Identification of metabolite M15′. Duplicate incubations were conducted in 1× PBS (pH 7.4) containing ATV (50 μM), HLM (0.5 g of protein/l), and INH (5.0 mM), with or without NADPH (1.0 mM). The metabolites were analyzed using UPLC-TOFMS. A, chromatograms of M15 and M15′-hydrazone. B, MS/MS of M15. C, MS/MS of M15′-hydrazone.