Chinese medicinal herbs as source of antioxidant compounds--where tradition meets the future

Medicinal plants are an essential part of Traditional Chinese Medicine (TCM), an ancient complex therapy considered today as one of the most complete complementary medicine system. Chinese Herbal Medicines (CHM) listings included in Chinese Materia Medica cover more than 1500 plants and a great number of composite preparations. Recently, several TCM herbs have been included into European Pharmacopoeia and many more are on the waiting list. The efficiency of TCM is based on the reinforcing of an organism's natural healing power and the ability to restore the energy homoeostasis. A likely mechanism of at least some of the activities is interacting with redox balance and prevention of oxidative stress. During the past two decades, hundreds of crude herbs, extracts, and isolated compounds have been screened for their antioxidant properties in vitro and in vivo. Consequently, some of traditional Chinese herbs can be regarded as source of very efficient antioxidant compounds, and this activity could explain some of their therapeutic and preventive usefulness. In this review, we outline the recent achievements in the worldwide quest for more efficient antioxidants, with Chinese medicinal and food plants in the central point. Various classes of antioxidant compounds will be mentioned, such as polyphenols or terpenoids that can act either as direct reactive oxygen species scavengers, transition metal reducers and chelators, or as chain breaking antioxidants. Some methodological considerations will be also discussed, with emphasis on the potential importance of the results obtained with antioxidant assays for human health and disease prevention. In this context, several examples of selected, most promising Chinese medicinal plants will be also presented in more detail.