Medical researchers became interested in the plant during World War Two, when Canadian soldiers stationed in the Philippines used the leaves as a substitute for insulin. The discovery in Jamaica of a “periwinkle tea” with anti-diabetic properties led to further Canadian and American research in the 1950s and the development of drug treatments for cancer.
Extracts of the whole plant have yielded more than 70 different alkaloids of medicinal use. Two of them, vincristine and vinblastine, have raised the survival rate in childhood leukaemia from less than 10% to over 90%. Remission of other forms of cancer, such as Hodgkin’s lymphoma, has also been achieved after chemotherapy with the naturally-occurring alkaloids.
Traditional herbalists use extracts of Madagascar periwinkle to treat high blood pressure, diabetes, bacillary dysentery, rheumatic pains, and abnormally heavy and painful menstruation.
Its scientific name is Catharanthus roseus, formerly Vinca rosea. It belongs to the dogbane family, the Apocynaceae, a Greek word that means “away from dogs”. This refers to the use of some species as dog poison. The family also incorporates the milkweeds, which were previously classified as the Asclepiadaceae, named after Asclepius, the Greek god of healing.
Here are two examples of indigenous medicinal plants in the dogbane family, from the Livingstone area.
Poison-rope, Tacazzea apiculata, is a common vine in woodland fringing the Zambezi. It has milky sap, opposite leaves, and velvety fruits in paired, slender follicles. Traditional herbalists make many uses of this plant, including treating “fits”. Pharmacological research has discovered that extracts do control convulsions and epilepsy.
Kombe tail-flower, Strophanthus kombe, can be found overhanging the path by the Victoria Falls in Zambia’s Mosi-oa-Tunya National Park. Its tiny seeds are used to make drugs for heart conditions. They contain compounds that slow down the heart rate, yet increase the force and efficiency of its contractions. During heart surgery, strophanthin can be administered to stop the heart temporarily.
The seeds are dispersed in a mass of fluff from paired, pod-like fruits that split open when dry, but for pharmaceutical production they are harvested while still in the fruit.
It’s not advisable to ingest any material (or to inhale smoke from burning wood or leaves) from the dogbane family, unless administered by a qualified medical practitioner. This caution includes ornamentals such as frangipani (Plumeria species) and oleander (Nerium oleander).
Read more articles from this issue:
Zambezi Traveller (Issue 08, March 2012)
Read more about the region in our destination guide:
More articles in this series:
Rainforest Riches (ZT, Issue 13, June 2013)
Berry banquet (ZT, Issue 12, March 2013)
Marvellous Mangoes (ZT, Issue 11, December 2012)
Underground Forests (ZT, Issue 10, September 2012)
The healing powers of Aloes (ZT, Issue 09, June 2012)
Dogbane Drugs (ZT, Issue 08, March 2012)
Devil’s Claw (ZT, Issue 07, December 2011)
Elephant Toothpicks (ZT, Issue 06, Sept 2011)