The so-called “green wave”, triggered by a growing ecological awareness, has resulted in an increased interest in herbal formulations throughout the world, particularly in the last decade. The consumption of medicinal plants has almost doubled in the West during that period. The efficacy of a number of herbal formulations has been tested by valid phytopharmaceutical techniques and the number of plant-based drugs or health foods has increased steadily to meet the growing demand. Over the years a new relationship between phytochemists and pharmacologists has accordingly developed which, in many cases, has proved to be very productive.
Unfortunately, despite recent advances in chromatographic and spectroscopic techniques and the rich tradition of the use of herbal medicines, the majority of natural product chemists in developing countries are involved in empirical phytochemical practices and very little effort has been directed towards isolating the bioactive chemical constituents from the natural sources. This is due to the lack of expertise and infrastructure for biological screening and the often long waiting times required for such screening if samples are sent to other pharmacology laboratories. It is therefore highly desirable to establish in-house bioassays in phytochemistry laboratories which are inexpensive, rapid and do not require a specialized knowledge of biochemistry, biology or pharmacology. A number of phytochemical laboratories in the West have therefore established simple “bench-top” bioassays which can be carried out by non-specialists. The results obtained from such processes have strongly justified such a multidisciplinary approach. It is hoped that this manual of bioassay techniques will fulfill the need for a comprehensive text and prove useful to a large number of natural products chemists from around the world.
Bioassays can be divided into various broad groups based on the target life forms on which they are carried out. These could be:
1. Whole animals
2. Isolated organs of vertebrates
3. Lower organisms e.g. fungi, bacteria, insects, molluscs, lower plants, etc.
4. Cultured cells (such as cancer cells) and tissues of human or animal origin
5. Isolated subcellular systems, such as enzymes, receptors, etc.
The goal of an activity-directed isolation process is to isolate bioactive compounds which are capable of curing or alleviating a human or animal ailment and which can either be ultimately developed as established drugs directly or which can provide interesting structural leads. The process of drug development is long, tedious and expensive, requiring a multidisciplinary collaboration be-tween botanists, pharmacognosists, chemists, pharmacologists and toxicologists, and clinicians. Simple and rapid bioassays can serve as starting points for such multidisciplinary efforts directed at drug discovery.