Fecal and urinary excretion of aflatoxin B1 metabolites (AFQ1, AFM1 and AFB‐N7‐guanine) in young Chinese males

Abstract Our study was designed to assess the fecal and urinary excretion of 3 aflatoxin B 1 (AFB 1 ) metabolites, aflatoxins M 1 (AFM 1 ) and Q 1 (AFQ 1 ) and aflatoxin B 1 ‐N 7 ‐guanine (AFB‐N 7 ‐guanine) that are produced by the predominant forms of cytochrome P450 enzymes responsible for the biotransformation of AFB 1 . Fecal and urinary AFM 1 , AFQ 1 and urinary AFB‐N 7 ‐guanine were assessed in 83 young Chinese males selected from a larger population ( n = 300) based on detectable urinary AFM 1 . The concentration of fecal AFQ 1 (median 137 ng/g fresh weight, IQR 9.1 to 450) was approximately 60 times higher than that of AFM 1 (2.3 ng/g, IQR 0.0 to 7.3). In urine, the median AFQ 1 was 10.4 ng/ml (IQR 3.4 to 23.3), and the median AFM 1 and AFB‐N 7 ‐guanine 0.04 ng/ml (IQR 0.01 to 0.33) and 0.38 ng/ml (IQR 0.0 to 2.15), respectively. A subgroup ( n = 14) with hepatitis B virus (HBV) infection had significantly higher fecal concentrations of AFQ 1 ( p = 0.043) and AFM 1 ( p = 0.001) than those who were hepatitis B‐virus antigen (HBsAg) negative, and the respective differences in urinary AFQ 1 and AFM 1 concentrations approached statistical significance ( p = 0.054, p = 0.138). Our study demonstrates that AFQ 1 is excreted in urine and feces at higher levels than AFM 1 , and feces are an important route of excretion of these AFB 1 metabolites. AFQ 1 should be further assessed for its predictive value as a marker for exposure and risk of dietary aflatoxins. © 2005 Wiley‐Liss, Inc.