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Also known as Madagascar periwinkle, rosy periwinkle is a perennial sub shrub with many branches that grows up to two and a half feet tall. Leaves are oval and have a glossy surface. The five-lobed flowers are usually white or light pink. The long seedpods are cylindrical and have a downy texture. The whole plant is used. The plant that serves so many people in so many important ways is both demure and beautiful. Although it is native to the Indian Ocean island of Madagascar, the Madagascar periwinkle is extensively cultivated, and it has become naturalized in many warm regions of the world, including the southern United States. There are a number of varieties available commercially, with colors ranging from hot pink to mauve and white. In seed catalogs, the Madagascar periwinkle and its varieties are often grouped with true periwinkles (Vinca).

Few plants have generated as much recent interest among the scientific and medical communities as the Madagascar periwinkle, C. roseus (also known by its older name Vinca rosea). The interest began in the mid-1950s, when researchers, hearing of a "periwinkle tea" that was drunk in Jamaica, began to study the plant for its reported antidiabetic properties. They found much more than they had hoped for; the plant, they found, contains two anticancer alkaloids- vincristine and vinblastine- that inhibit the growth of tumors. Vincristine has proved most effective in treating childhood leukemia; vinblastine in treating testicular cancer and Hodgkin's disease (cancer of the lymphatic system). Like many drugs used in chemotherapy, both alkaloids produce such side-effects as nausea and hair loss.

Along with the lesser periwinkle, rauvolfia, and other members of the dogbane family, the Madagascar periwinkle is endowed with other medicinal assets, too. Madagascar periwinkle contains over 70 different indole alkaloids, including vinblastine, vincristine, alstonine, ajmalicine, leurocristine, and reserpine. Some of these decrease blood sugar levels; others reduce blood pressure.

Long before modern researchers learned of the plant's valuable and varied properties, folk healers in faraway places were using the Madagascar periwinkle for a host of medicinal purposes. In India, they treated wasp stings with the juice from the leaves. In Hawaii, they prescribed an extract of the boiled plant to arrest bleeding. In Central America and parts of South America, they made a gargle to ease sore throats and chest ailments. In Cuba, Puerto Rico, Jamaica, and other islands, an extract of the flowers was commonly administered as a soothing eyewash. Periwinkle is used in folk medicine in the Philippines as a remedy for diabetes. Most of these practices are still followed.

Madagascar periwinkle's traditional use as a treatment for diabetes has led to extensive investigation into its properties. Vincristine and vinblastine are powerful anticancer agents, and are two of the most important medicinal compounds found in plants in the last 40 years. Vincristine is a standard treatment for Hodgkin's disease, and vinblastine for childhood leukemia. Although extracts from Madagascar periwinkle have been shown to lower blood sugar levels, simple preparations of the whole plant may not be effective.

Periwinkle was called "sorcerers violet" by the French, in reference to its use in charms and love potions. Europeans also believed that periwinkle had the power to exorcise evil spirits. Medieval Europeans used rosy periwinkle frequently in garlands to protect the bearer. The Italians placed garlands of the plant on the graves of infants, calling it the flower of death. During the Enlightenment in Europe, the French considered periwinkle an emblem of friendship.

Periwinkle has been used for health problems ranging from memory loss to toothache and from circulatory disorders to intestinal inflammation. Although its effectiveness in treating all these ailments has not been proved, periwinkle has been shown to lower blood sugar and to act as a diuretic. In testing the plant as a drug source for diabetes in the 1950s, an extract was found that proved successful in treating juvenile leukemia, Hodgkin's disease, and other cancers that were previously considered largely incurable. The main alkaloids, vinblastine and vincristine, appear to bind to proteins in some microtubules, facilitating cancer-cell death.