Radical Scavenger and Antioxidant Activities of Selected Medicinal Plants

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. Bernáth et al. Acta Hort. 597, ISHS 2003 178 free-radical mediated oxidation, and oxidative modification of LDL particles in the blood is believed to be an important part of the atherosclerotic process. Recently, lipid peroxidation has been suggested as a factor in degeneration of myelin in certain neurological diseases. Free radical damage to DNA is believed to play a role in initiation of carcinogenesis. Oxyradicals can also attack proteins, thereby changing their structure and ability to function. A variety of mechanisms provides defenses against free radical damage. Important antioxidants can be synthesized readily within the body. Metal binding proteins catalyse reactions, which eliminate reactive oxyradicals. Some of these antioxidant enzymes incorporate essential trace metals, like selenium, which are often classified as antioxidant nutrients. Certain dietary micronutrients play important roles in antioxidant defence. Vitamin C is effective in the body's aqueous compartments (plasma, cell cytosol). Vitamin E (tocopherol) and ubiquinol (coenzyme Q) provide antioxidant protection in the body's lipid phase. Carotenoids also are believed to provide antioxidant protection to lipid rich tissues. There are several so called coupled reactions or antioxidant interactions between them, which is also an important pathway for antioxidant protection in humans (Sami, 1995). Although complex, the protection provided by the natural antioxidant scavenger system of the organism seems to be inappropriate in certain diseases or in their prevention. Therefore the so called natural and synthetic antioxidants have been more widely employed for additional and adjuvant treatments. Research on the antioxidative effects of medicinal plants has rapidly become an active field of modern pharmacology. Presently, antioxidants are widely used in food processing. Their effects on organisms are so important that an extensive literature has appeared related to many aspects. These include experimental studies of antioxidant phenoloids distributed in traditionally used medicinal plants and plants with potential and beneficial effects on disorders related to free radical attacks. Taking into account the possible prooxidant character of the various phenoloids, and the pros and cons of antioxidant drugs, it is important to emphasize their potential importance and their place in medicine. We have to move away from considering them as drugs for treatment of diseases, and begin to concentrate on the idea that they may be drugs for the prevention of diseases (Cao et al.,1997). Our research group became interested about 10 years ago in proving the phytotherapeutical significance of some official or traditionally used medicinal plants on the base of their antioxidant activity due to their influence on pathological free radical reactions. Because of the Janus-face properties of some poly-OH substituted phenoloids, many-sided in vitro and in vivo experiments had to be performed (Blázovics et al., 1993; Hänsel, 1994; Kéry et al., 1992). MATERIALS AND METHODS Plant Materials Vegetable drugs involved in screening works were purchased at drugstores; specimens are deposited in the Department of Pharmacognosy, Semmelweis University. Sempervivum tectorum L. (Crassulaceae), for detailed studies, was collected from the Botanical Garden of the University of Horticulture, Soroksár. An herbarium specimen is deposited in the Department of Pharmacognosy, Semmelweis University, where it was identified. Medicinal plant parts used: Anthriscus cerefolii herba, Anthriscus cerefolii radix, Calendulae flos, Cichoriae herba, Cichoriae radix, Epilobii herba, Equiseti herba, Filipendulae herba, Helychrisi flos, Hyperici herba, Millefolii herba, Petroselini radix, Petroselini folium, Raphani sativae radix, Sambuci flos, Sempervivi tectori folium, Solidaginis herba, Taraxaci folium, Taraxaci radix, Tiliae flos, Urticae folium and Veronicae herba. The plant samples were extracted with water, methanol and in some