camptotécine

Camptothecin is a naturally occurring alkaloid that was first isolated from the bark and stem of the *Camptotheca acuminata* tree, native to China. It is a pentacyclic quinoline alkaloid with a unique planar structure. Camptothecin exhibits potent anticancer activity through its inhibition of DNA topoisomerase I. This enzyme is crucial for relieving torsional strain in DNA during replication and transcription. By stabilizing the covalent complex formed between topoisomerase I and DNA, camptothecin leads to DNA strand breaks and ultimately cell death.

Due to its poor solubility and significant toxicity, camptothecin itself is not widely used as a therapeutic agent. However, its discovery spurred the development of semi-synthetic derivatives that have proven to be valuable chemotherapeutic drugs. The most successful of these are irinotecan and topotecan, which are used to treat various cancers, including colorectal, ovarian, and small-cell lung cancer. Research continues to explore new camptothecin analogs with improved efficacy and reduced side effects. The mechanism of action involving topoisomerase I inhibition remains a key area of interest in cancer drug development.