June 2014 903 Biol. Pharm. Bull. 37(6) 903–915 (2014) © 2014 The Pharmaceutical Society of Japan Prospecting for Bioactive Constituents from Traditional Medicinal Plants through Ethnobotanical Approaches Ronghui Gu, a Yuehu Wang, b Bo Long, c Edward Kennelly, d Shibiao Wu, d Bo Liu, a Ping Li, a and Chunlin Long* ,a,b a College of Life and Environmental Sciences, Minzu University of China; Beijing 100081, P. R. China: b Kunming Institute of Botany, Chinese Academy of Sciences; Kunming 650201, P. R. China: c School of Life Sciences, Yunnan University; Kunming 650091, P. R. China: and d Lehman College, City University of New York; NY 10463, U.S.A. Received January 26, 2014 Pharmacologically active constituents from traditional medicinal plants have received great attention as sources of novel agents, pharmaceutical intermediates, and chemical entities for synthetic or semisynthetic drugs due to their potent pharmacological activities, low toxicity, and economic viability. Numerous compo- nents have been isolated from traditional medicinal plants, including alkaloids, flavonoids, and terpenoids, and clinical and experimental studies suggested that these components have useful pharmacological proper- ties such as antiinfectious, antioxidative, and antiinflammatory effects. In this review, modern ethnobotanical approaches to explore folk medicinal plants as candidates for drug discovery with the greatest possibility of success are discussed. Determining the bioactive mechanisms and tracing structure–activity relationships will promote the discovery of new drugs and pharmacological agents. Key words bioactive constituent; traditional medicinal plant; antioxidative; antiinflammatory; drug discov- ery; modern ethnobotany 1. INTRODUCTION As more people become aware of the potency and side effects of synthetic drugs, there is increasing interest in natu- ral product remedies with diverse chemical structures and bio- activities against different diseases. Typically, many of these natural products are plant secondary metabolites (PSMs), and the major pharmacologically useful groups of PSMs can be divided into several categories that include alkaloids, flavones, terpenes, phenolics, and polyphenols 1,2) that have antiinfec- tious, antioxidative, and antiinflammatory effects. Twelve thousand plant-derived agents have been isolated in the past decades. 1) Approximately 30 plant-derived anticancer com- pounds were reported to be clinically active against various tumor types and used in clinical trials, 3) such as taxol, podo- phllotoxin, vinblastine, and others. PSMs are not only consid- ered as direct sources of new pharmaceuticals but also provide unlimited opportunities for new drug leads because of their unmatched chemical diversity. 4) The extensive research on different plant species and their therapeutic principles have led to a reevaluation of traditional medicine systems, including ayurveda, unani, and traditional Chinese medicine. 5,6) Many traditional medicinal plants (TMPs), which form part of traditional medicine, have the ability to synthesize plant-derived bioactive substances. In addition, TMPs have been used with varying success rates to cure and prevent disease throughout history. For these reasons, screening pharmacologically active ingredients from TMPs would be optimal in terms of efficiency, safety, and economics. Written records of medicinal plant use date back at least 5000 years to the Sumerians, and archeological records suggest even earlier use of medicinal plants. 7) Pro- found knowledge of medicinal plants in traditional cultures developed through trial and error over centuries, and the most important experiences were passed on verbally from one gen- eration to the next. 6) Unfortunately, knowledge of TMPs has not reached a stable peak 8) but is eroding rapidly due to the disinterest of younger generations and the dying off of older generations who possess the knowledge. 9) Ethnobotany plays an increasingly important role in preserving disappearing traditional knowledge, especially traditional medicinal knowledge. Ethnobotanical surveys to document the traditional uses of various indigenous plants not only recognize this undocumented knowledge but also provide new avenues for pharmacological investigations to improve healthcare for a range of ailments. 9,10) In addition, ethnobotani- cal information offers a viable alternative to high-throughput screening of bioactive substances. 11) For drug discovery, phy- tochemical and pharmacological research based on modern ethnobotany is considered a validating approach in the search for novel chemical entities and frameworks with potential as drug leads. 6,11,12) It is estimated that 122 drugs from 94 plant species have been discovered through ethnobotanical leads, 13,14) such as morphine, the main anesthetic alkaloid in opium, or vincristine, an antitumor compound. 15) In addition to medicinal plants, folk practices are an im- portant part of traditional medicine which can lead to phar- macologically active ingredients and new pharmaceutical discoveries. This review discusses pharmacologically active constituents from TMPs, including categories, pharmacologi- * To whom correspondence should be addressed. e-mail: chunlinlong@hotmail.com The authors declare no conflict of interest. Current Topics Pharmacologically Active Constituents from Plants Used in Traditional Medicine