Function: Camptothecin showed remarkable anticancer activity in preliminary clinical trials by inhibiting the DNA enzyme topoisomerase I (topo I). (S)-(+)-Camptothecin binds irreversibly to the DNA-topoisomerase I complex, inhibiting the reassociation of DNA after cleavage by topoisomerase I and traps the enzyme in a covalent linkage with DNA. The enzyme complex is ubiquinated and destroyed by the 26S proteasome, thus depleting cellular topoisomerase I. Blocks the cell cycle in S-phase at low does and induces apoptosis in a large number of normal and tumor cell lines by cell cycle-dependent and cell cycle-independent processes. Application: 1. Camptothecin is the natural starting material of Irinotecan HCl. 2. Camptothecin is the natural starting compound of 10-Hydroxycamptothecin. 3. Camptothecin is the natural starting ingredient of 7-Ethyl-10-Hydroxycamptothecin(SN-38). 4. Camptothecin is the natural starting ingredient of Topotecan HCl 5. This compound camptothecin is a featured product for Apoptosis research.