Standardization of Herbal Medicines free essay sample

Herbal medicine is the most primitive traditional approach to the treatment of diseases and ailments. It is called herbal medicine because it involves the use of plants or plant parts. There is no doubt that herbal medicines provided the first basis for therapeutics before the development or advent of orthodox medicine. Despite the fact that, over the years, chemists have synthesized a large number of chemical substances, many of which have proved useful in modern therapeutics, plants still remain potential sources of useful products. Although the medicine prescribed may contain only one single active item, it is often a mixture of many components. Thousands of herbal medicines are used by peoples from every culture and various indigenous medicines are gradually being introduced into modern therapeutics. In developing countries about 80% of the people, especially the rural population, rely on traditional medical remedies for their health care needs. In developed countries, there has been a resurgence of interest in herbal medicines due, to a large extent, on the preference of many consumers for products of natural origin. In addition, manufactured herbal medicines from their countries of origin often follow in the wake of migrants from countries where traditional medicines play an important role. It is important however, to distinguish between herbal medicine supplied by a â€Å"qualified† medical practitioner as a result of a consultation and those herbal remedies (in the form of â€Å"teas†) freely available to the public for self-medication. DEFINITION: According to the World Health Organization (WHO), herbal medicines should be regarded as â€Å"finished, labelled medicinal products that contain as active ingredients aerial or underground parts of plants or other plant materials or combinations thereof, whether in the crude state or as plant preparations. Plant material includes juices, gums, fatty oils, essential oils and any other substances of this nature. Herbal medicines may contain excipients in addition to the active ingredients. In some countries, herbal medicines may also contain, by tradition, natural organic or inorganic active ingredients which are not of plant origin. Medicines containing plant materials combined with chemically defined active substances including chemically defined isolated constituents of plants are not considered to be herbal medicines†. Problems associated with herbal medicines: One of the major criticisms levelled against herbal medicines is that they are neither standardized nor are they dispensed to patients in specified doses or in strictly regulated quantities. However it is becoming increasingly clear that the standardization of herbal medicine entails much more than just specifying the amount of the medicine to be taken by the patient. It is also important that every stage of the production process should be standardized. Prior to the current availability of mass- marketed herbal medicines and dietary supplements, herbalists and patients prepared their own herbal medicines. Often the herbal ingredients were grown and obtained locally and compounded by hand into a particular formula or concocted into a simple infusion or decoction. Each product was therefore a unique formulation (because different individuals of the same plant species, grown in different soils, at different times of the year, harvested on different days and even stored in different ways, will all contain different amounts of the active medicinal substance). onsequently, doses and effects were acceptable even if variable and inconsistent. However, the pharmaceutical industry cannot function as big business if it has to tailor- make drugs for localities and small groups of people. Numerous herbal products are now grown worldwide and are distributed internationally. Although many ethical manufacturers are currently producing high quality products that are based on careful identification and assays for impurities, it is often difficult to determine which brands and products meet even basic quality standards. This is because standardization practices, if at all in place, can vary considerably between manufacturers. It is usual to find that different marketed brands may vary substantially not only in the quality and quantity of active herbal medicines but also in the absolute or relative concentrations of the chemical constituents in the different products. Laboratory analyses of different brands of herbal medicines show that: important constituents may vary by 5-, 10-, or even 40- fold. Some contain no labelled products at all. There have been reports of substitution or contamination of the declared ingredient with toxic herbs that may be dangerous; presence of environmental pollutants (pesticides, toxic metals, microorganisms etc) and adulteration with drug products. It is also reasonable to assume that, as with pharmaceutical drugs, misrepresentation in herbal preparation marketing may increase in the coming years unless vigorous efforts are made to check such unwholesome practices. Prospects: The art and science of herbal medicine has become more sophisticated. As herbal medicines become increasingly packaged and advertised to compete with pharmaceutical drugs, consumers and healthcare providers equally expect them to meet comparable quality standards. Standardization of herbal medicines: Simply put, it means the process of recommending a set of pharmacognostic , chemical, biological and pharmaceutical standards adequately controllable, which could form an official monograph or part thereof for a proposed plant drug preparation. Standards for herbal medicines, either when used as a single constituent or in combination, should include identity, quality and purity, to ensure, as far as possible, uniformity in physical properties and active constituents and provide all other information regarding the distinguishing characteristics. Since it is easier to standardize a single component than a multi-component herbal medicine, the best approach for standardization is to provide preliminary standards for all the individual plant components at crude drug level. Thereafter, those standards that are not significantly affected by the mixture technology can be applied to the standardization of the finished products. Moreover, a multi-component herbal medicine whose individual plant components have undergone standardization at crude drug level can be further standardized as a finished herbal medicine using the general mixture characteristics such as chromatographic fingerprinting in a given chromatographic system or a general colour of spectrophotometric profile. PHARMACOGNOSTIC STANDARDIZATION: Fortunately all crude botanicals can be subjected to a pharmacognostical evaluation/ examination involving authentication, freedom from impurities, simple extractive tests and general quality control before they are extracted. This done and within the limits of variations due to chemical races, ontogeny and geographical source, all preparations made from different consignements, by sound manufacturing methods, should be generally acceptable and of uniform quality. The botanical information on the crude plant material should be comprehensive enough to eliminate the risk of preparing sub-standard or adulterated drugs. The information should give full details about: Identity: A formal description should give details of botanical name, family and authentication by a qualified taxonomist; a comprehensive description of the plant/ plant part used, the date of collection, harvesting and post harvest treatment, data from field investigations, ethnobotanical studies, the most essential characteristics of the plant components including organoleptic, macroscopical and microscopical (both qualitative and quantitative) characters. It is advisable that a voucher specimen representing each lot of the plant material which has been processed should be appropriately kept and assigned a voucher number. Information on moisture content, solubility, acidity of water extract, soluble and insoluble extractive values, ash values, limit tests to determine foreign matter, impurities and microbial counts, marker compounds and results of some definite qualitative tests should also be provided. CHEMICAL STANDARDIZATION: This standardization implies that the preparation contains a designated amount or percentage of the therapeutically active component . However standardization of specific active constituents within herbal medicines, unlike that of drug products with a single chemical entity, is complex and unreliable. Herbal medicins may contain hundreds of bioactive chemicals and the contributions of individual compounds responsible for the overall therapeutic activity are usually unknown since additive and synergistic activity of the constituents may be required for effectiveness. Therefore in the case of herbal medicines, although standardization of chemical components may be used to assist batch-batch replicability, the process fails to provide reliable controls for pharmacological activity. Nonetheless, the ultimate goal is to identify and characterize the structures of the pharmacologically active constituents including absolute and relative percentage concentrations, their detection, and solubility etc. Usually a method of the identification and assay of the plant material and, if possible, quantification of the finished product should be prepared. PHARMACEUTICAL STANDARDIZATION: Galenicals must be prepared by following standard procedures such as maceration, percolation, decoction etc. There is need to standardize the amount of extract or active component in the finished product (tablet, capsule, pill etc) to ensure that each batch of the formulation complies with the composition stipulated. BIOLOGICAL/PHARMACOLOGICAL STANDARDIZATION:Fortunately many of the plants used in herbal medicine contain principles whose effects can be demonstrated pharmacologically and the action of the whole plant extract can usually be related to that of the isolated constituents. However, for most herbal medicines, it is not possible to demonstrate or evaluate their pharmacological activity and the situation is compounded by the frequent use of a number of ingredients in combination whose active constituents have not been elucidated. In such instances, there is no means of assessing therapeutic activity except by the use of a biological assay whenever and wherever feasible. Extensive pharmacological studies should be carried out on all fractions to determine possible side-effects. Where there are no existing laboratory models for a particular disease, a suitable model should be developed. MICROBIOLOGICAL STANDARDIZATION:Herbal medicines intended for antimicrobial use should be subjected to standard antimicrobial protocols for the specified disease. For other herbal medicines, the microbial load should be determined and limits established in accordance with the broad WHO guidelines on purity. TOXICOLOGICAL STANDARDIZATION:A number of cases of toxicity arising from the over-consumption of herbal remedies have been reported, the principal danger arising from the uncontrolled supply and administration of these products. It is therefore advisable to ensure that the product is non-toxic. To establish this fact, tests for chronic and acute toxicity should be carried out on laboratory animals before proceeding to tests on humans according to laid down international procedures for toxicological evaluation. The therapeutic index of the drugs should also be established. CONCLUSION:Currently there are no government regulations that assure manufacturing standards and quality control other than the Good Manufacturing Practice (GMP) regulations required for foods. Therefore all procedures for the manufacture and assessment of herbal medicines should comply with this protocol. The in-house operations should be controlled to eliminate errors in manufacturing and check excessive variability which may lead to the production of poor quality herbal products. There should be consistency in the manufacturing process so that variations in the content of identified marker or active constituent will be minimized. This will ensure consistentency in the quality of the herbal product from batch to batch. Physical and chemical stability of the herbal medicine in its final packaging/ container should be tested under defined storage conditions. The shelf-life should be determined. Detailed methods of preparation or manufacture for the particular preparation, including composition or concentration of active substances per unit volume or weight as well as its preservation and stability profile should be included. Consumers should recognize that no government agency currently regulates the production and quality of herbs and should exercise discretion in selecting any herbal medicinal product. Scientific professionals should learn to keep an open mind and accept that, although a substance may lack evidence of efficacy, this does not mean that it is ineffective or that it cannot be useful in any clinician-patient interaction. The herbal industry should police itself and try to eliminate fraudulent or unacceptable marketing. CHEMICAL RACES: The on-going intensive chemical investigations for substances of medicinal value or suitable precursors of therapeutic active substances from plants have revealed that, although some plants exhibit similar phenotypes, they differ in their genotypes and as such are identical in external appearance only but differ in their chemical constituents/composition. Such plants are referred to as chemical races/physiological races/chemical varieties. In a few cases the different chemical races can easily be identified by visual means eg the presence or absence of particular anthocyanin pigments in certain flowers can give rise to coloured or colourless/white forms. In most cases, however, extensive analyses as well as horticultural work over many generations are required to demonstrate conclusively and exclusively that the observed differences are truly genetic in nature and not merely due to diurnal, seasonal and/or environmental variations. The existence of chemical races has been demonstrated in the following: 1. Species of Duboisia : They contain the tropane alkaloids hyoscine, hyoscyamine,nor-hyoscyamine etc but the proportion of any one alkaloid in the total alkaloid mixture may vary greatly due to seasonal and environmental factors. On the other hand, it has been found that within a given specie, there may exist various alkaloid types eg nicotine and nor-nicotine have been reported in species of D. yoporoides and D. leichhardti. These observations have led to the conclusion that in this genus two distinct chemical races exist namely: (a) Different alkaloid-types within a specie (b) Different alkaloid-types among hybrid phenotypes. 2. Among the Dryopteris: The presence or absence of phloroglucinol derivatives has been used as the basis for distinguishing chemical variations among species of Dryopteris especially D. spinulosa. 3. Purgative drugs: Although the therapeutic activity of purgative drugs is due to the complex mixture of 1,8-dihydroxy-anthranol derivatives, their glycosides and free anthraquinones, the relative proportions of the mixture components depends not only on time of collection, age of the plant, drying conditions and geographical sources but also on genetic factors. Consequently chemical races have been found which vary for (high- and low- yielding total anthraquinones) and others (in their rhein/chrysophanol ratio). 4. From polymorphous Strophanthus sarmentosus four chemical variations have been identified namely sarmentogenin-, sarmutogenin-, sarverogenin- and low- glycoside producing forms 5. As early as 1830, the release or otherwise of hydrocyanic (prussic) acid by cyanogenetic/cyanophoric glycosides on hydrolysis has been used to separate the sub-families of the Rosaceae. At the species level it could denote varieties or different chemical races of the same species eg Prunus amygdalinus yields both bitter (var. amara) and sweet (var. dulcis) almonds. In conclusion, chemical races can occur in plants either naturally or be brought about by plant breeding techniques. However obtained, they can be used for various purposes 1. Improve the therapeutic value of a drug (either by adjustment of the individual constituents or by increasing the overall yield). 2. Serve as tools in the elucidation of the later stages of the biosynthetic process. 3. Help in chemotaxonomic studies to determine the exact positions taxa should occupy with respect to the taxonomic hierarchy already established by morphological characters.