Ethnopharmacology and natural product drug discovery remains a noteworthy hope in the current discovery of new drugs. Many modern drugs have origin in traditional medicine and ethnopharmacology. Ethnopharmacology is the use of tradition plant medicines as source of new drugs.
Traditional Indian Medicine - Ayurveda has a long history and is one of the great living traditions. Considerable research on pharmacognosy, chemistry, pharmacology and clinical therapeutics has been carried out on Ayurvedic medicinal plants. Several preclinical and clinical studies have examined cytoprotective, immunomodulatory and immunoadjuvant potential of Ayurvedic medicines. The ethnopharmacology knowledge, is holistic and systems approach supported by experiential base can serve as an innovative and powerful discovery engine for newer, safer and affordable medicines.
The Process of Modern Drug Discovery using Ethnopharmacology
The first stage should be the reported use of a natural occurring material for some purpose which can be related to a medicinal use. There must be an indication of a genuine effect and therefore, the material needs to be identified and characterized. It can be collected for test studies which comprises tests for relevant biological activity linked with isolation and structure determination of any chemical present that might be responsible. The active compounds are discovered by fractionation of the extract linked with testing for activity of each fraction until pure compounds are isolation. This is Bioassay-guided Fractionation. When the activities are proven, these compounds serve as leads to development of clinically useful products.

Information collection In-depth studies carried out by field workers in a particular community of a particular ethnic group on the use of plants and their material. This need frequent communication with the local population in their language. But an extensive knowledge of traditional medicines may reside with only a few people and a focus on this group would yield greater results. Some people fail to disclose this information because the knowledge may be exploited by companies with little or no return to the original owners. For example, African Prune Bark Pygeum africanum, used to reduce benign prostratic hypertrophy. It’s geographical source is Central African highlands.

Scientific investigation
Extraction: the extract should be similar in active ingredients and concentration to that obtained by the traditional process used. Simple extractions are done with hot water or a variety of other solvents, and additives or treatment of the material before use. Mostly, it is likely that fairly polar compounds will be extracted although the solubility of less polar substances may be elevated considerably due to solubilizing compounds, like saponins. For example, Artemisia annua, contains appreciable levels of major antimalarial sesquiterpene artemisinin, which on its own has very low solubility in water.
Tests for activity: this is mostly done by industrial and academic research groups, a particular bioassay or series of in vitro bioassays, designed on the basis of biochemistry or molecular biology of the disease. Ethno pharmacology has little relevance to the tests used except that it provides a number of screening samples selected on the basis of their traditional use for the disease. The biological effect may be essentially toxicological, e.g. use of poisoned arrows and so it is important to seek to ascertain the basis of the toxic effect. Most test systems for biological activity utilize in vitro systems using animal tissue, cultured cells, cloned receptors or enzyme systems. Some tests like bioassay-guided fractionation are used to carry out large numbers of tests using small amounts of material in a short time. It should be noted that biological testing for the traditional use may reveal a different but nevertheless interesting activity such was the case in the discovery of the anticancer compounds from Catharanthus roseus.
Chemical examination: this should be linked with tests for biological activity. Chemical examinations distinguished alkaloids, glycosides, flavanoids, tannins, latex and other molecules. Chemotaxonomic considerations can often provide a reasonable guess to the nature of the active components and ease their isolation. Insecticidal or anti-inflammatory activity noted in a member of the Asteraceae could be ascribed to the sesquiterpene lactones. The presence of naturally occurring compounds can be screened by the use of appropriate chromogenic reagents after separation using thin layer chromatography or liquid chromatography linked with mass spectroscopy.
Isolation: this is the separation of the active components from each other from the sample. This include:
- Distillation methods, e.g. steam and fractional distillation.
- Chromatographic methods, e.g. thin layer chromatography, high performance liquid chromatography, gas chromatography, affinity chromatography, gel filtration chromatography.
- Fractional crystallization
For example, steam distillation is used to separate aspirin from parahydrobenzoic acid. This is because aspirin has intramolecular bonds which are more volatile while parahydrobenzoic acid has intermolecular bonds.
Structural elucidation: This is the process of determining the chemical structure of a compound. For organic compounds, it will often involve the use of nuclear magnetic resonance spectroscopy (NMR spectroscopy). Other characterization techniques include mass spectrometry, infrared spectroscopy and X-ray crystallography.

Advantages of using ethno-pharmacological approach:
1. Safety and efficacy
The argument that usually supports the use of ethno pharmacological approach to obtaining new drugs is the fact that plant material has been in use by a particular culture for generations. Lacking technological advancement is not same as no appreciation safety and efficacy thus there is a possibility of no adverse effects associated with continuous use of the material. In various instances, harmful effects are reduced through a given method of preparation of the material, by its administration being restricted to qualified personnel-mostly medicine men and women, or by its use being use in special ways, particularly the addition the materials which may decrease the toxicity by countering undesired pharmacological effects or by changing the bioavailability of the material. For example the addition of coca leaves in the traditional method of chewing them. The high favors the less water soluble form of cocaine, so affecting its release into the saliva and absorption to bloodstream, thus reducing the addictive potential
2. Economic and sociopolitical considerations
Although it is not related to the drug discovery process by the industrially developed nations, scientific validation of local drugs from a developing nation may propagate its use and introduction into therapy in its original habitat. Or its growth and adoption as therapy in areas with similar growing conditions. Cultivation and production of extracts of such plants might be a substitute for more drugs and medicines, especial in nations with overstretched healthcare resources
A good example of this is plantas do Nordeste, a collaboration between the Royal Botanic Gardens Kew and a consortium of scientists and agriculturists in the north eastern, Brazil. The project has evaluated some of the local medicinal plants and promoted the cultivation of them across the region as an aspect of healthcare, together with training of personnel in their use. The possible validation of their traditional remedies by the scientific ethnopharmacological approach is also valuable in helping different ethnic groups retain their sense of identity and value, especially when threatened by globalization and cultural imperialism by more political or commercially powerful groups

Some modern examples of Drug Discovery based on the Ethnopharmacotogical Approach:

a) Huperazine A. This is a tea from Huperzia serrata, a club moss, was a traditional drink for elderly people in China. It is an alkaloid with cholinesterase inhibitor properties and has beneficial effects on memory in patients. Since memory appears to be impaired in patients with low levels of acetylcholine in the brain, inhibition of cholinesterase enzyme which degrades acetylcholine will have the net effect of raising acetylcholine levels and hence improving memory. It’s used in treatment of Alzheimer’s disease and senile dementia.
b) Artemesinin. Is a drug used to treat malarial and fevers. The antimalarial compound is isolated from Artemisia annua, acts against the malarial parasite differently as compared to quinine and other synthetic quinolones.
c) Galanthamine. This is a drug isolated from Galanthus found in the Balkans and used by local people for muscle weakness, and also has cholinesterase inhibitory effects. Daffodil bulbs of Narcissus species is mostly used in the production of galanthamine.

Challenges facing drug discovery using Ethnopharmacological approach.
The process of trying to develop medicinal drugs using Ethnopharmacological approach is faced by various challenges, which majorly is due to the community which is at the core of the study, either it is the source of the information or that the raw materials are obtained from that community. Some of these challenges include;
1) A core challenge in pharmacology is the scientific study of the complex products derived from such traditions. Extracts obtained from plants, fungi or animals pose some unique challenges: they are multi-component mixtures of active, partially active and inactive substances and the activity is often not on a single target. Because of this complexity, extracts often vary and thus the pharmacological effects cannot always be reproduced.
2) Reliability of the information. The information obtained from communities cannot be 100% relied upon. This is due to the fact that the person sharing the knowledge may decide to lie rather than giving a correct information. Various diseases manifest with different symptoms and these traditional people may not know that the herb they are using is treating the underlying condition and not the symptom. If they are sharing the information, they will say that that herb treats a condition without knowing that it was a symptom of an underlying condition.
3) Loss of species. There is a high rate of extinction of traditional medicinal plants. Climate change, increasing population making demands on land and resources, as well as commercial exploitation of the environment all play a part in this and result in a loss of habitats. It is not unusual to record the presence of an interesting species in one locality only to return a few months later to find that the whole area has been cleared for some commercial activity. Although ethnic groups in all parts of the world are affected, and most have a rich fund of knowledge about the medicinal uses of local organisms, it is probably those small groups in the centers of biodiversity, especially tropical rainforests, who are most vulnerable to irretrievable loss of species. The imminent extinction or increasing rarity of species are often promoted as a loss of potential new drugs for the developed world; it should be remembered that the local inhabitants may lose many of their basic affordable or available plant medicines
4) Loss of knowledge. The current opportunity to exploit ethnopharmacology may not last long. The irretrievable loss of large amounts of this knowledge results due to the following:
i) When those in possession of knowledge about medicinal plants in a community die, they go with the knowledge if they had not shared this knowledge with other members of the community. ii) Extinction of plant species caused by climate change, urban expansion and destruction of habitat iii) Breakdown in traditional societal structures of the transmission of such knowledge. The threat is especially acute in cultures where transmission is oral rather than written and is exacerbated by urban drift, particularly of young people, neglect of local materials.

CONCLUSION
The study of plants used in traditional medicine has received new force with the introduction of a wide variety of bioassay methods and improved methods for fractionation, isolation and characterization of compounds. Some of the isolated compounds have been as used as lead molecules to the synthesis of new drugs. However, some of the effects observed in the communities are due to mixture of compounds contributing to overall effect. All in all, traditional medicines will continue to provide new molecules for drug discovery and therefore remains a vital area in the field of medicine.