2.4. In vitro Stability of Biosynthesized Acyl Glucuronides

The biosynthesized acyl glucuronides were lyophilized using Labconco lyophilizer (Kansas City, MO). The residues containing the acyl glucuronides were re-suspended in 1.5 mL of 0.1 M KH₂PO₄ buffer (pH 7.4) and 300 µL were immediately transferred to another clean vial containing 300 µL of acetonitrile with 0 or 1% formic acid to make the 0 hour time point. Subsequent time points at 1, 2, and 4 hours were processed in the same way as the 0 hour time point. All time points were analyzed by Orbitrap Elite MSⁿ instrument (Thermo Fisher Scientific, Waltham, MA) without any further treatment.