After a slow start in life, Karambu Muriithi is today a RISE student in a hurry. She grew up in a poor region of the equatorial Meru district, near the slopes of Mt. Kenya, where she had the misfortune of belonging to the wrong one of Kenya’s two major clans – the one that did not control the presidency. As a result, the government wasted little funding on Meru, which to this day suffers from famine and poverty.
Nonetheless, Karambu did well in school and became interested in the use of medicinal plants, which she observed all around the countryside of her semi-arid but plant-rich home. She was enthusiastic about her studies, succeeded in graduating from college, and became one of the fortunate few to be accepted in the RISE MSc program in natural products. Since her acceptance, in 2009, she has sped through not only her coursework but her thesis program; she proudly informs a visitor that she is the first chemistry student to finish her thesis and earn a full master’s degree in just two years. With confidence and momentum, she now she plans to continue her studies of healing plants at the PhD level.
The plant she has chosen as her primary subject is a sedge that grows to a height of about six feet. It is common around the world, flourishing in damp, marshy, and flooded areas, but it is also abundant in the drier Meru region, as well as neighboring Theraka. Its tubers are well known to healers, who use them for many herbal remedies.
“I got the idea of using this plant from my grandmother,” she said, “who brought me up. She used the extract on us to treat fevers; she would put it right on our faces. Herbalists all around us also used it to treat almost every kind of ailment and disease, including common cold, fever, malaria, flu, wounds, stomach aches. They call it the wonder drug, and they even use it as perfume.” The plant finds uses wherever the sedge grows, including new applications as a sedative, pain reliever, and, in some cultures, an inducer of dreams. The customary preparation technique is to grind or juice the rhizome and mix the extract with a little water.
To begin her research, Karambu collected some of the essential oil used by herbalists and tested it for activity against common diseases in her University of Nairobi laboratory. She tried it against Staphylococcus aureus (“staph” infection), Streptococcus pneumoniae (pneumonia), and Salmonella (a common cause of intestinal disease); the sedge extract was active against all of them.
One of the experiments she performed was exquisitely simple, if a bit daunting. She enlisted the help of a cage full of hungry mosquitoes. First she put a clean hand into the cage for them to feast on. In five minutes, she recorded 39 landings and 30 bites. After an hour, she put the same hand back in and recorded 63 landings and 55 bites. Then she pulled that hand out and washed, shampooed, and wiped it with ethyl alcohol. Once it was completely clean, she dabbed on about five grams of the plant extract and put it back into the cage. For five minutes, no mosquitoes landed. After an hour, she put the treated hand in again for five minutes; only one mosquito landed, but did not bite. “And even that one I think was a mistake,” she said, “because I had pushed it into a corner.” She has experimented with using the extract as an air freshener, a perfume, and a spray for mosquito netting, all successfully.
She has begun some analytical work using column chromatography to find out what the active fractions of the extract are. She has isolated six compounds, but they are impure. Further purification will depend on additional plant collection, which she says is expensive, and on access to some sophisticated instrumentation, including gas chromatography and a mass spectrometer, that will enable her to identify individual chemical compounds. She has made some progress, but the literature informs her that the extract contains some 59 different terpenes, and she wants to determine which of them – or which combination of them – provides the deterrent effect she has observed. This work lies ahead, and she is eager to devote her PhD years to it. After that, she hopes to return to the slopes of Mt. Kenya with a well-understood and far more useful extract of the plant she’s studying for the herbalists to use with greater precision and confidence.