Chapter 1 Importance of plants in modern pharmacy and medicine

Importance of plants in modern pharmacy and medicine

https://www.elsevier.com/books/fundamentals-of-pharmacognosy-and-phytotherapy/heinrich/978-0-7020-3388-9

Aims and definitions

This introductory textbook aims to provide a scientific basis for the use of plants in pharmacy (pharmacognosy) and also to describe the main characteristics of herbal medicines (herbal medicinal products, herbal remedies, phytomedicines) and their clinical uses [herbal medicine (UK), phytotherapy (Continental Europe)]. There is also an overview of some of the historical aspects of medicinal plant use in different societies (ethnobotany, ethnopharmacology) and of the role of plants in a variety of popular ‘non-scientific’ medical systems (traditional medicine).

Pharmacognosy (derived from Greek pharmakon, ‘remedy’, and gignosco, ‘knowledge’) is the science of biogenic or nature-derived pharmaceuticals and poisons. It deals with all medicinal plants, including those yielding complex mixtures, which are used in the form of crude herbs (comminuted herbal substance) or extracts (phytotherapy), pure compounds such as morphine, and foods having additional health benefits only in the context of having preventive effects (nutraceuticals).

Types of drugs derived from plants

Herbal drugs derived from specific parts of a medicinal plant

Botanical drugs which form the basis for herbal remedies or phytomedicines include, for example:

• the herb of St John’s wort (Hypericum perforatum), used in the treatment of mild to moderate depression

• the leaves of Ginkgo biloba, used for cognitive deficiencies (often in the elderly), including impairment of memory and affective symptoms such as anxiety

• the flower heads of chamomile (Chamomilla recutita), used for mild gastrointestinal complaints and as an anti-inflammatory agent

• the leaves and pods of senna (Cassia spp.), used for constipation.

From the perspective of pharmacognosy and rational phytotherapy, such products lie alongside, and in some cases are, conventional pharmaceutical medicines. Herbal medicines are often considered to be part of complementary and alternative medicine (CAM), and the use of herbal medicinal products (HMPs) and of CAM has increased across the developed world.

Natural products or compounds isolated from nature

These are pure chemical entities, often used in the form of licensed medicines. They are sometimes produced synthetically and referred to as ‘nature identical’ (if that is the case), but were originally discovered from plant drugs. Examples include:

• morphine, from opium poppy (Papaver somniferum), used as an analgesic

• digoxin and other digitalis glycosides, from foxglove (Digitalis spp.), used to treat heart failure

• taxol, from the Pacific yew (Taxus brevifolia), used as an anticancer treatment

• quinine, from Cinchona bark (Cinchona spp.), used in the treatment of malaria

• galanthamine from Galanthus and Leucojum species, used in the management of cognitive disorders.

Nutraceuticals or ‘functional foods’

Many foods are known to have beneficial effects on health. Examples include:

• garlic, ginger, turmeric and many other herbs and spices

• anthocyanin- or flavonoid-containing plants such as bilberries, cocoa and red wine

• carotenoid-containing plants such as tomatoes, carrots and many other vegetables.

Use of herbal medicines

The use of these remedies is extensive, increasing and complex. In several surveys 20–33% of the UK population claimed to regularly use CAM alone or in addition to orthodox or conventional medicine and treatments. In the UK, usage is particularly frequent amongst those who are over-the-counter medicines-users. There is not, on the whole, a wide understanding of what herbal medicines are (or are not) (IPSOS-MORI 2008). Healthcare professionals and students also commonly use such products. Forty-three percent of students at a University School of Pharmacy reported using at least one type of CAM during the last 12 months (Freymann et al 2006).

In the United States, approximately 38% of adults and approximately 12% of children are using some form of CAM (NIH/NCCAM). Kennedy et al (2008) showed that in the preceding 12 months about 38 million adults in the US (18.9% of the population) used herbal medicines or supplements, but that only one-third revealed this use to their physician. Data for other regions are even more limited, but the usage of herbal medicines is widespread in countries like India, Indonesia, Australia and China, to name just a few.

In addition, market research data reveal high levels of expenditure on herbal medicines, although it is difficult to obtain precise figures for sales of such products since some are classed as food supplements and are sold through numerous outlets. For similar reasons, it is usually not possible to compare properly the estimates for expenditure on herbal medicines using different studies and in different countries. For 2009, it is estimated that the total value of the global market in herbal medicines was around $83 billion. In 2009 in the USA alone consumers spent an estimated total of $5 billion on herbal dietary supplements. In the UK in 2007, the market for herbal medicines was estimated to be almost £700 million, which, compared with many other European countries, is rather low. The European market for herbal supplements and herbal medicines is currently worth about $7.4 billion. Germany is the largest European market, with a 27% share, followed by France (24%), Italy (12%) and the UK (9%). The Indian healthcare market is valued at $7.3 billion, 60% of which is controlled by pharmaceutical drug manufacturers, while 30% is controlled by Ayurvedic medicine manufacturers; the Chinese market comes in at around $8 billion.

In most continental European countries, such phytomedicines are licensed medicinal products and are used under medical supervision. However, the widespread use of herbal medicines by the general public raises several important issues. Some of these relate to how individuals, whether consumers or healthcare professionals, perceive and use these preparations; other concerns relate to the quality, safety and efficacy of the herbal medicines themselves.

As part of the primary healthcare team, pharmacists, as well as nurses and general practitioners, need to be competent in advising consumers on the safe, effective and appropriate use of all medicines, including herbal medicines. Healthcare professionals also need to be aware of the products and healthcare choices that patients are making, often without their knowledge.

There are many reasons for the increased use of herbal medicines. These may range from the appeal of products from ‘nature’ and the perception that such products are ‘safe’ (or at least ‘safer’ than conventional medicines, which are often derogatorily referred to as ‘drugs’), to more complex reasons related to the philosophical views and religious beliefs of individuals.

In developed countries, most purchases of HMPs are made on a self-selection basis from pharmacies and health-food stores, as well as from supermarkets, by mail order and via the Internet. Normally, with the exception of pharmacists, there is no requirement for a trained healthcare professional to be available on the premises to provide information and advice. In any case, most HMPs can be sold or supplied without the involvement of a healthcare professional and several studies have confirmed that many individuals do not seek professional advice before purchasing or using such products, even when purchased from a pharmacy (Barnes et al 1998, Gulian et al 2002). Rather, consumers of HMPs tend to rely on their own (usually limited) knowledge, or are guided by advice from friends and relatives or the popular media. Consumers who do seek professional advice (e.g. from their pharmacist or general practitioner) may find that he or she is not able to answer their question(s) fully. In some cases this may be because the information simply is not available, but it is also recognized that, at present, many healthcare professionals are not adequately informed about herbal medicines, particularly with regard to their quality, safety and efficacy. This book attempts to redress that omission.

HMPs are used for general health maintenance, as well as for treating diseases, including serious conditions such as cancer, HIV/AIDS, multiple sclerosis, asthma, rheumatoid arthritis and osteoarthritis. Older patients, pregnant and breastfeeding women, and children also take HMPs, and this raises concerns because, as with conventional medicines, precautions need to be taken. For example, few medicines (whether conventional or herbal) have been established as safe for use during pregnancy and it is generally accepted that no medicine should be taken during pregnancy unless the benefit to the mother or fetus outweighs any possible risk to the fetus. Similarly, HMPs should be used with caution in children and the elderly, who, as with conventional medicines, differ from adults in their response to, and metabolism and clearance of drugs. The use of herbal medicines by patients who are already taking prescribed medicines is of particular concern as there is the potential for drug–herb interactions to occur. For example, important pharmacokinetic and pharmacodynamic interactions between St John’s wort (Hypericum perforatum) and certain conventional medicines have been documented (Williamson et al 2009