Phytotherapy and quality of herbal medicines
Introduction
The sale of herbal medicines has increased considerably over the last 10 years in the industrialised countries. This growing trend to use herbal medicines to treat a wide range of problems (from insomnia, anxiety, obesity, bronchial asthma, constipation, gingivitis, Vincent’s infection, eczema and varicosity to immunodeficiency syndrome) has been promoted by: (i) the development of new diseases, with severe complications, for which there is still no appropriate treatment; (ii) the belief that herbal remedies are innocuous, in contrast to conventional drugs; (iii) the idea that what is natural can only be good; (iv) the special attention that ecological movements give to herbal medicines in Western countries; and (v) the belief that herbal medicines are naturally superior to synthetic drugs [1], [2], [3]. Another factor can be found in the progress achieved in the field of production and conservation of herbal medicines. Today the possibility of cultivating medicinal plants, sometimes genetically improved, enables to introduce on the market plants which are rich in desirable active compounds.
Apart from the advantages which cultivation can offer (Table 1), the development of modern methods of processing and preserving the raw material of medicinal plants (dehydration through drying in vacuum packs, liyophilisation, etc.) helps to maintain their quality for a longer time. However, a vast number of herbal medicines used in Western countries have not been submitted to rigorous scientific testing and their quality is extremely variable. In addition, the components of these herbal medicines are not rigorously substantiated. Thus, instances of efficacy and toxicity have recently surfaced with several commercially available herbal medicines, challenging the effectiveness and safety reputation of phytotherapy [4], [5], [6].
Section snippets
Toxicity of herbal medicines and importance of the pharmacovigilance
The potential toxicity of herbal medicines is not new. In several countries, like Asia and Africa, where herbal medicines are commonly used, it is well known that some plants must be used with caution because they may be toxic for liver (pyrrolizidine alkaloids, apiole, safrole, lignans, etc.), kidney (terpenes, saponins), skin (sesquiterpene lactones, furanocumarins, etc.) and other tissues [7], [8], [9], [10], [11], [12], [13]. It is also known that many plants produce toxic substances
Standardisation and efficacy of herbal medicines
It is now well known that the therapeutic efficacy of herbal medicines is not influenced by a single group of compounds (i.e. alkaloids in belladonna). Therefore, the chemical analysis should not be confined to a single product but extended to several groups of constituents in order to obtain a characterisation as complete as possible.
For example, belladonna, the dried leaves of Atropa belladonna, contains propane alkaloids, flavonoids (quercetin, kaempferol, glucosidic flavones), chlorogenic
Conclusions
Herbal medicines are becoming popular in developed countries as a result of dissatisfaction with conventional medicines. There is a wide belief that herbal preparations, being ‘natural’, are intrinsically harmless. Their effects are generally not due to their natural origin but rather to the pharmacological characteristics and dose levels of their active constituents. The chemical analysis of the constituents is the most important part of the standardisation. However, herbal medicines can be
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