Page 86 - phytochemistry general program

During the last 20 years, about 60 alkaloids were isolated from some Vinca
or Catharanthus species. All of these alkaloids are chemically related and are

referred to collectively as Vinca alkaloids.

The great value of this group of recently discovered alkaloids arises from
their antitumor activity. As many of these alkaloids have been tested for their
oncolytic activity and some were found to be effective in controlling and

suppressing the growth of malignant cells.
Some of these alkaloids (vinblastine & vincristine) are now applied for the
treatment of certain types of cancer, and they have been shown to be effective in

producing of partial or even complete regression of the disease.

It is important to note that, of the many thousands of organic compounds that
have been studied in tumor-bearing animals, only few have shown to influence
human cancer. The classification of these cancer inhibitor is based on their mode

of action, the classes are:

Cytotoxic agents. .1
.2
Hormonal therapy. .3
. Some antibiotics .4

The antimetabolites: They are those agents that interfere with metabolic

pathway to substances vital to cell growth, such as nucleic acid.

alkaloids belonging to that last group as they interfere with Vinca
.deoxyribonucleic acid synthesis

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.

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