Abstract
Four cytotoxic alkaloids (vinblastine, vincristine, vinrosidine and vinleurosine) have been isolated from Vinca rosea. They are active only on proliferating cells. Their cytocidal effect is limited to distinct phases of the cell cycle. Morphological substrate of the alkaloid action is a mitotic arrest in metaphase with the appearance of typical C–mitoses. A deaggregation of the spindle apparatus by the Vinca alkaloids and physico–chemical interactions with structure proteins of the microtubules could be demonstrated. An inhibition of DNA synthesis is a secondary effect due to the metaphase block of the cells by preventing them from continuing their cell cycle.
