|
|
|
 |
I
N
D
I
A
N
M
E
D
I
C
I
N
A
L
P
L
A
N
T
S
Catharanthus roseus
Catharantus roseus (L.) G. Don, (= Vinca rosea L., Lochnera rosea Reichb.), Apocynaceae, Madagascaran periwinkle, is a native of Madagascar, now naturalised in many tropical countries, particularly India. However, some consider that the species is a native to India.
The original, now largely discontinued, medicinal use of this species in its native country, was as an antidiabetic, on account of the indole alkaloids catharanthine, leurosine, lochnerine, tetra-hydroalstonine, vindoline and vindolinine, as well as the anthocyanin in the leaves.
The species produces several alkaloids generally known as vinca alkaloids. More important among them are the indole alkaloids, vincristine and vinblastine, which are oncolytic, and reserpine and ajmalicine, which are hypotensive and tranquillising.
On discovering that the alkaloid vincristine reduces white blood cell count drastically, it was developed as an anti-leukaemic agent. Vincristine is now possibly the only effective drug against leukaemia, although with considerable side effects, and is one the most expensive plant products (US$ 24,000/g).
Vinblastine, effective against Hodgkin’s disease, is present in periwinkle in quantity more than 1, 000 times of vincristine. Since vinblastine is far cheaper than vincristine (US$ 6,800/g), it is converted into vincristine by biotransformation.
Totally synthetic vincristine is far less efficient than the natural product, and hence the importance of the species is unchallenged.
Vincristine and vinblastine have an antifertility effect in males.
a-acylindolic acid (perivine) is effective against A2 influenza virus.
As shown in the photograph Catharanthus roseus1, two varieties of periwinkle occur in the wild, often growing together (sympatric). The most common variety has pink flowers and reddish stems, while the other has white flowers and green stems. This is an example of infraspecific genetic variation, which is not associated with the synthesis of the alkaloids. There are also several other varieties grown in gardens.