Application of microscopic techniques for the authentication of herbal medicines

Microscopic identification is the method most commonly used to authenticate Chinese herbal medicines. By means of various microscopic techniques, structural and cellular features of herbs are examined in order to determine their botanical origins and assess their qualities. This method is useful for identifying species from fragments or powders and for distinguishing species with similar morphological characters; it may also be useful for evaluating the pharmaceutical quality of herbs. In this chapter, techniques of preparing specimens for microscopic examination are described. Normal light microscopy combined with polariscope and fluorescence microscopy are introduced as they are used in the authentication of Chinese herbal medicines. Structures and cells of herbs have been found to possess stable and specific polariscopic and fluorescent characteristics that can be used to determine the botanical identify of herbal medicines. In addition, the future prospect of combining microscopes with chemical analysis to analyze the chemical profiles of herbal tissues is discussed. Establishing a correlation between microscopic features and active components distributed in a plant’s tissues will enable quality evaluation of Chinese herbal medicines by microscopy.