Processing methods and the underlying detoxification mechanisms for toxic medicinal materials used by ethnic minorities in China: A review

Various toxic medicinal materials have been used by different ethnic minorities in China for thousands of years because of their extraordinary pharmacological activities. However, the improper use and complex toxicity-efficacy relationship could cause poisoning and even death. Therefore, the study of toxicity-attenuating methods and mechanisms is necessary.This review aims to summarize commonly used toxic ethnomedicines and their processing methods as well as the underlying mechanisms to potentially reduce toxicity and even enhance or preserve efficacy. Prospective for possible future investigations is also discussed.Processing methods and mechanisms are investigated mainly through literature review.Processing methods with heating (boiling, stir frying, and steaming, etc.) and without heating (soaking) are usually used by Chinese ethnic minorities to attenuate the toxicity of ethnomedicines. Wheat bran, vinegar, wine, and herbal decoction are commonly used processing excipients. The mechanisms of detoxification by processing can be briefly summarized into three major categories: (1) direct elimination of impurities or reduction of toxic constituents' contents of ethnomedicines by cutting, washing, soaking or frosting; (2) chemical structure transformation of toxic constituents, such as alkaloids, glycosides, toxic proteins, animal toxicants, and mineral components, during heating and/or soaking; and (3) biological synergism or antagonism effects between the chemical constituents of processing excipients and ethnomedicines in vivo, to reduce toxicity and protect target organs.Toxic ethnomedicines have long been used in China, and detoxification by processing is the prerequisite for their safe clinical application. However, understanding on the special processing methods and detoxification mechanisms of ethnomedicines in China remains insufficient. Investigations on quality control of toxic ethnomedicines, as well as evaluation of processing methods and studies of the corresponding mechanisms should be further strengthened for safe and effective clinical application.