Figure 6. 2-OPP is formed from P6C and acetoacetate (AcAc).

Upon incubation of 1 mM P6C with 1 mM AcAc in different matrices — (A) H₂O, (B) PBS, (C) control plasma, and (D) control urine — 2-OPP formation was observed at elevated levels. Elevated 2-OPP formation was also observed upon incubation of 1 mM P6C with ketotic plasma (E) and urine (F). In the negative control incubation in plasma, including P6C but without the addition of AcAc, significantly lower 2-OPP signals were detected (G). The y axis represents relative NGMS intensity (10⁴ or 10⁶ scale), and the x axis represents RT (minutes). (H) The proposed chemical reaction for the formation of 2-OPP from AcAc and P6C (P6C is formed in equilibrium from α-AASA).