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Understanding Medicinal Plants: Their Chemistry and Therapeutic Action

Understanding Medicinal Plants: Their Chemistry and Therapeutic Action by Bryan Hanson. New York, NY: The Haworth Herbal Press; 2005. 307 pp. ISBN: 978-0-7890-1552-5. $44.95.

Are you passionate about learning the basic chemistry and pharmacology of medicinal plants? Were you frustrated by your college professor and then turned off for the rest of your life when dealing with chemistry and biomedical topics? If you say yes to one of these questions, then Understanding Medicinal Plants is the book for you.

This book is an excellent source of information for any college student who has a strong interest in the scientific knowledge required to understand the effects of herbs, as well as for those who are not so attracted to learning chemistry from traditional sources. It is also an exceptional foundation for lay people who want to expand their herbal chemistry and pharmacology knowledge beyond what they find in other magazines and publications.

Having taught physiology and pharmacology in several universities, I have personally witnessed many first-year undergraduate students who took an introductory course in chemistry or biology and then changed their academic goals to non-science. Perhaps these students would have chosen organic chemistry or pharmacology in their career paths if they had found a compassionate mentor, but instead they opted to discard the hard sciences from their curriculum altogether.

For us botanical scientists at heart, who religiously read HerbalGram, we learned chemistry and biology early in life. If we did not like a basic chemistry or biology topic, we would still swallow it as a bad prescription. We thought many of these concepts were absolutely necessary to understand the more complex and fascinating topics such as NMR spectroscopy, secondary metabolism in plants, toxicology, pharmacokinetics, and drug metabolism. If we were bored by the way they were presented, we took a deep breath and thought: “I’m sure this will expand my knowledge and horizons.” We made ourselves believe that the concepts were empowering tools to explore more complex and intricate subjects as we advanced into higher level classes.

However, let’s face it. For the bulk of college students, accustomed to quick visual streams of information and not as interested in science textbooks as many of us, digesting these basic concepts can be a source of frustration. Perhaps we have been taught to believe the hard sciences are just for a privileged group of geeks or those brave enough to pile stacks of information in their brain.

Fortunately, we now have an excellent book and a great teacher who understands college classroom realities in the 21st century and the challenges of teaching biomedical sciences. Dr. Hanson, a professor of chemistry at DePauw University in Greencastle, Indiana, introduces basic chemical and pharmacological concepts clearly and seamlessly, so that students can learn about chemical bonds, secondary metabolism in plants, neuropharmacology, and DNA replication, all from just one source. I have not been in Dr. Hanson’s classroom, but I am pretty sure his students don’t think these topics are boring.

The book includes, among other things, the symbolism of chemical structures, the origins of bonding and molecular properties, and a structural lexicon of medicinally important chemical families found in plants. It reviews the chemical behavior of medicinal molecules (often extracted and purified as drugs), as well their applications. The last two chapters are my favorites—and yes, I am showing a personal bias as a pharmacologist. Dr. Hanson explores the pharmacological action of plant molecules by touching on drug delivery and action, introducing the concept of receptors and molecular targets, as well as providing a clear explanation about levels of action. A very fascinating group of case studies of selected plant drugs is included, which I expect to be particularly appealing to students.

The last section addresses an all-time favorite—the traditional South American ritual concoction ayahuasca and its effects on the central nervous system. It touches on the complex chemistry and effects of B-carboline alkaloids, harmine, harmaline, and tetrahydroharmine, as well as the structural similarity of key ayahuasca molecules with lysergic acid (LSD) and serotonin. It also deals with the complexity of serotonin receptors and how various compounds in this complex plant mixture create the “therapeutic” effect, which is still far from being completely understood.

In an unassuming tone, the book also explains the complex chemistry of ginkgo (Ginkgo biloba, Ginkgoaceae) extract and its antioxidant and pharmacological effects on cerebral circulation, possibly contributing to the medicinal effects. It also describes a number of cancer treatments from plants and natural sources, including an explanation of cell cycle and DNA replication. Thus we learn about the effects of colchicine from autumn crocus (Colchicum autumnale, Liliaceae), paclitaxel from the Pacific yew tree (Taxus brevifolia, Taxaceae), vinca alkaloids from the Madagascar periwinkle (Catharanthus roseus, Apocynaceae), and camptothecin from the Chinese happy tree (Camptotheca acuminata, Nyssaceae).

Any undergraduate student can greatly benefit from this book. Not just the biology, chemistry, and pre-med or pre-pharmacy majors, but also the students studying general education, anthropology, or psychology.Professional students already enrolled in pharmacy and medicine programs will also find invaluable details on the chemistry and pharmacology of medicinal plants, which can serve as an important source of reference in their careers.

I encourage any university program interested in attracting culturally diverse students to acquire the book. It is a useful reference for learning basic topics in chemistry and physiology, and it would be an asset to any college library that wants to offer more cultural and historical context about the science of medicinal plants.

An example of how the author engages people to learn is demonstrated by the way he describes how ginkgo fossils have been found that are 200 million years old and how this plant was rescued from becoming extinct by Buddhist monasteries in China.This is followed by a brief discussion of its historical use in China and its more current use as a concentrated and chemically standardized extract in Europe and the United States, where it has been adapted to treat aging conditions and the early stages of Alzheimer’s disease. The historical and cultural references are an excellent way to motivate students to learn more about the chemistry and the pharmacology, which are presented later using a very readable format.

Congratulations to the author in accomplishing a powerful goal—bringing a simple message to students and lay people. Chemistry and pharmacology of medicinal plants really can be interesting and fun to learn!

—Ezra Bejar, PhD Director of Technical SciencesHerbalife International, Inc.