Introduction

As herbal medicines have been in use for thousands of years, herbal practitioners began written records on what specific foods and plants had healing properties that could be used to treat illness. They evaluated, defined, and recorded herbal pharmacological categories, the safety of herbs, what herbs could or could not be combined due to potential toxicity. The best growing locations for herbs was important, and instructions for the harvesting, processing, and proper storing techniques for herbs, was well-documented. In this way, the knowledge of herbal medicines was passed down from generation to generation. The therapeutic value of botanical medicines depends on the species of plant used, growing conditions, and biologically active constituents.

Herbal medicine toxicity factors include inappropriate dosing and duration of treatment, improper processing, using the wrong species of plant, use of known toxic herbs, adverse herb-drug interaction, individual patient sensitivity, adulteration and sale of herbal medications contaminated with pharmaceutical drugs, heavy metals, pesticides or other chemicals [1–3]. Herbal medicines are not considered drugs by many consumers and are considered to be safe because they are “natural” and so are often considered safer than conventional drugs, and may be administered at higher doses and for longer periods of time than is recommended. It is critical that all herbal medicine prescribed contains all the correct plant family and species before dispensing. The use of an incorrect species of plant can cause severe disease or death, (e.g., Aristolochic acid) [4].

Most herbal medicines must undergo physical and/or chemical pretreatment processing that are essential for preservation, detoxification, or enhancing efficacy. Improper processing can lead to adverse effects and toxicity. Basic processing includes washing, drying, or slicing of the plant material to clean the herbs and improve storage time. Additional processing such as sun drying, roasting, wine frying, vinegar frying, steaming, fumigation, boiling, or steaming is used to modify the therapeutic effects (detoxify, increase potency), alter bioavailability, or preserve active ingredients. Herbs contain multiple compounds, many of which may not be identified, and chemical fingerprinting is in the early stages and has not been done for most herbs. This makes standardization in terms of active constituents of herbal medicines a challenge [5, 6]. Some herbal medicines can be produced to contain a standardized amount of a key component or class of components, such as ginsenosides for ginseng products or silymarin for milk thistle products. However, even when such key compounds have been identified and a standard content is agreed upon, there is no guarantee that individual commercial products will contain this. That is because a plant’s environment can significantly affect the phytochemical profiles and efficacy of the herbal medicine produced. Herbal extracts can be variable from year to year and may be significantly affected by temperature, drought, or flood as well as by geographic location. Systems have been developed, over many years, so that herbal toxicities are rare and have been largely eliminated if prescribed and taken appropriately.

Doctors using herbal medicines want to be confident that the products they are prescribing to their patients are safe and contain what is on the label whether it is a specific herb or a particular amount of an herbal component.

Quality Control of Herbal Medicines

The quality control of herbal medicines is of utmost importance for herbal prescribing as it has a direct impact on their safety and efficacy. Developed countries have specific GMP based regulatory guidelines for the production and quality control of herbal medicines and herbal-based products. GMP regulations outline the process of setting and agreeing on technical standards. Herbal manufacturers are required to follow these standards to ensure the quality, safety, efficacy, and reproducibility of herbal medicines or herbal derivatives they sell [7, 8]. One of the most important steps in GMP is record keeping on the individual species of plants used, the part of the plant used (this greatly influences the concentration of active constituents), locations and conditions of cultivation, harvesting methods, proper processing, methods of extraction of active ingredients, and storage. GMP quality control standards apply to the production of herbal medicines as well as those imported for sale and also include testing for adulteration or substitution with conventional drugs, microorganism, chemical (e.g. pesticides), and heavy metal contamination. Sanitation and hygiene of herbal medicine production is also emphasized. In addition, they perform biochemical profiling (herbal authenticity) to ensure that the herbal products are consistent [9]. Methods to identify and ensure purity of the herb involved include thin layer and high-performance thin layer chromatography (HPLC), near-infrared spectroscopy, mass spectrometry, biochromatography (combines human red cell membrane extraction and high-performance liquid chromatography (HPLC) to screen for active constituents in herbs) and most recently DNA finger printing [9, 10]. DNA barcoding, which makes use of short, standardized regions of the genome as species “barcodes” is a DNA Sanger sequencing-based targeted approach appropriate for testing single ingredient herbal products with allergic potential, known or suspected toxicity, negative interactions with other herbs, supplements or prescription medication but may also detect some undeclared species. DNA identification of herbals was recently adopted by the British and Chinese national pharmacopoeias, which provide multi-taxa identification by using the DNA of different origins extracted from complex herbal mixtures and matrices. False negatives could occur if the DNA tested was degraded or lost during post-harvest processing or manufacturing [11, 12].

Origin of Herbal Medicines

Not all herbal medicines are herbal in nature and the inclusion of certain species of plants and animals in herbal medicines is illegal. Most herbal medicines are plant-based; however, some herbal medicines contain components of animal origin (horns, insects, shells, bone, antlers, minerals, etc.). However, in the past specific species of animals have been used to produce herbal medicine products to the extent that they have become endangered (e.g., tiger bone, rhinoceroses’ horn). The Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) was instituted in 1973 and is an international agreement between governments [13]. CITES, regulates the international trade of certain animal species, which are endangered or threatened with extinction if their exploitation is not halted. The goal of CITES is to ensure that international trade of these species of wild animals and plants does not threaten their survival. CITES regulates international trade of over 36,000 species of plants and animals, and their permit system seeks to ensure that international trade in listed species is sustainable, legal and traceable. National Laws for implementing CITES empowers government officials to act, regulates human behavior and articulates policy in relation to conservation and trade in wildlife. One of the species protected by the CITES has been detected using DNA barcoding and metabarcoding in commercial products. DNA trace of the snow leopard, which is an endangered species with the highest level of trade restriction has been identified using this method [14]. As the use of herbal medicines has become widespread for the treatment and prevention of diseases in humans, a similar trend has occurred in the veterinary field. As owners use herbal medicines for themselves, they want the same medicinal treatments for their beloved pets. It is imperative that veterinarians using herbal medicines know what herbs are potentially toxic or known to be toxic. Experienced herbalists are educated as to what these herbs are and what combinations are to be avoided. As previously described, adverse reactions or toxicity of herbal medicines occur for a variety of reasons. One of the most important and commonly seen in veterinary medicine is the use of herbal medicines without proper diagnosis by a trained herbal medicine practitioner. Experienced herbal practitioners know most diseases can be caused by several different patterns and each will have a unique treatment. Using the wrong herbal therapy for a condition can cause potential adverse effects.

Regulation for Herbal Medicines

All developed countries have regulatory bodies to ensure the quality and safety of herbal medicines and herbal products, and have developed similar GMP guidelines [15]. Regulation of herbal medicine and products in the United States, falls under the Dietary Supplement Health and Education Act (DSHEA) of 1994, any herbal medicine, supplement or herbal extract, is classified as a dietary supplement [8].This means that the herbal medicine manufacturer is responsible for determining that the dietary supplements produced are safe and any representation or claims made about them have adequate evidence to show that they are not false or misleading. GMP are used as per the FDA and are similar to those used for the manufacture of drugs [16–18]. GMP regulations in the US require that manufacturers, processors, and packagers of herbal medicines, medical devices, food products, and blood/blood products take specific measures to ensure that their products are safe, effective and to prevent contamination and processing errors. Manufacturers or distributors of a supplement with new herbal components that was not marketed in the United States before 1994, may be required to go through a premarket review for safety data. Also, all foreign herbal medicine producers/companies must follow the FDA’s GMP regulations. It is forbidden to label any herbal medicine product, sold as a dietary supplement in the United States, or suggest in any of its packaging that it can diagnose, treat, prevent, or cure a specific disease or condition without specific FDA approval.

Japan: In Japan, Kampo is regulated as part of the Japanese national health care system by the Ministry of Health, Labor and Welfare (MHLW) [8, 19

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