In the era of drug design by chemical synthesis aided by computational and combinatorial techniques, emphasis on the screening of natural products for new drugs by pharmaceutical companies decreased with greater reliance being placed on screening large ‘libraries’ or collections of synthetic compounds. Natural product extracts have been regarded by some as being incompatible with modern rapid screening techniques and the successful market development of a natural product derived drug as being too time consuming. Also taking out patents on natural compounds is usually more difficult than it is for synthetic substances. With the introduction of newer drugs obtained increasingly through biotechnological processes, it appeared that natural products no longer had any significant role in new drug development.

Advances in cell and molecular biology and the resultant biotechnological breakthroughs have brought about profound repercussions in all aspects of life sciences. Plant cell culture is one such biotechnological tool of growing plant cells, tissues or organs isolated from the mother plant on artificial media. It is an experimental technique through which a mass of cells is produced from the ex-plant tissue. Being unaffected by changes in environmental conditions, studies on production of useful metabolites by plant cell culture have been carried out on an increasing scale since the end of 1950s. Though their results stimulated recent studies on the industrial application of this technology, there are several hurdles to be overcome before successful utilization of this technology and not many drugs are being commercially produced this way today.

Similarly genetic engineering and recombinant DNA technology has made available novel therapeutic enzymes and human therapeutic proteins for the mitigation of several deficiency disorders. Likewise genetic engineering of bacteria or yeast to produce the complex SMs naturally biosynthesized by certain plant species is a difficult task because of the nature of SM biosynthesis. This is because SMs, unlike simple proteins, are not the products of single genes. Instead, they are often complex biomolecules, generally the end products of long, multistep, enzymatically catalysed reaction cascades, i.e., complex biosynthetic pathways involving multiple gene products. It would therefore be a difficult task to assemble and transfer all of the necessary biosynthetic machinery into a foreign microorganism and have it functional to achieve the desired biosynthesis. The greatest long-term potential of genetic engineering and related rDNA-based technologies lies not in the direct production of plant proteins, but in the improvement of the efficiency of the biosynthetic machinery of those plant cells producing extractable plant metabolites of interest. Therefore it is not a simple task to manipulate and genetically engineer plant cells at this level of organization and complexity.