430 Antioxidant and TCM characteristics the hyperactivity or hypoactivity of yin or yang and help the body restore its normal physiologic functions. All herbs possess four natures and five flavors. The four natures—cold, hot, warm and cool are summarized mainly from the body’s response after Chinese herbs are taken, which are so defined in relation to the properties, cold or heat of the diseases treated. In addi- tion, there are also some herbs known as neutral ones, whose cold or hot nature is not so remarkable and whose action is relatively mild, but these herbs still have differ- ences in their tendencies to cool or warm so that they are still in the range of four natures. The five flavors are the pungent, sweet, sour, bitter and salty that can be tasted with the tongue. With the development of the theory dealing with the medicinal properties, the flavors could best be described as abstract concepts, as the flavor defi- nitions have arisen more from observations of the clinical actions of the herbs than from the taste sensations. Most herbs contain a combination of a number of flavors, for example ‘bitter with sweet and pungent’ (4). The nature and the flavor are two kinds of medicinal properties that every Chinese herb possesses. Modern scientific research has been undertaken on the four natures since 1960, mainly in China and Japan. There are two main research areas on the four natures. The first is pharmacodynamic research, exploring the effect of cold and hot herbs on central nerve transmitters, sympathetic- adrenomedullary system, prostaglandin and endocrine system. The second is substantial foundation research, including chemical components and especially trace elements (5). Some innovative research was from biophysics and biochemistry to study the natures of Radix ginseng, Folium ginseng, Flos ginseng and Radix quinquefolium using a microcalorimetry method (6–8). The effects of four natures of 60 Chinese herbs were observed on organs and tissues of IRC/F1 mice using 14C-2-deoxy-glucose and autoradiography. The results showed that there were character distinctions among four natures on organs and tissues (9). Compared with the research on natures, the study on flavors has focused on the relationship between chemical component and differ- ent flavor (especially abstract flavor) and the pharmaco- logic actions of the main components (4,10) in China. It is interesting to note that a recent submission to Nature relate the pharmacologic activities of Ibuprofen and Oleocanthal to their similarities of taste. This is one of the rare scientific reports noting common pharmacologic activity for compounds with similar taste (11). Herbs of different natures and flavors exhibit different effects and are categorized differently in terms of yin and yang (12). Chinese herbs are also mainly classified on the basis of their function in theory and in the clinical setting. For the circulation- related herbs described in this study, they are classified as (12,13): function 1— drugs whose principal effects are to stop internal and external bleeding, function 2— drugs that make free the passage of blood in the vessels, promote blood circulation and disperse blood stasis, function 3— drugs that nourish the blood and are indicated for syndromes of blood deficiency and, function 4— drugs with the effects of dispelling pathogenic heat from the blood systems. These theories are the essential basis for the analyses and clinical usage of Chinese herbs. A recent study by Ou et al.(1) into the antioxidant capacities of 24 commercially available plant-based medicines inspired this study. They reported a striking relationship between in vitro antioxidant capacity and yin-yang classification of the herbs. Yang herbs had the lowest antioxidant values, yin herbs had the highest. The utility of antioxidant therapies in many diseases is well recognized. Cellular damage arising from an imbal- ance between free radical generating and scavenging systems has been implicated in the pathogenesis of a wide range of disorders, including cardiovascular disease, cancer and aging (14). Many Chinese herbs have already been reported as having antioxidant effects (15,16). To further explore the antioxidant nature of Chinese herbs and to assess the relationship between antioxidant capacity and the characterization of herbs within TCM, we tested the antioxidant effect of 45 herbs extracted with water. Methods Chemicals and Apparatus Trolox (6-hydroxy-2, 5, 7, 8-tetramethyl-2-carboxylicacid, a water soluble homologue of vitamine E) and fluo- rescein {30, 60-dihydroxy-spiro [isobenzofuran-1 (3H), 90 (9H)-xanthen]-3-one disodium; FL} were obtained from Aldrich (Castle Hill, NSW, Australia). AAPH (20-Azobis(2-amidinopropane) dihydrochloride) was pur- chased from Wako Pure Chemical USA (Richmond, VA, USA). The 96-well polystyrene microplates were pur- chased from PerkinElmer Life and Analytical Sciences. All ORAC analyses were performed on a Victor 2 plate reader (Wallac). Samples The samples in this study were purchased from Shanxi Provincial People’s Hospital. The herbs were identified by Shanxi Provincial Medicinal Materials Supervision Bureau and the vouchered specimens were stored in sealed containers at room temperature (10–20 C). The herbs were dried under high vacuum to constant weight and ground into powder. Dried herbs (3 g) were placed in a centrifuge tube (20 ml) and mixed with water (10 ml). After 2 h at room temperature with vortex mixing and 15 min in a sonicating water bath, extracts were centrifuged (5000 g, 10 min) and the supernatants removed. Supernatants were dried under high vacuum