The following review is provided by the American Botanical Council (www.herbalgram.org), as part of the HerbClip [TM] Education Mailing Service. For more information, see the credit at the end of this article.

Medicinal plants have been used for therapeutic purposes since the beginning of civilization. Following a recent period in Western medicine when plant medicines were shunned, there has been a resurgence of interest in plant compounds with beneficial pharmacological properties. The development of these agents is a long and expensive undertaking. This paper outlines the necessary steps to accomplish this task.

According to the author, development of new drugs can cost as much as $360 million and take a minimum of 10 years. Tens of thousands of compounds are tested before one possible drug is found, and large volumes of plant materials are necessary to obtain very small amounts of active compounds. The effort is multidisciplinary, requiring botanists, chemists, pharmacologists, toxicologists, and agronomists. Medically active plants can be used as teas or extracts, or they can be purified to active compounds. If the medicine is derived solely from a plant and retains the plant's chemical complexity, it is considered a phytopharmaceutical preparation or herbal medicine, If it is an isolated compound and prepared according to specific legal and technical procedures, it is considered a drug.

Plants chosen for drug development are most commonly selected based on their use in folk and traditional medicine. The study of these uses is called ethnobotany. Plants can also be selected based on chemical constituents known to their families or genera. This has been especially productive in toxic plants. Randomized searching for plants with specific pharmacological activities is another approach. Existing scientific literature can also be used to identify known compounds with promise. Use of natural resources for drug development must be accompanied by sustainable practices and respect for the environment and cultures where they originate. The most cornmonly sought-after treatments are antibiotics, anti-tumor drugs, contraceptives, anti-inflammatories, kidney protectors and drugs for psychiatric and tropical diseases.

Once chosen, a plant must be correctly identified and preserved. It is then analyzed for active compounds which are isolated using appropriately selected laboratory methods. Additional work is done to identify the chemical structure which will allow total or partial synthesis and alteration of the structure to improve efficacy (or reduce toxicity). Extensive efficacy and toxicity studies follow. Crude preparations of the whole plant can be developed as herbal remedies. Efficacy and safety studies are required in this case as well, but are less extensive, and, according to the author, historical use can be taken as proof of efficacy. (However, in the regulatory systems of some Western nations, historical use is not considered an adequate criterion for safety and efficacy.) Whole plant preparations are appropriate when a combination of compounds are active. Some of the challenges of developing crude preparations are low concentrations of active compounds, poor bioavailability, and solubility.

Because plant medicines are freely marketed in many parts of the world, toxic accidents sometimes result. These accidents can be due to mistaken identification of plants, inherent toxicity, and misuse. Some plants interfere with pharmaceutical drugs, including those containing coumarins, tyramine, estrogenic or photosensitive compounds, or those which cause allergic reactions.

A large percentage of the plants on Earth are found in Brazil; however, the pharmaceutical industry there is only in developmental stages. Herbal medicine companies are usually small, and research is limited to a small number of university staff. Quality standards remain minimal. The country is putting into place guidelines based on the World Health Organization, the European Scientific Cooperative on Phytotherapy, and the German Commission E, and is forging partnerships between the academic and pharmaceutical sectors. There is still much room for growth in the areas of research, publication of findings, and active collaborations. Finally, legislation is being developed to preserve the natural diversity of the country and encourage sustainable development of its resources.

Reference:

Rates, SMK 2001. Plants as source of drugs. Toxicon, 39: 603-613

The American Botanical Council (ABC) is the world's leading non-profit education organization disseminating science-based information promoting the safe and effective use of herbal medicine. This review was originally distributed as port of the HerbClip[TM] Educational Mailing Service. HerbClip and HerbalGram ore among the benefits of membership in ABC. To join ABC, logon to http://www.herbalgram.org/ or www.herbalgram.org. call 800-373-7105, or email abc@herbalgram.org.

RELATED ARTICLE: Antioxidant Herbs and Inflammatory Bowel Disease

Inflammatory bowel disease causes poor quality of life, and conventional therapies are not totally successful in preventing relapse or achieving remission. As a result, many patients try complementary medicine, especially herbs. While many herbals are said to be effective in chronic inflammatory conditions, there is little clinical and pharmacological data to support these claims. Reactive oxygen metabolites (ROM) are present in excess in inflamed colonic mucosa (lining of the colon) and are likely to play a role in inflammatory bowel disease. Therapies that have antioxidant activity may potentially be clinically useful. This paper (1) investigates the antioxidant effects in vitro of six herbs claimed to benefit inflammatory bowel disease and diseases such as rheumatoid arthritis.

The following herbs were evaluated: slippery elm (Ulmus rubra Muhl; Potter's Herbal Supplies Ltd. Wigan, U.K.), fenugreek (Trigonella foemum-graecum; Good'N Natural Manufacturing Corp. U.S. for Holland and Barrett, Nuneaton, U.K.), devil's claw (Harpagophytum procumbens; Bio-Health Ltd, Rochester, Kent, U.K.), Mexican yam (Dioscorea mexicana; Higher Nature, Burwash Common, East Sussex, U.K.), tormentil (The authors use the common name "tormentil;" however the Standard Common Name is cinquefoil. Potentillo erecto [L] Raeusch; Bioforce UK Ltd, Irvine, Scotland, U.K.), wei tong ning (Chian Academy of Traditional Chinese Medicine, Beijing, China). Entire plant extracts were tested. Orange juice was tested as a nontherapeutic control. Aminosalicylate, a purified pharmacological agent, was tested as a positive control. Super-oxide scavenging and peroxyl radical scavenging were examined in two different cell-free radical generating systems. Herbal effect on generation of oxygen radicals was examined in mucosal biops ies from patients with active ulcerative colitis.

In the superoxide assay, all herbs, except fenugreek. demonstrated dose-dependent antioxidant effects. In the peroxyl radical assay, all herbs had dose-dependent peroxyl-radical scavenging effects. In the inflamed biopsies, all herbs, except Mexican yam. had a significant antioxidant effect compared to control (P < 0.03 -0.05). Orange juice had no effect in any assay.

The cell-free techniques have many technical advantages but do not closely model the in vivo situation, The tissue assay is sensitive but it nonspecifically detects production of multiple different ROMs. The different methods complement each other but do not mimic each other. All of the herbs tested are likely to contain numerous biologically active and antioxidant compounds, including flavonoids.

Slippery elm, devil's claw, tormentil, and wei tong ning were antioxidants in all three assay systems, similar to aminosalicylates. These herbs should be evaluated in vivo for their therapeutic potential in treating patients with inflammatory bowel disease.

- Heather S. Oliff, Ph.D.

Reference:

(1.) Langmead Let al. 2002. Antioxidant effects of herbal therapies used by patients with inflammatory bowel disease: an in vitro study. Alimentary Pharmacology & Theropeutics, 16:197-205

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