Answer: Periwinkle, or Madagascar periwinkle (Catharanthus rosea), is a tropical perennial that was brought to Europe in 1757 as an ornamental plant. It grows well in temperate climates—zones 9–11 in the U.S. The large-lobed, 50-cent coin sized flowers have colors that vary from white to ‘periwinkle’ blue, to deep pinks, to vibrant reds. The flowers are nicely contrasted by the deep green leaves that jut out of supporting stalks that can reach two feet tall.

Introduction

There are some amazing stories of serendipity in medicine—many are widely known (e.g., breadcrumbs in the Petri dish leading to penicillin). This plant is a contender for a top spot, deserving of a retelling.

The Madagascar periwinkle was initially investigated in the 1950s for the treatment of diabetes.¹ When it was administered it did decrease glucosuria, but also increased blood glucose levels. During its investigation into the treatment of diabetes, researchers injected extract of periwinkle into rats; they reliably died of Pseudomonas septicemia in five to seven days. On autopsy, the rats had multiple abscesses in the liver, kidneys, and other organs. In this particular lab, the unexpected findings were notable because this is what the laboratory had been seeing in rats that were undergoing large dose steroid exposures in another study. When the scientists looked closer, they found that periwinkle extracts resulted in a severe decline in white blood cell count, granulocytopenia, and profoundly depressed bone marrow. Further investigation led to the isolation of the compounds vincristine and vinblastine.²

Toxin/Contribution to Medicine

Vincristine and vinblastine differ by only one carbonyl group—in an aldehyde in the former, and in a methyl group in the latter. In 1961, the Food and Drug Administration approved vincristine as a chemotherapeutic agent for the treatment of Hodgkin’s disease. In 1963 vinblastine, was isolated and approved for the treatment of childhood leukemia. This beautiful, yet poisonous, tropical plant, is responsible for saving millions from cancer.³

Other Uses

• In Cuba and in Puerto Rico, an infusion of flowers together with a few drops of ethanol added was used as an eyewash for infants.
• In Latin America, the leaf tea has been used as a gargle for sore throat and laryngitis.
• In India, the fresh juice squeezed from the leaves was used for wasp stings.
• In Vietnam, herbalists use the leaf and stem tea as a treatment for everything from menstrual difficulties to malaria.
• In Asian cultures, South Africa and Caribbean islands, periwinkle tea was useful as a folk cure for diabetes.

Dr. Hack (@oleanderphotography) is chief of the division of medical toxicology and vice chair for research at East Carolina University in Greenville, North Carolina. He enjoys taking photographs of beautiful toxic, medicinal, and benign flowers that he stumbles upon or grows in his garden.