title: Relationship of the reductive metabolism of indicine N-oxide to its antitumor activity.
abstract: Several pyrrolizidine alkaloids have been demonstrated to have antitumor activity in experimental tumor systems. In general the free base form of the alkaloid exhibits greater biological activity than the  corresponding N-oxide and the N-oxide must be metabolized to the base for the subsequent formation of alkylating intermediates. Indicine N-oxide is an exception in that it is a more active antitumor agent than its free base indicine. Studies of the antitumor activity and metabolism of indicine N-oxide, and the closely related compound, heliotrine N-oxide, given orally and intraperitoneally to mice bearing P-388 leukemia, suggest that conversion of indicine N-oxide to indicine is not essential for its antitumor activity.
mesh_terms: D000693:Anaerobiosis; D000818:Animals; D000972:Antineoplastic Agents, Phytogenic / Q000627:therapeutic use; D003497:Cyclic N-Oxides / Q000378:metabolism / Q000494:pharmacology / Q000627:therapeutic use; D066298:In Vitro Techniques; D007942:Leukemia, Experimental / Q000188:drug therapy / Q000378:metabolism; D008297:Male; D051379:Mice; D008862:Microsomes, Liver / Q000378:metabolism; D010084:Oxidation-Reduction; D011763:Pyrrolizidine Alkaloids / Q000378:metabolism* / Q000494:pharmacology / Q000627:therapeutic use
chemical_list: D000972:Antineoplastic Agents, Phytogenic; D003497:Cyclic N-Oxides; D011763:Pyrrolizidine Alkaloids; C020350:heliotrine N-oxide