Activities of hepatic cytosol enzymes involved in UDP-g1ucuronic acid synthesis as well as in glutathione reduction and conjugation systems were determined following administrations of butylated hydroxyanisole (approximately 5 mmol/kg body weight/day) and of equimolar intake doses of its structural anglogs. These compounds included the multi-functional group side chain compounds (t-butyl hydroquinone, 4-hydroxy- anisole, hydroquinone, benzoquinone) and the mono-functional side chain compounds (t-butyl benzene, anisole, phenol). They were administered to mice for 10 days either by mixing them in the diet or by oral intubations. Results showed that glutathione Stransferase activities were markedly increased by all tested compounds except for the t-butyl benzene. Activities of glutathione reductase and glucose 6-phosphate dehydrogenase were increased together on1y by BHA and t-butyl hydroguinone. UDP-glucose dehydrogenase and NADH:quinone reductase activities were significantly elevated by the multi-functional side chain compounds, but not by the mono-functional analogs. The relations between chemical structures of tested BHA analogs and elevations of the measured hepatic cytosol conjugation (detoxification) system enzyme activities for the metabolism and excretion of BHA analogs are discussed.
Animal ; Anisoles/metabolism* ; Butylated Hydroxyanisole/analogs & derivatives ; Butylated Hydroxyanisole/metabolism* ; Cytosol/enzymology* ; Glutathione/metabolism* ; Mice ; Uridine Diphosphate Glucuronic Acid/biosynthesis* ; Uridine Diphosphate Sugars/biosynthesis*

The metabolic characteristics of ligustrazin (TMPz) in liver microsomes were investigated in the present study. The reaction phenotyping of TMPz metabolism was also identified by in vitro assessment using recombinant human cytochrome P450 enzymes (CYP) and UDP glucuronosyltransferases (UGT). TMPz was incubated at 37 degrees C with human (HLM) and rat liver microsomes (RLM) in the presence of different co-factors. The metabolic stability and enzyme kinetics of TMPz were studied by determining its remaining concentrations with a LC-MS/MS method. TMPz was only metabolically eliminated in the microsomes with NADPH or NADPH+UDPGA. In the HLM and RLM with NADPH+UDPGA, t1/2, K(m) and V(max) of TMPz were 94.24 +/- 4.53 and 105.07 +/- 9.44 min, 22.74 +/- 1.89 and 33.09 +/- 2.74 micromol x L(-1), 253.50 +/- 10.06 and 190.40 +/- 8.35 nmol x min(-1) x mg(-1) (protein), respectively. TMPz showed a slightly higher metabolic rate in HLM than that in RLM. Its primary oxidative metabolites, 2-hydroxymethyl-3, 5, 6-trimethylpyrazine (HTMP), could undergo glucuronide conjugation. The CYP reaction phenotyping of TMPz metabolism was identified using a panel of recombinant CYP isoforms (rCYP) and specific CYP inhibitors in HLM. CYP1A2, 2C9 and 3A4 were found to be the major CYP isoforms involved in TMPz metabolism. Their individual contributions were assessed b) using the method of the total normalized rate to be 19.32%, 27.79% and 52.90%, respectively. It was observed that these CYP isoforms mediated the formation of HTMP in rCYP incubation. The UGT reaction phenotyping of HTMP glucuronidation was also investigated preliminarily by using a panel of 6 UGT isoforms (rUGT). UGT1A1, 1A4 and 1A6 were the predominant isoforms mediated the HTMP glucuronidation. The results above indicate that the metabolism of TMPz involves multiple enzymes mediated phase I and phase II reactions.
Animals ; Cytochrome P-450 CYP1A2 ; metabolism ; Cytochrome P-450 CYP2C9 ; metabolism ; Cytochrome P-450 CYP3A ; metabolism ; Cytochrome P-450 Enzyme Inhibitors ; Cytochrome P-450 Enzyme System ; metabolism ; Drug Interactions ; Glucuronosyltransferase ; metabolism ; Humans ; Ligusticum ; chemistry ; Microsomes, Liver ; enzymology ; NADP ; metabolism ; pharmacology ; Pyrazines ; metabolism ; pharmacokinetics ; Rats ; Uridine Diphosphate Glucuronic Acid ; metabolism ; pharmacology