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Handbook of Chinese Medicinal Plants: Chemistry, Pharmacology, Toxicology

Handbook of Chinese Medicinal Plants: Chemistry, Pharmacology, Toxicology by Weici Tang and Gerhard Eisenbrand. Weinheim, Germany: Wiley-VCH Verlag GmbH & Co.; 2011. Hardcover; 2-volume set; 1282 pages. ISBN: 978-3-5273-2226-8. $405.00.

The Handbook of Chinese Medicinal Plants by Tang and Eisenbrand is a much expanded, updated, and reformatted edition of their 1992 book, Chinese Drugs of Plant Origin, in which these expert authors gathered and interpreted published reports on Chinese medicinal plants. Given the plethora of research papers on Chinese herbs produced since 1992 and the expanded interest in Chinese medicinal herbs as sources for unique drugs, this new effort by Tang and Eisenbrand is most welcome.

The 2 volumes are a collection of monographs, arranged alphabetically by botanical names. Aside from the near doubling in number of monographs from their prior publication—from 124 to 231—there has been a shift in emphasis from chemical constituents to pharmacology. This shift reflects the fact that chemical analysis for the major active components of these herbs was largely completed by the time of the earlier book, while extensive pharmacological research with good cellular and animal models was just getting started.

For those who are familiar with summaries of scientific research on Chinese medicinal herbs, I would compare this to Handbook to Chinese Materia Medica by Zhu Youping, published in 1998, which was primarily an updated and simplified version of the 1976 2-volume Pharmacology and Applications of Chinese Medicinal Materials by Chang and But. Zhu’s collection of monographs is arranged by Traditional Chinese Medicine categories and reports on nearly 300 herbs, which covers many of the standard items used by practitioners. The new Handbook is far more comprehensive in describing Chinese herb research than these previous publications and supersedes their source materials.

A key feature of the Handbook of Chinese Medicinal Plants is that it is well written. As long as the reader is armed with the technical terminology of chemical and pharmacological analysis, it is relatively easy to get a good sense of what each herb is about. The shortest monographs are informative 2-page compilations, such as for Dipsacus asper (Dipsacaceae), Juncus effusus (Juncaceae), Momordica grosvenorii (Cucurbitaceae), and Polyporus umbellatus (Polyporaceae) [Chinese: xuduan, tengxincao, luohanguo, and zhuling respectively], while there are several with 6 to 10 pages or more that cover an array of pharmacological properties, such as for Angelica sinensis (Apiaceae), Eucommia ulmoides (Eucommiaceae), Panax ginseng (Araliaceae), and Sophora flavescens (Fabaceae) [Chinese: danggui, duzhong, renshen, and kushen, respectively]. The authors conducted an intensive search of the literature; the majority of references were published after those that were used for Chinese Drugs of Plant Origin. For practical reasons in compiling such a large work, most of the references in each monograph were published before 2005 to 2007. Through their diligent efforts, the authors successfully provide the essential background into which one can then place new reports on these herbs.

The primary target audiences for the Handbook would include the following: researchers in university departments of pharmacy, pharmacognosy, and medicinal chemistry; investigational drug researchers; product development specialists working for the nutraceutical, dietary supplement, or herb industry; and herbalists who want to have a good summary of scientific research that is available for commonly used Chinese herbs. It would be an essential book for university libraries and for libraries of the colleges where Chinese medicine is taught.

The technical jargon is usually dense, and I will give a brief example from the pharmacology section of the monograph on Prunella vulgaris (Lamiaceae), the Chinese herb xiakucao:

2α,3α-Dihydroxursolic acid demonstrated a significant inhibition of the release of β-hexosaminidase by cultured RBL-2H3 cells in dose-dependent manner, with an IC50 value of 57 µM. Ursolic acid and 2α-hydroxyursolic acid strongly each inhibited the production of nitric oxide from cultured murine macrophages, RAW 264.7 cells, with IC50 values of 17 and 27 µM, respectively.

The plant components mentioned here are triterpenes that were listed in the chemistry section of the Prunella monograph. Triterpenes are important components of several key Chinese herbs, and ursolic acid is a widely occurring and pharmacologically-interesting compound in herbal medicine that occurs in plants along with the methylated variant, oleanolic acid. The hexosaminidases are enzymes that affect brain function; nitric oxide (NO) is one of the most intensively studied compounds in human physiology. The molecule has an impact on numerous physiological functions, including relaxation of smooth muscles and a neurotransmitter for certain brain cells and motor neurons. The effects of NO are usually measured in cell cultures, in this case from rat and mouse immune system blood cells, with the ursolic acid and hydroxyursolic acid showing a rather strong activity. These findings may not reflect upon the usual use of Prunella in clinical practice, but point to the potential medicinal and nutraceutical uses of ursolic acid and its derivatives, which are now obtained by technical extraction procedures that yield high levels of these compounds.

To illustrate the important contributions of this Handbook compared to previous literature, consider an herb that has recently been in the news for its potential as an anti-inflammatory drug: Andrographis paniculata (Acanthaceae; Chinese: chuanxinlian). The herb was described earlier in Chinese Drugs of Plant Origin, the entry for which had 27 references from 1911 to 1987; 4 pages of the initial monograph were devoted to chemistry, with many chemical structure diagrams, and just over one page to pharmacology. In the new handbook, there are 79 references from 1971-2006, with 2 pages devoted to chemistry, reducing the space allotted for structure diagrams and eliminating discussion of the historical aspects of the chemical analysis and extraction; but 5 pages to pharmacology (and toxicology), incorporating several new findings. The main active component of this herb is andrographolide, a diterpene lactone, and though some of the newer applications of interest are not in this monograph, there are reports here showing hepatoprotective effects, antihyperglycemic action, immunostimulant activities, and cardiovascular modulating properties, among others.

For those looking at direct clinical applications of Chinese herbs, this Handbook is not a source; it has a very limited review of the traditional uses in the introductory section of each monograph and only rarely mentions research reports on clinical work. This is by design rather than any failing, as the text is devoted to chemistry, pharmacology, and toxicology. Most clinical studies of Chinese herbs—such as summarized in Zhu’s Chinese Materia Medica—are fraught with difficulties in research design and reporting, requiring accessing the original reports rather than relying on short overviews, as can be presented successfully for chemistry and pharmacology data, excellently done by Tang and Eisenbrandt in their Handbook.

—Subhuti Dharmananda, PhD Founder and Director Institute for Traditional Medicine and Preventive Health Care Portland, OR