Determination of aflatoxin concentration by UPLC-MS/MS

At each time point, the cultured A. oxyphylla samples were prepared for aflatoxin (AFB₁, AFB₂, AFG₁ and AFG₂) analysis by UPLC-MS/MS according to the reported procedure and methods (Zhao et al. 2017). One gram of ground powder was placed into a 15-mL polycarbonate centrifuge tube, and was extracted with 4 mL of ACN-water-acetic acid (79:20:1, v/v/v). The tube was tightly capped and vortexed for 1.0 min, and then was placed into an ultrasonic bath at 40 °C for 20 min. The extracts were subsequently centrifuged for 15 min at 12,000 rpm. The supernatant was filtered through a 0.22-μm filter for UPLC-MS/MS analysis.