am·i·nop·ter·in  (ām'ə-nŏp'tər-ĭn)  n. A folic acid antagonist, C19H20N8O5, used as an antineoplastic agent. It has been mainly replaced by methotrexate. [amino- + pterin, a chemical compound derived from pteridine, a compound first identified in butterflies' wings (from Greek pteron, wing; see pet- in Indo-European roots).] |