Page 92 - Phytochemistry 2 (06-PG 605)

Catharanthus (Vinca) alkaloids
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.
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:
1- Cytotoxic agents.
2- Hormonal therapy.
3- Some antibiotics.
4- The antimetabolites.
Antimetabolites are those agents that interfere with metabolic
pathway to substances vital to cell growth, such as nucleic acid.
Vinca alkaloids belonging to that last group as they interfere
with desoxyribonucleic acid synthesis.
The most important oncolytic Vinca alkaloids are (vinblastine,
vincristine, vinleurosine and vinrosidine). They are useful in the
treatment of many types of cancer (Hodgkin’s disease,
lymphosarcoma and acute leukemia).

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