Physiologically based kinetic modeling of bioactivation and detoxification of the alkenylbenzene methyleugenol in human as compared with rat

Evaluation of the interindividual human variation in bioactivation of methyleugenol using physiologically based kinetic modeling and Monte Carlo simulations

“…In case of UGT1A9 incubations were performed at a protein concentration of 0.5 mg/mL and a substrate concentration ranging from 100 to 4000 μM and in case of UGT2B7 at a protein concentration of 1 mg/mL and a substrate concentration ranging from 250 to 4000 μM. Formation of 1′-hydroxymethyleugenol glucuronide by UGTs was quantified using the same HPLC conditions as previously described for detection of 1′-hydroxymethyleugenol glucuronide formed in incubations with pooled mixed human microsomes (Al-Subeihi et al, 2012).…”

“…The kinetics for oxidation of 1′-hydroxymethyleugenol by individual human liver S9 samples were determined as previously described by Al-Subeihi et al (2012) for determining oxidation by pooled human liver fractions. Incubations were performed using NAD + and NADP + as cofactor and GSH to trap the reactive 1′-oxomethyleugenol at substrate concentrations that ranged from 100 to 3000 μM 1′-hydroxymethyleugenol.…”

“…The amount of 1′-oxomethyleugenol formed in the different samples was corrected for the amount formed in blank incubations. Quantification of GS-1′-oxomethyleugenol formed in these incubations with S9 was performed as described by Al-Subeihi et al (2012).…”

“…The PBK model previously developed for methyleugenol in human (Al-Subeihi et al, 2012) was used in the present study to integrate the kinetic data obtained. The model was adjusted by replacing the kinetic constants for 1′-hydroxylation, epoxidation, and O-demethylation of methyleugenol and the kinetic constants for glucuronidation, oxidation, and sulfonation of 1′-hydroxymethyleugenol, that were previously defined based on incubations with pooled human liver samples, with the kinetic constants obtained in the present study from incubations with recombinant enzymes or individual human liver S9 factions.…”

“…The model was adjusted by replacing the kinetic constants for 1′-hydroxylation, epoxidation, and O-demethylation of methyleugenol and the kinetic constants for glucuronidation, oxidation, and sulfonation of 1′-hydroxymethyleugenol, that were previously defined based on incubations with pooled human liver samples, with the kinetic constants obtained in the present study from incubations with recombinant enzymes or individual human liver S9 factions. All other model parameters as well as the differential equations were kept as they were previously defined (Al-Subeihi et al, 2012). As a first step, the kinetic data obtained were used to simulate 1′-sulfooxymethyleugenol formation in an average individual human subject by taking average relative activity factors for recombinant enzymes into account and the average K m and V max values for sulfonation and oxidation of 1′-hydroxymethyleugenol as obtained in the present study with incubations of individual human liver S9 fractions.…”