Plant products

Antineoplastic Agents - SYNTHESIS AND DRUG PROFILE

Plant products

a. Vinca alkaloids

Vincristine R = CHO

Vinblastine R = CH₃

Mode of action: It binds to microtubular protein tubulin, prevents polymerization and assembly of microtubules, and causes mitotic spindle destruction. The chromosomes fail to move apart during mitosis and lead to metaphase arrest.

Properties and uses: Vinca alkaloids are isolated from Catharanthus roseus. They have complex structures composed of a dimeric indole-containing moiety named catharanthine and an indoline-containing moiety named vindoline. Four closely related compounds have antitumour activity, that is, vincristine, vinblastine, vinrosidine, and vinleurosine. Semisynthetic derivative vinorelbine is also used as an antitumour agent.

Vinorelbine

Properties and uses: They are used for the treatment of acute leukaemia, Hodgkin’s disease, testicular cell tumour, lymphocytic lymphoma, histicytic lymphoma, and carcinoma of the breast.

b. Camptothecin derivatives

Properties and uses: Camptothecin is a pentacyclic alkaloid originally isolated from Camptotheca acuminata. These drugs are used for the treatment of colorectal and ovarian cancers.

c. Epipodophyllotoxins

Mode of action: It arrests cells in G₂ phase and causes DNA breaks by affecting the DNA topoisomerase function and the resealing of DNA strand is prevented.

Properties and uses: Etoposide and teniposide are semi-synthetic derivatives of podophyllotoxin. It is obtained as extracts of May apple plant. It is effective in the treatment of lung cancer, testicular cancer, and Hodgkin’s disease.

d. Taxol derivatives

Mode of action: This stabilizes the polymerization of tubulin and the depolymerization is prevented.

Properties and uses: The taxol derivative, paclitaxel, is isolated from the Western row tree, Taxus brevifolia. It is the first member of the taxane family used in cancer therapy. It is used for metastatic ovarian and breast cancer, lung, mouth, oesophageal, and bladder carcinomas.