Co-chromatographic identification of PRA metabolites. Elution profiles of chemically synthesized references are shown in traces (A): 8-OH-PRA, F-6; (B): the 7-amino metabolite of PRA, F-9; and (C): the 3-hydroxy-congener of PRA, F-1. Trace (E) represents the elution profile of concentrated supernatants. In trace (D), concentrated supernatant had been spiked by adding compounds A, B and C to approximately double their concentrations. Note the reversed order of F-6 and F-9 (as compared to Figure 1), due to the shallower gradient applied; retention times are summarized in Table 1. Absorbance was recorded at 270 nm.