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Principe (1989) reported that pharmaceutical companies have shown decreasing interest in the development of new plant products in favour of molecular biology and biotechnology applications to micro-organisms. However, some others in the industry believe that plant based resources will regain their importance. This hope has been bolstered by the much publicised prospecting agreement between pharamaceutical giant Merck and the Costa Rican National Institute for Biodiversity (Laird, 1993).
Although research based on micro-organisms to synthesise therapeutically active chemical compounds is promising, several limitations have to be borne in mind (Principe, 1989). The steps of identifying the chemical structure required to achieve a given effect and creating a proper genetic code for this structure, are the most difficult stages of drug development for which plant based genetic material appears to be better than micro-organisms. Genetically engineered micro-organisms can substitute only for some of the plant based chemicals. The vast majority of plant based chemicals have not been successfully synthesised (Principe, 1989).
Many consider that plant based drug resources have been exhausted in the early part of this century (Findeisen, 1991). However, the discovery of vincristine in Catharanthus roseus, reserpine in Rauvolfia serpentina, taxol in Taxus baccata and Taxus wallichiana, camptothecin in Camptotheca acuminata and Nothopodytes foetida, etc., have changed the direction and tempo of screening plants for drugs. This phase almost halted by the 1970s with a large scale failure to discover any ‘blockbuster’ drug from plant sources. Currently, once again, there is some considerable revival of interest in plant based drugs. Interest in plant based drugs has thus been going in cycles, or more precisely in spirals, reaching a similar situation at a different point in time.
Added to the problems outlined above, there are legal difficulties related to land rights, plant rights, patenting, etc. Patenting has to relate to the process of manufacture (and not the product) or to some uncertain anticipated value because biological organisms or natural compounds per se cannot be patented. At the present moment, material and intellectual property rights are in a fluid state all over the world, but more particularly in India. Indications are that, in due course of time a clear cut policy and rules would emerge, when there would be more incentive for personal initiative and effort.
Notwithstanding all the difficulties, there has been a fresh revival of interest in plant based drugs in the last ten years or so. This is mostly based on improved techniques of purifying, analysing and assaying samples and use of robots for continuous assay of material. Another factor, the consumers’ demand for natural products, has also contributed to the new herbal culture. As a result, internationally, the US National Cancer Institute, Monsanto, Smith Kline, Merck and Glaxo have resumed plant screening on a fairly large scale (Reid et al., 1993). Affymax and Shaman are new US companies which deal with drugs solely from natural products with emphasis on traditional medicine.
The significant point regarding medicinal plants is that they are used to support arguments for conserving entire biological resources in the third world, though the actual relevance is difficult to justify. On the one hand it is argued that if genetic engineering procedures become more successful, they would replace plant based research. On the other hand it is said that since the knowledge of medicinal plants is very limited, not paying adequate attention to them the soonest, may prove disastrous in the long run, as they may be lost for ever.
Evenson (1991) distinguishes between a) general strategic research for new resources that justifies the maintenance of most biological materials, and b) specialised research for genetic material to meet specific needs, which justifies the collection and preservation of genetic resources.
Ascribing economic value to medicinal plants can be done on two bases (Pearce and Moran, 1994). The first relates to the existing values which, in turn, are for commercial drugs and for traditional medicine. The other relates to the option value of plants, that is the extent to which conservation is required to protect the future use values. Unfortunately, option values depend on a critical judgement and the correctness of this judgement, on which a species is to be conserved.
ECONOMIC VALUE OF PLANT BASED DRUGS
The introduction of a single new synthetic drug into the market would take about 10 to 15 years of time and about US$100 to 300 million, in expense (Abelson, 1990). Plant based drugs would take a comparatively much less time and expense than synthetic drugs. Hence, plant based medicines would be far inexpensive, unless the market prices are inflated by other considerations.
The economic evaluation of plant based drugs is different from that of the raw source material of medicinal plants. For both, much depends upon the demand and the supply potential. For medicinal plants, the source material, the land use value, costs of collection/cultivation, costs of preparation, packaging and transport are the criteria. For plant based drugs, the costs of discovery, clinical testing, processing, packaging and marketing add up. In most countries, there are plant collecting agencies, with one to several manpower capabilities. There are also large internationally operating plant gathering agencies which in turn may use the local suppliers. Usually payment of royalties is not involved in this process, except occasionally as in the case of the US private company Biotics, which has royalty agreements with the companies to which it supplies raw material. In some cases, even the countries are also involved. This is in tune with the spirit of the recommendations of the Rio Biodiversity Convention. While there are many variations in royalty sharing, Findeisen (1991) reports that royalties are negotiated on the basis of the value of the drug to the drug companies, with figures of royalty varying from five to 20 per cent. Ignorance, uncertainty, essentiality,
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