Abstract
Since prehistoric times, humans have used natural products, such as plants, animals, microorganisms, and marine organisms in medicines to alleviate and treat illness. These remedies are often prescribed as part of traditional medicine, a discipline that has been built over the ages based on empirical knowledge that was passed down through the generations. Herbal remedies are aimed at wellness and general disease states, whereas conventional pharmaceuticals are directed at specific molecular disease targets.
Herbal remedies come from various sources where growth, harvesting, and storage conditions can alter the amount of the active ingredients substantially. In addition, fungal and other organic and inorganic contaminants add to the complexity of safety assessment. Sometimes adulterants are intentionally added for the purpose of efficacy.
Herbal remedies are labeled as mg of the plant, an extract (in mg or percent), or the active ingredient in mg, e.g., capsules containing 80 mg of the herb [Ginger root 750 mg], or capsules containing 80 mg of the active [Saint John’s Wort 300 mg–0.3% hypericin], or as a straight concentration [CBD oil 2.5%] for the purpose of dosage. The therapeutic index for herbal remedies is large: the recommended doses for herbs are usually in milligrams per 70 kg person compared to toxicity experiments that require grams per kilogram for an effect. This does not mean that herbal remedies are innocuous, as most users are aware of the intrinsic hazard of some herbal remedies and risk of exposure, cigarette smoking, for example.
In toxicologic pathology, the organ of impact following herbal remedy overdose, like conventional pharmaceuticals, is usually the liver. However, toxicity can be seen in other organs such as the heart, following Digitalis exposure. Goldenseal root power [Hydrastis canadensis]), Gingko biloba extract [Ginkgo biloba], Riddelliine (pyrrolizidine alkaloid), Pulegone [Mentha sp.], Kava kava [Piper methysticum], and Indole-3-carbinol [Brassica sp.] are hepatotoxic at the doses given experimentally. In addition, some herbs have been classified as carcinogens based on experimental evidence. The International Agency for Research on Cancer (IARC) has reviewed the evidence for carcinogenic activity for four of these herbal remedies (Goldenseal, Gingko, Kava, and Pulegone), and classified them as “possibly carcinogenic to humans” (Group 2B) because of evidence for carcinogenic activity in two species or both sexes of the same rodent species.
Other target organs damaged during high exposure include the gastrointestinal tract: Aloe vera and Senna; kidney: Aloe vera, raw Garlic, Ginkgo, Kava kava, Pulegone, St John’s wort, and Tobacco; heart: Ephedra; and the vascular system: Riddelliine pyrrolizidine alkaloid and Tobacco.
Milk thistle, Turmeric oleoresin, Green tea extract studies did not provide clear evidence for carcinogenic activity in rodent model systems nor did Marijuana, Chamomile, Coffee, Cocoa, Echinacea, Ephedra, Ginger, Ginseng, St. John’s wort, and Turmeric.
The scope of this chapter is limited to herbal remedies. Other supplements will not be part of the discussion except to illustrate specific points regarding herbal remedies. In this chapter we explore the use of herbal remedies in medical treatment regimens, differentiate traditional from scientific knowledge and discovery, the issue of quality in herbal remedies, and the difficulties in obtaining precise dose–response data for safety and efficacy.