[{"from": "human", "value": "Please give me some details about this molecule. [C][C][C@@][Branch2][Branch1][C][C][=C][Branch1][#Branch1][C][O][C][Ring1][=Branch1][=O][C][=Branch1][C][=O][N][C][C][=C][C][=C][Branch1][S][C][=C][C][=Branch1][#Branch2][=C][Ring1][=Branch1][C][N][Branch1][C][C][C][O][N][=C][Ring1][#C][C][Ring2][Ring1][C][=C][Ring2][Ring1][O][O]"}, {"from": "gpt", "value": "The molecule is a semisynthetic derivative of camptothecin, a cytotoxic, quinoline-based alkaloid extracted from the Asian tree Camptotheca acuminata. Topotecan inhibits topoisomerase I activity by stabilizing the topoisomerase I-DNA covalent complexes during S phase of cell cycle, thereby inhibiting religation of topoisomerase I-mediated single-strand DNA breaks and producing potentially lethal double-strand DNA breaks when encountered by the DNA replication machinery."}]