I grew up in Woodbrook, surrounded by pots of Old Maid. They were my mother’s favourite flower and the dozen steps leading up to our house had a pot of Old Maid at each end. They served not only as decoration but as a sort of barrier preventing small children from falling. Despite this, I tumbled over and landed on my gluteus maximus. Not having much of that, I damaged my coccyx and hobbled around for days, pushing my posterior out to limit the pain.
The front garden was full of Old Maid. It seemed to grow effortlessly without having to be planted or weeded. From the upstairs balcony, the garden appeared covered with a carpet of pinkish-violet coloured flowers, each composed of five petals, often single but when fully blossomed, each stalk bearing two or even three flowers.
We’ve had Old Maid in our present garden for years. Since my mother’s death two years ago, it seems to have decided to propagate everywhere. Old Maid looks weak but it’s called Old Maid because it gets little attention, yet is delicate and pretty, like my mother. In the early morning and late evening, the plants are surrounded by bees and butterflies. That adds more colour to the garden.
Its real name is the Madagascar Periwinkle or Catharanthus roseus and as simple and common as it appears, it has saved the lives of hundreds of thousands of children with cancer of the blood or Acute Lymphoblastic Leukaemia (ALL). Amazingly, it contains two compounds, vincristine and vinblastine, which form the basis of treatment for all children with ALL, as well as other types of cancers.
The discovery of these chemicals has links to the Caribbean and its discovery is a fascinating example of medical serendipity. A tea from the leaves has historically been used in many cultures, including Jamaica, as treatment for diabetes. As this Jamaican tea was being investigated in the 1950s, it was found that it did not lower the blood sugar levels in rats. Rather, it killed them. They died of infection. Someone then noticed that the rats who died had low white blood cell counts, which had caused the infections.
Out of over 200 chemicals isolated in the tea, vincristine and vinblastine were found to be the agents that decreased those white blood cells. ALL is characterised by the abnormal proliferation of white blood cells. Since then, vincristine has been used to destroy cancerous white blood cells and is an essential part of the chemotherapy for ALL. It was a huge breakthrough.
Vincristine is primarily found in the leaves of the plant but all of its parts contain the chemical and it is poisonous to humans and animals. The amounts are tiny. Two thousand kg of dried leaves are needed to obtain 1g of vincristine, and vast plantations of periwinkle can be found in India, the Philippines and South Africa.
As usual, the native farmers and original users of the periwinkle in Madagascar have been isolated from the profits of cultivating the plant.
There are about 400,000 plants in the world and the question comes up: why do plants produce these toxic compounds? Plants can’t run away from their predators, caterpillars and moulds, so they depend on chemical defences which they developed in their evolution. All of these anti-cancer drugs kill not only cancer cells but plant predators.
The periwinkle is not the only plant that makes anti-cancer drugs: Other examples include “Taxol”, from the pacific yew tree Taxus brevifolia, which grows in the Pacific forests of North America and is used to treat breast and lung cancer. “Etoposide” for testicular cancer and “teniposide” for brain cancer are derivatives of podophyllotoxin, found in the American Mandrake plant Podophyllum peltatum and used to treat genital warts.
Anti-cancer compounds are not the only ones found in plants. “Willow” bark is a natural painkiller and its chemical, salicin, was further developed as aspirin. The berries of “Deadly Nightshade” (Atropa Belladonna) were traditionally used to dilate the pupils of women in an attempt to make them a belladonna (beautiful woman) and now provide us with the drug atropine. “Foxglove” contains digoxin, the cardiac stimulant. And we all know about the “poppy” from which we derive morphine but also heroin.
These drugs are based on discoveries made decades and even centuries ago, but the search for more therapeutic compounds from plants goes on.
It’s fascinating to speculate that something found in one of our common “teas” may mean another breakthrough in the treatment of another disease, which leads us back to that simple, little flowering plant in the garden.
