents, which were determined by chromatographic and spectroscopic techniques. The non-specific scavenger activities of the medicinal plant extracts were studied by the chemiluminometric technique. Relationships were proved between the quantity / composition of active ingredients and scavenger activities of the individual extracts. Our results so far suggest that medicinal plants, their phytotherapeutical preparation or isolated constituents as supplements of human diets are promising as preventative agents when free radical reactions are involved in the pathogenesis of diseases. As natural antioxidants seldom work singly by themselves but as part of a synergistic action of antioxidative systems, further studies are needed. INTRODUCTION Free radicals are formed constantly by the bodys normal use of oxygen, such as for respiration and some cell mediated immune functions. They are also found in or generated from environmental pollutants, cigarette smoke, car exhaust fumes, radiation or ultraviolet light, air pollutants, pesticides, and certain industrial solvents. Some medications and anesthetics form free radicals in vitro; they are also produced to excess in inflammatory responses and hemorrhaging. Free radicals can damage cell membranes and other vital cell components, such as genetic material in the cell nucleus, and can inactivate enzymes. Damage to body cells and molecules by oxygen containing free radicals has been implicated in a wide variety of diseases. The unsaturated fatty acids of lipids and lipoproteins are especially susceptible to Proc. Int. Conf. on MAP Eds. J. BernÆth et al. Acta Hort. 597, ISHS 2003