AUTHOR=Guo Wenbo , Fan Zhichen , Fan Kai , Meng Jiajia , Nie Dongxia , Tangni Emmanuel K. , Li Zenghe , Zhao Zhihui , Han Zheng TITLE=In Vivo Kinetics and Biotransformation of Aflatoxin B1 in Dairy Cows Based on the Establishment of a Reliable UHPLC-MS/MS Method JOURNAL=Frontiers in Chemistry VOLUME=9 YEAR=2021 URL=https://www.frontiersin.org/journals/chemistry/articles/10.3389/fchem.2021.809480 DOI=10.3389/fchem.2021.809480 ISSN=2296-2646 ABSTRACT=

The in vivo kinetics of aflatoxin B₁ (AFB₁) and its carry-over as aflatoxin M₁ (AFM₁) in milk as well as the toxin loads in the tissue of dairy cows were assessed through a repetitive feeding trial of an AFB₁-contaminated diet of 4 μg kg⁻¹ body weight (b.w.) for 13 days. This was followed by a clearance period that ended with a single dose trial of an AFB₁-contaminated diet of 40 μg kg⁻¹ b.w. An ultra-high performance liquid chromatography tandem mass spectrometry method was developed and successfully validated by the determination of linearity (R² ≥ 0.990), sensitivity (lower limit of quantification, 0.1–0.2 ng ml⁻¹), recovery (79.5–111.2%), and precision relative standard deviation (RSD) ≤14.7%) in plasma, milk, and various tissues. The repetitive ingestion of AFB₁ indicated that the biotransformation of AFB₁ to AFM₁ occurred within 48 h, and the clearance period of AFM₁ in milk was not more than 2 days. The carry-over rate of AFM₁ in milk during the continuous ingestion experiment was in the range of 1.15–2.30% at a steady state. The in vivo kinetic results indicated that AFB₁ reached a maximum concentration of 3.8 ± 0.9 ng ml⁻¹ within 35.0 ± 10.2 min and was slowly eliminated from the plasma, with a half-life time (T_1/2) of 931.1 ± 30.8 min. Meanwhile, AFM₁ reached a plateau in plasma (0.5 ± 0.1 ng ml⁻¹) at 4 h after the ingestion. AFB₁ was found in the heart, spleen, lungs, and kidneys at concentrations of 1.6 ± 0.3, 4.1 ± 1.2, 3.3 ± 0.9 and 5.6 ± 1.4 μg kg⁻¹, respectively. AFM₁ was observed in the spleen and kidneys at concentrations of only 0.7 ± 0.2 and 0.8 ± 0.1 μg kg⁻¹, respectively. In conclusion, the in vivo kinetics and biotransformation of AFB₁ in dairy cows were determined using the developed UHPLC-MS/MS method, and the present findings could be helpful in assessing the health risks to consumers.