Page 85 - phytochemistry II -pharmD general

Occurrence

Catharanthus or vinca is the dried whole plant of Catharanthus roseus G.
Don (or Vinca rosea L), family Apocynaceae.

The alkaloids occur in all parts of the plant. The valuable antitumor alkaloids
constitute only a small percentage of the total alkaloidal content. So, they are
obtained in a very small yield from the plant. Vinblastine and vincristine amounts
to about 0.003 to 0.005% of the powdered whole plants.

Cell culture and organ cultures have been attempted, with considerable
success in producing the oncolytic dimeric alkaloid, but in a yield that was still less
than that from the crud drug .

It contains about 90 alkaloids, the most important are vinblastine and
vincristine. These are present in very minute amounts in the plant but are known
to have antineoplastic (cytotoxic) activity.

Chemically, vinca alkaloids are indole or indoline derivatives. They are
classified into two main groups:

1) Monomeric alkaloids: catharanthine and vindoline.

They are sub divided into:

a) Indole monomeric alkaloids (catharanthine-type): e.g. catharanthine

b) Indoline monomers (vindoline-type): e.g. vindoline

1. Monomeric Vinca Alkaloids

N

N

N *
H3COOC
H3CO N OCOCH3
HO COOCH3

* CH3

Catharanthine Vindoline

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