Effect of Rhizoma coptidis (Huang Lian) on Treating Diabetes Mellitus

The rapidly increasing diabetes mellitus (DM) is becoming a major public health issue globally; considerable progress has been made in the field of western hypoglycemic drug and insulin, but some shortages still exist. As one of the most important parts in complementary and alternative therapies, traditional Chinese medicine (TCM) performs a good clinical practice and is showing a bright future in the treatment of DM. TCM therapy has certain advantages of less toxicity and/or side effects, and Chinese herbal medicine which usually contains various active ingredients could provide multiple therapeutic effects. Huang Lian (Rhizoma coptidis, RC) is a herb frequently used in many traditional formulas for properties of "clearing damp-heat, quenching fire, and counteracting poison" in Asia for centuries. In this review, we summarize the application of RC in the treatment of DM from two aspects of contents. Firstly, theoretical principles are explained, including the properties and related records about RC in ancient references and modern pharmacological researches and pharmacokinetics on RC and its active components. Secondly, the clinical application of RC is mainly reviewed, such as applicable stage and syndrome, the reasonable dose range, the preparation formulations, and the toxicity and/or side effects and solutions to its adverse actions. This review provides scientific evidence about the effective components, pharmacological researches, and toxicity of RC, as well as introducing traditional Chinese medical theory and clinical experience, in order to guide clinician to use RC more suitably and reasonably in the clinical practice.