School of Life Sciences

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

• Anti-inflammatory assays
  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.
  
  
• Antibacterial assays
  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.
  
  
• Anthelmintic assays
  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.
  
  
• Phytochemical screening
  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.

There are two main areas of focus within our laboratory: i) stress physiology; and ii) genetic modification of useful crop resources:

Unlike most animals, plants cannot get up and move to a better place when conditions do not favour their growth or survival. They have thus evolved a variety of fascinating mechanisms to help them survive. In South Africa, we experience a wide range of environmental conditions, large areas are simply unsuitable, at present, for cultivation of crops. By understanding how plants adapt to harsh conditions, such as extremes of temperature, high concentrations of salts in the soil and drought, it may one day be possible to modify crop species to grow in areas which are presently considered marginal for agriculture.

Molecular techniques are also being used to introduce useful traits into some of the more widely-used species in the forestry industry. World demand for forestry products are on the increase, whilst natural resources are declining. Biotechnology offers solutions to problems encountered in mass propagation, tree improvement, selection of superior genotypes and germplasm conservation. In addition, our laboratory is involved in trying to increase the production of pharmacologically-active chemicals in plants, where these may only be extracted from plants and cannot at present be chemically synthesized in vitro. This means that medicines containing these compounds are often exceedingly expensive. Should it be possible to modify these plants to overproduce these pharmacologically active compounds, the cost of such medicines could potentially be reduced, making them available to a larger proportion of society.

Plant Physiology is the study of processes within plants. Research interests related to plant growth and development within the Research Centre are varied and cover two main themes: (1) Tissue culture and micropropagation; and (2) Plant growth regulators, including herbicides. Research is both pure and applied with an emphasis on biotechnology.

Tissue culture and micropropagation
South Africa has a rich and diverse flora with over 30 000 species of flowering plants – almost 10% of the world’s higher plants. Traditionally, plants have been used by indigenous people for herbal medicines. Flowering bulbs and other fynbos species are prized in the cut-flower industry. Rapid urbanization and overexploitation of wild species by the horticultural trade and by traditional medical practitioners has led to a decline in many species.

Tissue culture is a means of preserving species that are rare and threatened and providing an alternative source of plants for commercial, horticultural and traditional medicinal trade. Tissue culture is the “aseptic culture of plant protoplasts, cells, tissues or organs on a culture medium which is as defined as possible; the cultures are maintained under controlled environmental condition”. Our the three main areas of expertise are: i) Tissue culture of ornamentals and medicinal plants; ii) Tissue culture in forestry; and iii) Tissue culture and secondary metabolite production.

• Tissue culture of ornamentals and medicinal plants
  The main difficulty in growing indigenous plants in large quantities is to obtain sufficient plant material. Seeds may germinate erratically and bulbs usually propagate by offsets. This makes production too slow to warrant their introduction as new commercial crops. In vitro methods are used to speed up propagation. The success of the system lies in the development of strict protocols for each species. This involves improving decontamination procedures and determining the effects of various cultural factors on plant growth, both in vitro and ex vitro to establish optimum growing conditions.
  
  
• Tissue culture in forestry
  Pinus patula is the most important commercially grown softwood species in South Africa. Clonal propagation of superior clones is gaining favour in the forestry industry. Conventional methods of clonal propagation involve the rooting of cuttings. However, the taking of cuttings from trees older than four years is problematic due to maturation effects. Somatic embryogenesis offers a means of mass producing superior clones. Somatic embryos can be encapsulated to produce large quantities of artificial seeds. Embryogenic tissue can be cryopreserved to maintain it in the juvenile state, thereby overcoming maturation constraints and can also be used in genetic engineering to improve disease resistance and tolerance to environmental stresses. Somatic embryos have been successfully induced in Pinus patula and these have been maintained in vitro within the Research Centre. Embryogenic tissue has also been cryopreserved and field trials of the somatic seedlings are being conducted.
  
  Eucalyptus and wattle are also important in the wood-pulp industry in South Africa and ways of improving their production are being investigated. Areas of interest include improving vigor of cuttings and ways to store pollen to improve its viability.
  
  
• Tissue culture and secondary metabolite production
  Secondary metabolites are compounds produced in plants that are not necessary for the plants basic functions although some act as chemical defenses against microbes and animals. Secondary metabolites are used in the pharmaceutical industry as flavourants and dyes, and in perfumery. As conventional growing of medicinal plants is relatively expensive, production of medicinal and/or other compounds can be elicited in vitro. Hypoxoside produced by Hypoxis species, is used as an anticancer drug. This has been successfully produced in callus cultures within the Research Centre. Red pigmented anthocyanins, used as a food colourant, have been produced from the callus of Oxalis species in the Research Centre.

Plant growth hormones and growth regulation

• Hormone Physiology
  Hormones are vital in controlling the growth and development in plants. Plant hormones are classified into five major groups, namely cytokinins, auxins, gibberellins, ethylene and abscisic acid. Bioassays are an integral part of hormone research. A number of bioassays are routinely used in the Research Centre e.g. the soybean bioassay and the mung bean bioassay. Radiochemistry facilities are also available in the Research Centre, allowing for the elucidation of biochemical pathways within plants. Using chromatographic techniques such as paper chromatography, TLC, sephadex and HPLC, the occurrence and metabolism of hormones including cytokinins, auxins and abscisic acid have been investigated in a range of lower and higher plants. Cytokinins and auxins have also been identified in some commercial seaweed products used in agriculture.
  
  
• Growth regulation and herbicides
  Plant development is influenced by environmental signals which are transduced into physiological responses. These processes involve plant hormones and regulators. The nature of the plant’s reaction depends on endogenous levels and the interaction between the different classes of regulators. Understanding the effects of growth regulators allows for the improvement of plants, including commercial crops, by influencing various physiological processes such as flowering and fruit set.

Many weed biotypes are resistant to herbicides. Identification and characterization of herbicide resistant weed biotypes is necessary. The use of a newly developed plant growth regulator which alters plant growth, development and production is currently underway by members of the Research Centre. Addition of Plant Growth Regulators to herbicides to enhance efficiency of herbicides is also under investigation.

• Seed biology
  Smoke from burning vegetation contains a chemical messenger which triggers seeds of many species to germinate. This interesting mechanism ensures that seeds germinate at an optimal time when there is sufficient light and space immediately after a veld fire. Aqueous extracts of smoke can be used for commercial purposes. They are currently used in land restoration and have the potential to play an important role in the conservation of “difficult-to-germinate” plant species.
  
  Poor seedling germination and vigor reduce the market value of many commercial seeds. Numerous reasons for poor seed quality are being investigated by members of the Research Centre.