IDENTIFICATION OF THE PRINCIPAL BILIARY METABOLITE OF 4'-(9-ACRIDINYLAMINO)METHANESULFON-META-ANISIDIDE IN RATS

Abstract

M-AMSA [4''-(9-acridinylamino)methanesulfon-m-anisidine] labeled in either the acridine or anilino portion was used to investigate the disposition of this antitumor agent in rats. The principal biliary metabolite, which accounts for approximately 80% of the total biliary radioactivity for 90 min after administration and > 50% of the administered dose by 180 min after administration, had both the acridine and the anilino portions intact. Isolation and purification of the principal metabolite was achieved by preparative TLC on silica gel and column chromatography on Amberlite XAD-2 resin. A NMR spectrum of the DCl salt in D2O showed that the metabolite is the m-AMSA-glutathione conjugate in which the thioether linkage occurs at the 5''-position of the anilino ring. Synthesis of the metabolite was achieved by oxidizing m-AMSA with active MnO2 to N1''-methanesulfonyl-N4''-(9-acridinyl)-3''-methoxy-2'',5''-cyclohexadiene-1'',4''-di-imine (m-AQDI) followed by reaction of m-AQDI with glutathione. The 1H-NMR spectrum of the synthetic product proved identical with that of the isolated metabolite. The demonstration that the principal biliary metabolite of m-AMSA involves glutathione bound to the 9-anilino ring suggests that m-AMSA may be bioactivated in vivo to the quinoidal dimine, m-AQDI.