in China, Huangdi Neijing (19), pungent flavor disperses, sweet flavor nourishes and these flavors pertain to yang. Sour flavor astringes, bitter flavor purges and salty flavor moistens and sour, bitter and salty flavors pertain to yin. For the different natures, Huangdi Neijing gave the following information: cold and cool natures belong to yin and hot and warm natures belong to yang. However, the yin and yang of things are relative, not absolute. Many herbs have two or more flavors and they are opposite, in this case there exists yin within yang and yang within yin. Drugs of different flavors, natures and different compositions show different pharmacologic and therapeutic actions. In Table 3, we compared the ORAC value of herbs with different natures, flavors and functions as well as the ascribed yin/yang properties of the sub-groups. The bitter and/or sour flavors belong to yin character and sweet and/or pungent belong to yang. For the different flavors, there was a significant difference in antioxidant value. Herbs with bitter flavor have a higher ORAC value than those with pungent and/or sweet flavors. The average ORAC value of herbs with bitter and/or sour flavor is 856 mmol TE/g, four times higher than herbs with sweet and/or pungent flavor (213 mmol TE/g). The highest ORAC value in the bitter and/or sour group is 1940 mmol TE/g, three times that of the highest in the sweet and/or pungent group (640 mmol TE/g). From Figure 1, of the first ten herbs that had ORAC value similar to or higher than vitamin E (1162 mmol TE/g) (20), 60% of them have bitter and/or sour flavor (yin). Nine of the 10 have a bitter flavor component. Bitter flavor has the actions of drying and eliminating dampness, lowering rebellious qi and purging heat. Those bitter in flavors are used widely. Damp-heat syndrome is the main syndrome where bitter herbs could be used clinically. An animal model for the study of damp-heat syndrome was developed by multiple factors (diet, climate and pathogenic biological factors) (21,22). The research showed that the activity of super-oxide dismutase (SOD) was lowered and malonyldialdehyde (MDA) increased markedly in red cells of damp-heat syndrome animals. Clinical research found an imbalance between oxidation and antioxidation of bronchitis patients with damp-heat syndrome. The antioxidant activity in the blood serum of the damp-heat syndrome group was lower than the healthy group and the non-damp-heat syndrome group (23). Of the herbs we tested, it is known that Lycopus lucidus is used to promote blood circulation, promote diuresis and relieve edema (edema was related to dampness in TCM theory). Salvia miltiorrhiza is used to promote blood circulation to remove blood stasis, cool the blood to relieve carbuncles, clear away heat from the heart and tranquilize the mind. Sanguisorba officinalis, Sophora japonica, Nelumbo nucifera are used to cool the blood and stop bleeding. They all had the same bitter flavor and showed high ORAC values. The mechanism of eCAM 2008;5(4) 433 action of bitter flavor herbs in clearing heat and removing damp might have a relationship with enhanced antioxidant activity. Phenolic or flavonoid compounds have long been recognized as potent antioxidants (24). Studies have shown that the active components of the yin herbs are mainly flavonoids, which are phenolic compounds with strong antioxidant activity (13). The three herbs with the highest antioxidant activity in our study, Spatholobus suberectus, Sanguisorba officinalis and Agrimonia pilosa were reported to contain flavonoids (25–27). Further research on compounds with antioxidant activity in the bitter flavor herbs should provide a better understanding of the ancient flavors especially abstract flavors, at a molecular level. We first consider in depth with taste and smell separately and then combine them with modern research. In smell receptors, a molecule’s specific size and shape activate the receptor, while in taste receptors specific chemical reactivity may be more involved. How it works for the combination of gustation and olfaction constituting ancient flavors in modern antioxidant research might be a new point of view (11). However, using a similar analysis we would expect the nature of cooling and function 4 (dispelling pathogenic heat from the blood systems) to also share high antioxidant properties and this was not the result obtained. Natures are also related to the yin/yang designation. In this study, the cooling/warming herbs and hence, the yin/yang designations based on these characteristics, were not different in antioxidant properties. Overall, our study is supportive of that of Ou et al. and provides some insights into the four natures and five flavors, that is, bitter flavor (belonging to yin) had high antioxidant value. It is obvious that only one pharma- cologic parameter in vitro from 45 herbs could not establish the antioxidant activity and relationship with their TCM characteristics conclusively and the demarca- tion between yin and yang is not as stark in our studies as in the Ou et al. publication. We attribute this to our criterion for including a medicine, being its application to circulatory conditions, while the earlier study selected plants and animals with the polar opposites of yin and yang. This support for traditional insights into medicines being consistent with mechanism of action studies is a recurring theme for natural products research and suggests biomedical research that supports the contribu- tion and the use of these medicines. References 1. Ou B, Huang D, Hampsch-Woodill M, Flanagan JA. When east meets west: the relationship between yin-yang and antioxidation- oxidation. FASEB J. 2003;17:127–29. 2. Wu CG, Zhu ZB. Basic Theory of Traditional Chinese Medicine. Shanghai: Publishing House of Shanghai University of Traditional Chinese Medicine, 2002, 23–4.