| All over the world at present there is a great activity | | | | It is noteworthy that all the early investigations into |
| as scientists investigate plants, micro-organisms, | | | | the chemicals found in plants utilized those with |
| marine creatures and many other forms of life for | | | | medicinal activity. It was found that, in many cases, |
| biological activity. There is a desire to find out more | | | | the activity of the crude plant extract could be |
| about the interactions between one organisms and | | | | reproduced by an equivalent dose of the isolated |
| another which can be attributed to the chemical | | | | active constituent and this laid the foundation for the |
| substances present in at least one of the species | | | | modern scientific presentation of orthodox |
| concerned. The area where activity has been | | | | pharmaceuticals. These active constituents of one |
| greatest is the effect of extracts from the flowering | | | | molecular type, 'the single chemical entity', could |
| plants on human physiology and human pathogens, | | | | either be isolated from natural sources or |
| since this is very relevant to the discovery of new | | | | synthesized, and was incorporated into a dosage |
| drugs for treating diseases of human beings and | | | | form. |
| other mammals. | | | | As the herbal drugs contain so many chemical |
| There are mainly two reasons for interest in natural | | | | compounds, it is essential to separate out those |
| products. Firstly, the use of medicinal plants such as | | | | compounds, which are responsible for therapeutic |
| phytomedicines, dietary supplements, food and | | | | effect and are called active constituents. Some |
| beverage ingredients and traditional medicine, this | | | | important chemical substances found in plants are |
| segment is growing rapidly. Secondly, natural products | | | | alkaloids, flavonoids, saponins, glycosides, essential |
| continue to remain an important source of new drug | | | | oils, fatty oils, resins, mucilage, tannins, gums and |
| discovery. It is now increasingly accepted worldwide | | | | others. These potent bio-active compounds which |
| that screening natural products is the more effective | | | | are found in medicinal plants are most commonly |
| strategies for discovering new chemical entities as | | | | used for the therapeutic purpose or as a precursor |
| product libraries have a broader distribution of | | | | for the synthesis of useful drugs. The active |
| molecular properties such as molecular mass, | | | | principles differ from plant to plant due to their |
| octanol-water partition co-efficient and diversity of | | | | biodiversity and they produce a definite physiological |
| ring systems when compared to synthetic and | | | | action on the human body. |
| combinatorial counterparts. | | | | Many methods have been devised whereby the |
| Most of the earliest pharmaceuticals were plant | | | | activity of a compound or extract can be tested |
| materials. The obvious effect on human health and | | | | scientifically. In the case of possible new drugs, these |
| activity following the ingestion or application of plant | | | | methods range from the clinical testing of volunteers |
| products is known in most societies and the | | | | to cell-free enzyme systems and receptor binding |
| consequent use of plants for treating disease | | | | assays. The consequence is that, once having found |
| commenced before written history. Similar use for | | | | activity in the extract from plant, there is a desire to |
| getting rid of pests have also been known and | | | | find out the compounds that are responsible for the |
| employed for a very long time. This pragmatic use | | | | activity. It is interesting and intellectually challenging to |
| under laid the development of Modern Botany, | | | | isolate novel chemical compounds. |
| Taxonomy and Chemistry as science progressed. | | | | |