Page 84 - phytochemistry II -pharmD general
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It is used as miotic, after the use of mydriatics or as an antidote after
intoxication with atropine or Solanaceous drugs. It is also used in Alzheimer’s
disease for its parasympathomimetic properties.
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. 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:
1- Cytotoxic agents.
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.
Vinca alkaloids belonging to that last group as they interfere with
deoxyribonucleic acid synthesis.
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