Fecal and urinary excretion of aflatoxin B 1 metabolites (AFQ 1, AFM 1 and AFB-N 7-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.