Read this article to learn about the antitumour agents produced in plant tissue culture.
Plants have been used in the treatment of cancer for over 3500 years. But it is only since 1959 that a concentrated systematic effort has been made to screen crude plant extract for their inhibitory activity against tumour systems.
Under the programme sponsored by National Cancer Institute, USA, around 2, 00,000 plant extracts from 2,500 genera of plants have been screened.
The number of medicines used in chemotherapy is around 20. These comprise the synthetic drugs and drugs obtained from plants. A large number of plant products have been shown to possess cytotoxic or anti-neo-plastic properties (Table 29.8).
Lomax and Narayanan (1988) of the National Cancer Institute (NCI), LTSA have presented a list of potent antitumour agents of interest to the Institute, which are at a developmental stage and the clinical trial level. Information about the new compounds of cancer therapy can be obtained from NCI, USA. The institute also helps in evaluating the chemicals against experimental tumours. Plant tissue culture provides an excellent system to produce such compounds in controlled conditions and to study their production, regulation, biosynthesis and bio-transformation. Unavailability of pure compounds in sufficiently large quantities is a limiting factor in their evaluation on animal systems. The drags are cleared for human consumption only after extensive clinical trials to evaluate their efficacy and side effects.
Anti-tumour compounds produced using various techniques of plant tissue culture are presented in Table 29.8. As stated earlier, production of secondary metabolites in the cultures is very low compared to the parent plant of the same species. Therefore, it is desirable to apply various factors to optimize the product yield and use special techniques for obtaining high-yields. These techniques were helpful in increasing the production of ellipticine, podophyllotoxin and tripdiolide in the cultures of Ochrosia elliptica, Podophyllum peltatum and Tripterygium wilfordii, respectively.
Among the anticancer agents of natural origin, vincristine, vinblastine, podophyllotoxins and taxol are currently used clinically. All these products are in great demand, production is low, difficult to isolate and purify and hence very high cost forced the world scientific community to search for alternative means of these drugs production.
If newer methods are available it will not only reduce the cost of drug but also relieved the pressure on plants which have become endangered because of over-exploitation, e.g., Taxus and Podophyllum. Therefore, efforts are being to develop efficient protocols for large scale multiplication of endangered medicinal plants like Podophyllum and Taxus and toprotect the habitat to conserve the plants in situ. The conservation programmes in different countries are part of global efforts to save medicinal and other plant species from being extinct.