Areas of interest
Traditional medicine in South Africa
Traditional medicine in South Africa is very similar to traditional medicine systems found in the rest of Africa, south of the Sahara, and plays a very important role in South Africa, where approximately 80 % of the black population makes use of its services. In fact, more people are, in one way or another, employed in the traditional medicine sector than in the western health system. Traditional medicine could be viewed as a parallel system to western health care, much as complementary medicine is in Europe and USA.
Most of the drugs used in traditional medicine are prepared from medicinal plants, also called “muthi-plants”. About 400 plant species are regularly traded in muthi-markets, but more than 1000 plants are known to be used. It is estimated that 20 000 tonnes of plant material is traded each year in South Africa. The majority is sold directly to the patient by traditional healers, but it can also be bought from muthi-shops or at open-air muthi-markets. Unfortunately, all of this material is harvested in the wild, which has led to overexploitation and severe threat to many medicinal plants.
Current research in ethnobotany
In the research group the main interest lies with the rich sources of medicinal plants that are found and used in South Africa. Traditional medicine is an integral part of the culture and 80 % of black South Africans go to a traditional healer when sick. In recent years the Government has realized the need to recognize and formalize traditional healing. If traditional medicine is going to play a more formal role in primary health care it is necessary that it becomes more safe and that the remedies used are optimized for efficiency.
In the Research Centre, we establish the “rational usage” of medicinal plants by investigating plants for the pharmacological activities healers claim they have. Very often we do find that a plant extract has pharmacological activity which supports traditional uses. Furthermore, it is sometimes possible to isolate chemical compounds from the plants which are pharmacologically active. In this way we can lend scientific credibility to what healers have known for centuries.
We also try to establish which plant species are most effective in curing various ailments. We mostly concentrate on what can be termed simple diseases that are a problem especially in rural environments. Diseases such as diarhorrea, which accounts for 40 % of deaths in children under five, and bilharzia are chronic in rural areas. By testing extracts of plants that traditional healers use for their ability to kill amoebae or parasites we can establish which plants are the most effective.
Another area of great concern is the destructive harvesting of medicinal plants in the wild. Several plant species are becoming extinct or are highly endangered. Healers have over the last few years started to accept the idea of growing their own plants in their gardens, but this is not enough and we are at present developing indigenous medicinal plants as alternative crops. We think that many of these species are particularly suited for small scale farming, which would provide rural people with an income and at the same time protect the environment.
Pharmacological and phytochemical tests
The COX-1 and COX-2 bioassays are used to investigate inhibitory activity of plant extracts and compounds against the enzymes cyclooxygenase-1 and cyclooxygenase-2. These enzymes are involved in the production of prostaglandins, which are associated with the inflammatory response.
The disc-diffusion assay and microdilution assay are used for screening plant extracts against various bacteria. The bioautographic assay is a valuable method employed in the bioassay-guided fractionation of active extracts.
The free-living nematode Caenorhabditis elegans is used as a test organism in the anthelmintic assays. The mortality assay is a quick test to determine the direct effect of plant extracts or compounds on the mortality of nematodes, whereas the reproductive survivability assay investigates the effect of extracts on the ability of nematodes to reproduce, in addition to the effect on their mortality.
Anti-bilharzia / schistosomiasis assay
An in vitro dilution system is used to test the activity of plant extracts against the human stage of the schistosome parasite.
Various tests are used for investigating phytochemical properties of plant extracts. Some of these include tests for: Tannins, Saponins, Cardiac glycosides, Cyanogenic glycosides and Alkaloids.
Conservation of medicinal plants
Many medicinal plants are under threat due to over-collection and destructive harvesting practices. At present, most of the plant material used in traditional medicine is harvested in the wild by gatherers, who usually collect everything they think can sell without regard to how the plants will survive for the future. More than half of the plant material sold as traditional medicine consists of bulb, rhizomes or bark. When underground parts are harvested, the whole plant is removed, and too often a tree is ring-barked, resulting in the death of that tree. It has become increasingly difficult to collect enough material from the wild, and several species can no longer be found and have to be imported from neighbouring countries (where they are most likely to disappear as well).
If a plant is threatened so there is limited stock material left, or if the seeds are difficult to germinate, or the species cannot be propagated via normal methods, then clonal propagation in tissue culture might be the alternative way of producing a lot of plants. These plants can be replanted in nature to restore the environment or can be used for commercial production of medicinal plants. The need for medicinal plants is not diminishing, rather, it is increasing. It is therefore necessary to find other ways to produce the amount of plant material that is needed. During recent years traditional healers have started to grow medicinal plants in their own gardens. This alleviates the situation in some ways, but it is not enough.