Scientists break botanical boundaries
Bid to conserve and commercialise medicinal plants gains pace, writes Tamar Kahn
NOKWANDA Makunga stands in her airy greenhouse at Stellenbosch University holding a tiny, green succulent shrouded in lacy leaf skeletons. Usually such skeletons only emerge long after dead leaves have fallen from the plant and their tissues rotted away, but not in the case of this hardy Karoo resident called Sceletium tortosum.
“We think these skeleton leaves protect it from the sun like a linen scarf,” says Dr Makunga, gently placing the plant back in its place.
It is just one of the local flora under investigation by Dr Makunga and her team in the botany department, where scientists are trying to find ways to conserve and commercialise local medicinal plants. “Southern Africa has a golden wealth of medicinal plants, between 4,000 and 5,000. But most are simply harvested in the wild without any value-adding processes. We’re losing out on developing new products,” she says.
Sceletium has traditionally been used by the San as a mood enhancer, pain reliever and sleeping aid. It contains a variety of alkaloids that affect the nervous system.
One of these is mesembrine, which scientists think acts as a serotonin reuptake inhibitor in much the same way as antidepressants such as Prozac. Dr Makunga and her team are trying to determine the optimal growing conditions for Sceletium to synthesise mesembrine.
“This is where technology and traditional knowledge meet. We are generating the knowledge we hope will fuel the bio-economy,” she says.
Instead of cultivating fullgrown plants, the scientists are growing blobs of Sceletium cells in glass flasks. Their aim is twofold: to identify the “elite chemo types” that produce the most alkaloids, and to optimise the growth medium so they can mass-produce plant tissue cultures that can go into agricultural production.
“Sceletium grows in the wild in a very arid environment, and on a small scale. We think there is potential for overharvesting,” she says.
Overharvesting poses a threat to many other indigenous medicinal plants, including wild ginger and Tulbaghia, or wild garlic, she says. Tulbaghia is a bulb that is highly prized for treating infections, fevers and asthma.
“When you speak to the ‘bush’ doctors, they say it is getting harder to find,” says Dr Makunga. She is working with Rastafari bush doctors in the Western Cape, who are trying to reintroduce KhoiSan healing traditions to inhabitants of townships.
“They feel they are bringing back a lost culture to marginalised communities.”
These “bossiedokters” as they are called in Afrikaans are the biggest traders in traditional medicinal plants indigenous to the Western Cape, but their trade in medicinal plants is a small fraction of what is bought and sold in SA. A study published last year by Dr Lisa Philander estimated between 35,000 and 70,000 tonnes of medicinal plants changed hands each year, only 1% of which she attributed to the Rastafari traders.
Dr Makunga is collaborating with Rastafari bush doctors on a plant that has potential for a cancer treatment. She declines to name the plant, saying only that it is something “people hike past”.
“It could be used as an adjunct cancer treatment along with chemotherapy or radiation treatment,” she says, but cautions that research is still at a very early stage. Studies in mice yielded promising results and a patent application is pending, but much more work still lies ahead to determine if it is safe and effective in humans.
“It would have to go into clinical trials,” she says. Scientists would also need to set up a benefit-sharing agreement with the holders of the indigenous knowledge.
Dr Makunga is not just interested in indigenous plants. She is also looking into the agricultural potential of natives to other parts of the world such as Stevia rebaudiana, an alternative to sugar that has taken the food industry by storm because it does not appear to affect bloodglucose levels.
Stevia is a relative of the crysanthemum and is indigenous to Brazil and Paraguay, where it has traditionally been used to sweeten mate tea.
It is now grown commercially in many other parts of the world, including East Africa, and its extract is increasingly finding a home as a sweetener in processed food and drink.
Dr Makunga is researching its nutrient needs and trying to identify the best soil types for cultivating the faintly liquorice-tasting leaf.