The genus Litsea in traditional Chinese medicine: An ethnomedical, phytochemical and pharmacological review

Abstract

Ethnopharmacological relevance

The genus Litsea, mainly distributed in the tropical and subtropical regions, has been used in traditional and indigenous Chinese medicines for the treatment of diarrhea, stomachache, dyspepsia, gastroenteritis, diabetes, edema, cold, arthritis, asthma, pain, traumatic injury, etc. for a long history. The present review aims to provide a comprehensive summary on the ethnomedical uses, phytochemistry, and pharmacology of the Litsea species used in traditional Chinese medicine (TCM). Based on these data, evidences supporting their ethnopharmacological effectiveness are illustrated, and opportunities for the future research and development as well as the therapeutic potential of this genus are analyzed to highlight the gaps in our knowledge that deserves further investigation.

Material and methods

Information on the Litsea species was collected via electronic search (using Pubmed, SciFinder, Google Scholar, Web of Science and CNKI) and a library search for articles published in peer-reviewed journals. Furthermore, information was also obtained from some local books on ethnopharmacology.

Results

Twenty plants of the genus Litsea are found to be important traditional medicines in China, and have a long medicinal application for diarrhea, stomachache, dyspepsia, gastroenteritis, diabetes, edema, cold, arthritis, asthma, pain, traumatic injury, etc. Over 200 ingredients have been identified from these 20 Litsea species used in TCM, and flavonoids, terpenoids and alkaloids are considered as the characteristic and bioactive constituents. The crude extracts and the isolated metabolites of these medicinal plants have exhibited some in vitro and in vivo pharmacological effects, including antimicrobial, hepatoprotection, anti-inflammatory, antiasthmatic, immunomodulation, anti-diabetic, anticholelithogenic, as well as function on central nervous system, etc.

Conclusions

The extensive literature survey reveals Litsea species to be a group of important medicinal plants used for the ethnomedical treatment of gastrointestinal diseases, diabetes, inflammatory disorders, and microbial infection in TCM. Pharmacological investigations have supported the use of some Litsea species in the traditional medicines. In addition, further researches targeting individual ingredients responsible for the pharmacological effects, as well as their mechanisms of action are necessary. The outcome of these studies will further support the therapeutic potential of the genus Litsea, and provide convincing evidences to its future clinical applications in modern medicine.

Introduction

The genus Litsea, belonging to the family Lauraceae, contains approximately 200 plant species, which are mainly distributed in the tropical and subtropical regions around the world (Richter, 1981). It is documented that 74 plant species of this genus have been found in China, most of which are growing in the regions between 18° and 34° north latitude of Southern and Southwest China, including Anhui, Zhejiang, Fujian, Yunnan, Sichuan and Tibet provinces (Flora of China Editorial Committee, 1994). In the aspect of ethnomedicine,20 plants in Litsea species have a long history of use in traditional and indigenous Chinese medicines (Xie and Yu, 1996). Fruit of the plant is the commonly prescribed medicinal part for the treatment of gastrointestinal diseases, pain, asthma, and traumatic injury. Meanwhile, the leaves, stems, velamina, roots and barks have also been adopted to treat people suffering from stomachache, cold, pain, arthritis, diarrhea, traumatic injury, etc. (Editorial Committee of Zhonghua Bencao National Traditional Chinese Herb Administration, 1999, Xie and Yu, 1996, Xie and Liang, 1996).

A great deal of studies concerning the phytochemical and pharmacological aspects of the genus Litsea have been carried out. More than 200 chemical ingredients, covering flavonoids, terpenoids, alkaloids, butanolides and butenolactones, lignans, amides, steroids, fatty acids, megastigmanes, etc., have hitherto been isolated from these 20 plants medicinally used in traditional Chinese medicine (TCM). Of these chemical ingredients, flavonoids and terpenoids are regarded as the two groups of bioactive substances that are responsible for the observed pharmacological effects of Litsea species (Chen et al., 2004, Tang et al., 2013, Wan et al., 2006, Wang and Liu, 2010, Wang et al., 2009, Ye et al., 2006). Extracts of plants from this genus, as well as the purified molecules, demonstrate a wide spectrum of pharmacological functions, involving in antifungal (Yang et al., 2010), antibacterial (Chen and Xu, 2013), antidiarrheal (Mandal et al., 2000), anti-inflammatory (Tang et al., 2013), anti-arthritic (Zhou et al., 2010), anti-HIV (H. Zhang et al., 2003), anti-asthma (Yin et al., 2006), hepatoprotective (Wang et al., 2009), immunomodulatory (Hu et al., 2007), and anti-diabetic properties (Sun et al., 2010), confirmed by experiments in vivo and in vitro.

Several reviews dealing with the phytochemistry and pharmacology of the genus Litsea have been reported. Two reviews focusing on terpenoids and alkaloids from Litsea species and their biological activities have been published (Xie and Zhang, 1999, Zhao, 2006). Recently, Agrawal et al. (2011) comprehensively summarized the chemical ingredients isolated from the genus Litsea before the year of 2009, and also briefly introduced their biological activities. Different from writing objectives of above literatures, the present review focuses on the research progress targeting the Litsea species used in TCM, to provide a comprehensive summary on the ethnomedical uses, phytochemistry and pharmacology of these plants. Besides, correlations of ethnomedical uses, phytochemistry and pharmacology have been discussed based on the research findings of these fields (Arora and Kaur, 2007, Mandal et al., 2000, Chen and Xu, 2013, Wang and Liu, 2010, Devib and Meera, 2010, Chen et al., 2004, Zhong et al., 2013, Zhang and Di, 2008, Zhou et al., 2007, Wang et al., 1999, Wang et al., 2009; Tu et al., 1985, Fang et al., 2002, Qian et al., 1980, Yin et al., 2006, Lv et al., 2008).