Madagascar periwinkle  (Catharanthus roseus)

This species has not been assessed by the IUCN.

One of the major medical breakthroughs of the last century utilises compounds derived from a popular ornamental plant found in gardens and homes across the world, the Madagascar periwinkle (2) (3). This tender, perennial plant grows as a herb or a subshrub, sprawling along the ground or standing erect up to a metre in height (2). The attractive white or pink flowers comprise five petals spreading from a long, tubular throat (2), while the leathery, dark green leaves are arranged in opposite pairs (2) (4). Each fruit is formed of two narrow, cylindrical follicles which house numerous grooved seeds (2). Like many other plants in the Apocynaceae, the sap is a milky latex (2) (5).

The Madagascar periwinkle is indigenous to Madagascar, but is cultivated and naturalised throughout the tropics and parts of the subtropics (2).

Found on sand and limestone soils in woodland, forest, grassland, and disturbed areas (2).

Although the Madagascar periwinkle has a flower adapted to pollination by a long-tongued insect, such as a moth or butterfly, this species, unlike most in the Apocynaceae family, is also able to self pollinate. Self compatibility and a relatively high tolerance of disturbance have enabled this species to spread from cultivation and naturalise in many parts of the world. As a consequence, this species is sometimes considered to be an invasive weed, although it does not normally proliferate sufficiently to eliminate native vegetation (3). The seeds of the Madagascar periwinkle are reportedly distributed by ants (2).

Traditionally, the Madagascar periwinkle has been used to treat a variety of ailments in Madagascar and in other parts of the world where the plant has naturalised. Whilst researching the anti-diabetic properties of the plant in the 1950s, scientists discovered the presence of several highly toxic alkaloids in its tissues. These alkaloids are now used in the treatment of a number of different types of cancer, with one derived compound (vincristine) credited with raising the survival rate in childhood leukaemia from less than 10 percent in 1960 to over 90 percent today (2) (3).

While Madagascar’s forests have been heavily impacted by human activity, the Madagascar periwinkle’s ability to thrive in disturbed areas has enabled it to survive on its island home (3). Furthermore, it is widely established in the wild throughout tropical regions of the world, is commonly cultivated in gardens and homes, and is grown commercially in the pharmaceutical industry (2) (3).

Given the modern ubiquity of naturalised and cultivated populations of Madagascar periwinkle, direct conservation measures are a low priority for this species (3). Nonetheless, the discovery of powerful medicinal plants, such as the Madagascar periwinkle, is a potent reminder of the need to conserve and study the increasingly threatened plants and habitats of the world (6).

For further information on the Madagascar periwinkle see:

• The Encyclopedia of Life:
  www.eol.org/pages/581125