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EC number: 242-894-7 | CAS number: 19224-26-1
Table 2. Data Summary: Hepatocyte Stability
Clearance (µl/min/million cells)
Avg % Remaining at Last Point
Propylene Glycol Dibenzoate
Phase I Control
Phase II Control
NR: Not reportable due to no measurable compound after T0 time point
Table 3. Quantitation of Benzoic Acid in Human Hepatocytes
Table 4. Quantitation of Benzoic Acid in Rat Hepatocytes
The objective of this study was to evaluate the rate and completeness of metabolism of Propylene Glycol Dibenzoate in human and rat primary cryopreserved hepatocytes via measurement of the parent compound, and quantitation of Benzoic acid in the culture media post-incubation.
The test article was incubated in duplicate, for each timepoint, with cryopreserved hepatocytes at 37°C. The cells were thawed; viable cells were counted and equilibrated according to the supplier’s directions. After 30 min equilibration at 37°C with gentle agitation, the test article was added to the cell suspension to achieve desired final concentration of 1 µM. The cell suspension was incubated at 37°C. At the indicated times, samples were removed and mixed with an equal volume of ice-cold acetonitrile (containing the IS internal standard propranolol) to stop the reaction and precipitate proteins. Stopped reactions were kept on ice for at least ten minutes. The samples were centrifuged to remove precipitated protein, and supernatants were analyzed by LC/MS/MS to quantify the % parent compound remaining.
Data analysis was done to calculate % parent remaining by assuming zero minute time point peak area ratio (analyte/IS) as 100% and dividing the remaining time point peak area ratios by the zero minute time point peak area ratio value. Data was subjected to a fit first-order decay model to determine half-life. A graph of log (ln) of peak area ratio against time was plotted to calculate the slope. Subsequently, half-life and intrinsic clearance values were calculated.
Propylene Glycol Dibenzoate was rapidly metabolized in both human and rat hepatocytes. The parent compound was not detectable at the 15 minute time point, suggesting complete metabolism by that time point. Based on the rapid nature of the disappearance, a half-life could not be calculated. Benzoic acid was detected at 9.7 mM at the 15 minute time point. While complete metabolism of a dibenzoate compound would be expected to yield a 2:1 molar ratio of benzoic acid:parent compound, the fact that only roughly 50% of the expected levels of benzoic acid were detected may be explained by the observation that the remaining benzoic acid is further metabolized after the 15 minute time point. The most likely explanation for this discrepancy is that the initial levels of benzoic acid upon addition of the parent compound were higher, and 50% metabolism of the benzoic acid occurred between T0 and 15 minutes. Propylene Glycol(PG) was the other metabolic by product that was expected but the laboratory was unable to develop a LC or GCMS method for derivatized or underivatized PG. Two different derivatization procedures (Boronic Acid and Benzoyl Chloride) were unsuccessful.
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