Simultaneous HPLC determination of tolbutamide, phenacetin and their metabolites as markers of cytochromes 1A2 and 2C6/11 in rat liver perfusate

Stereoisomers of octahydrocurcumin, the hydrogenated metabolites of curcumin, display stereoselective activity on the CYP2E1 enzyme in L-02 cells

As the final hydrogenated metabolite of curcumin, octahydrocurcumin (OHC) exhibits increased powerful bioactivities. The chiral and symmetric chemical structure indicated that there were two OHC stereoisomers, (3R,5S)-octahydrocurcumin (Meso-OHC) and (3S,5S)-octahydrocurcumin ((3S,5S)-OHC), which may induce different effects on metabolic enzymes and bioactivities. Thus, we detected OHC stereoisomers from rat metabolites (blood, liver, urine and feces) after oral administration of curcumin. In addition, OHC stereoisomers were prepared and then their different influences on cytochrome P450 enzymes (CYPs) and UDP-glucuronyltransferases (UGTs) in L-02 cells were tested to explore the potential interaction and different bioactivities. Our results proved that curcumin could be metabolised into OHC stereoisomers first. In addition, Meso-OHC and (3S,5S)-OHC exhibited slight induction or inhibition effects on CYP1A2, CYP2A6, CYP2C8, CYP2C9, CYP3A4 and UGTs. Furthermore, Meso-OHC exhibited more intensive inhibition toward CYP2E1 expression than (3S,5S)-OHC, ascribed to the different mode of binding to the enzyme protein (P < 0.05), which finally induced more effective liver protection effects in acetaminophen-induced L-02 cell injury.

Effect of citral on mouse hepatic cytochrome P450 enzymes

CONTEXT

Citral is used as a potential natural treatment for various infectious diseases.

OBJECTIVE

To examine the effect of citral on the mRNA expression and activities of cytochrome P450 (CYP450) enzymes and establish the relationship between citral-induced liver injury and oxidative stress.

MATERIALS AND METHODS

ICR mice were randomly divided into citral (20, 200, and 2000 mg/kglow), Tween-80, and control groups (0.9% saline), 10 mice in each group. The citral-treated groups were intragastrically administered citral for 3 d, control groups treated with 0.5% Tween-80 and 0.9% saline in the same way. Liver injury and CYP450 enzymes were analyzed by analyzing the histopathological changes and the changes of related enzymes.

RESULTS

Citral treatment (2000 mg/kg) for 3 d increased serum glutamic pyruvic transaminase and glutamic oxaloacetic transaminase levels, as well as glutathione, gydroxyl radicals, malonaldehyde and total superoxide dismutase contents, but decreased the content of total antioxidant capacity. In doses of 20 and 200 mg/kg groups mice, the contents of NO were decreased significantly and other changes were similar to the 2000 mg/kg group mice, but the liver damage was most severe in the 2000 mg/kg group. Citral induced the mRNA expression and activities of CYP450 1A2, 2D22, and 2E1 in the liver of mice at doses of 20 and 200 mg/kg. There were no changes in testing indexes in Tween-80 treated group mice. Due to its toxic effects, the CYP induction effect of citral negatively correlated with its dose. Although the mRNA expression of CYP450 3A11 was induced by citral, its activity was not affected by low and moderate doses of citral. CYP450 3A11 activity was significantly decreased by high-dose citral.

CONCLUSIONS

Citral is hepatotoxic and induced oxidative stress in higher dose, which has a negative effect on CYP450 enzymes. These data suggest caution needs to be taken in order to avoid citral-drug interactions in human beings.

Modulation of Rat Hepatic CYP1A and 2C Activity by Honokiol and Magnolol: Differential Effects on Phenacetin and Diclofenac Pharmacokinetics In Vivo

Honokiol (2-(4-hydroxy-3-prop-2-enyl-phenyl)-4-prop-2-enyl-phenol) and magnolol (4-Allyl-2-(5-allyl-2-hydroxy-phenyl)phenol) are the major active polyphenol constituents of Magnolia officinalis (Magnoliaceae) bark, which has been widely used in traditional Chinese medicine (Houpu Tang) for the treatment of various diseases, including anxiety, stress, gastrointestinal disorders, infection, and asthma. The aim of this study was to investigate the direct effects of honokiol and magnolol on hepatic CYP1A and 2C-mediated metabolism in vitro using rat liver microsomes and in vivo using the Sprague-Dawley rat model. Honokiol and magnolol inhibited in vitro CYP1A activity (probe substrate: phenacetin) more potently than CYP2C activity (probe substrate: diclofenac): The mean IC₅₀ values of honokiol for the metabolism of phenacetin and diclofenac were 8.59 μM and 44.7 μM, while those of magnolol were 19.0 μM and 47.3 μM, respectively. Notably, the systemic exposure (AUC and C_max) of phenacetin, but not of diclofenac, was markedly enhanced by the concurrent administration of intravenous honokiol or magnolol. The differential effects of the two phytochemicals on phenacetin and diclofenac in vivo pharmacokinetics could at least be partly attributed to their lower IC₅₀ values for the inhibition of phenacetin metabolism than for diclofenac metabolism. In addition, the systemic exposure, CL, and V_ss of honokiol and magnolol tended to be similar between the rat groups receiving phenacetin and diclofenac. These findings improve our understanding of CYP-mediated drug interactions with M. officinalis and its active constituents.

Assessment of cytochrome P450 inhibition and induction potential of lupeol and betulin in rat liver microsomes

BACKGROUND

Lupeol and betulin are triterpenoids that are majorly found in dietary substances. The aim of present study was to investigate the inhibition and induction potential of lupeol and betulin on cytochrome P450 (CYP)1A2, CYP2C11, CYP2D6 and CYP3A2 activities in rat liver microsomes.

METHODS

The inhibition and induction studies were conducted using ethoxy resorufin-O-deethylase (CYP1A2), tolbutamide hydroxylase (CYP2C9), and midazolam hydroxylase (CYP3A4) activity assays. In vitro inhibition study was evaluated by incubating lupeol and betulin (1, 3, 10, 30 and 100 μM) with rat liver microsomes, and the metabolite formation was analyzed by high-performance liquid chromatography. The induction study was conducted by administering lupeol (20 mg/kg) and betulin (50 mg/kg) intraperitoneally for 14 days to rats followed by liver isolation and microsome preparation.

RESULTS

The IC50 values in inhibition studies were found to be 59.42 μM (CYP1A2), >100 μM (CYP2C11, CYP2D6, CYP3A2) for lupeol, 52.24 μM (CYP1A2), and >100 μM (CYP2C9, CYP2D6, CYP3A2) for betulin. There was no significant modification observed in the CYP450 isoforms, indicating neither inhibition nor induction potential of lupeol and betulin.

CONCLUSIONS

Lupeol and betulin have very low propensity to interact with CYP enzyme, suggesting no CYP inhibitory and inducing potential in rat liver microsomes.

Surface-modified PLGA nanoparticles with chitosan for oral delivery of tolbutamide

The main purpose of present study was to develop novel chitosan-modified polylactic-co-glycolicacid nanoparticles (CS@PLGA NPs) for improving the bio-availability of tolbutamide (TOL). The TOL-loaded CS@PLGA NPs (TOL-CS@PLGA NPs) were fabricated with the solvent evaporation method. The cargo-free CS@PLGA NPs showed a diameter of 228.3±2.5nm monitored with a laser light particlesizer, and the transmission electron microscope (TEM) photographs revealed their "core-shell" structures. The Zeta potential of the original PLGA NPs and the cargo-free CS@PLGA NPs was measured to be -20.2±3.21mV and 24.2±1.1mV, respectively. The changes in Zeta potential indicated the CS chains were coated on the surfaces of the original PLGA NPs. The thermal gravity analysis (TGA) curves suggested that the CS chains improved the thermostability of the original PLGA NPs. The results of cells viability indicated the cargo-free CS@PLGA NPs were nontoxicity. The in vitro release profiles suggested that TOL-CS@PLGA NPs could release TOL in pH 7.4 phosphate buffer solution (PBS) at a sustained manner. Streptozotocin (STZ) was employed to build the diabetic rat models. The physiological changes in the islet β cells confirmed the obtaining of diabetic rats. After treatment by gavage, the TOL-CS@PLGA NPs showed an excellent hypoglycemic effect. Therefore, the TOL-CS@PLGA NPs had a potential application in oral delivery of TOL.

On-Line two dimensional liquid chromatography based on skeleton type molecularly imprinted column for selective determination of sulfonylurea additive in Chinese patent medicines or functional foods

Substandard and counterfeit anti-diabetic medicines directly influence the health and impose a great danger to individual patients and to public health. Counterfeiting has become a serious and underreported problem in the pharmaceutical industry. There are a large number of counterfeit medicines flooded in anti-diabetic markets which effect human health directly and indirectly. Therefore, some novel analytical techniques are necessary to be established for detecting these counterfeit drugs. In this study, a novel skeleton type molecularly imprinted column was successfully prepared. Based on the column, a simple, fast and reliable two-dimensional chromatography analytical system was established for selective determination of the illegal sulfonylurea additive in traditional Chinese patent medicines and functional foods. The developed method was validated. The linearitiesof the method were tested with calibration curves using ten calibration points in the concentration range of 0.25-12.5μg/g. The LODs were 0.0125μg/g and 0.01μg/g for tolbutamide and glibenclamide respectively. The five batches of Chinese patent medicines and dietary supplements obtained from different markets and online websites were tested by the validated method. With good retention time and spectral confirmation, chemical anti-diabetic substances were identified and quantified in traditional Chinese medicine and in dietary supplements.

CdTe quantum dots@luminol for trace-level chemiluminescence sensing of phenacetin based on biological recognition materials

The CL signal was amplified by CRET in CdTe QDs@luminol to improve the sensitivity and CsMG-MIP was introduced to improve the selectivity.

Metabolic interactions of magnolol with cytochrome P450 enzymes: uncompetitive inhibition of CYP1A and competitive inhibition of CYP2C

Magnolol (MAG; 5,5'-diallyl-2,2'-biphenyldiol) is a major bioactive component of Magnolia officinalis. We investigated the metabolic interactions of MAG with hepatic cytochrome P450 monooxygenase (CYP) through in vitro microsomal metabolism study using human (HLM) and rat liver microsomes (RLM). CYP2C and 3A subfamilies were significantly involved in the metabolism of MAG, while CYP1A subfamily was not in HLM and RLM. The relative contribution of phase I enzymes including CYP to the metabolism of MAG was comparable to that of uridine diphosphate glucuronosyltransferase (UGT) in RLM. Moreover, MAG potently inhibited the metabolic activity of CYP1A (IC50 of 1.62 μM) and 2C (IC50 of 5.56 μM), while weakly CYP3A (IC50 of 35.0 μM) in HLM and RLM. By the construction of Dixon plot, the inhibition type of MAG on CYP activity in RLM was determined as follows: uncompetitive inhibitor for CYP1A (Ki of 1.09-12.0 μM); competitive inhibitor for CYP2C (Ki of 10.0-15.2 μM) and 3A (Ki of 93.7-183 μM). Based on the comparison of the current IC50 and Ki values with a previously reported liver concentration (about 13 μM) of MAG after its seven times oral administration at a dose of 50 mg/kg in rats, it is suggested that MAG could show significant inhibition of CYP1A and 2C, but not CYP3A, in the in vivo rat system. These results could lead to further studies in clinically significant metabolism-mediated MAG-drug interactions.

Nonaqueous capillary electrophoresis of dextromethorphan and its metabolites

This study deals with the nonaqueous capillary electrophoretic separation of dextromethorphan and its metabolites using a methanolic background electrolyte. The optimization of separation conditions was performed in terms of the resolution of dextromethorphan and dextrorphan and the effect of separation temperature, voltage, and the characteristics of the background electrolyte were studied. Complete separation of all analytes was achieved in 40 mM ammonium acetate dissolved in methanol. Hydrodynamic injection was performed at 3 kPa for 4 s. The separation voltage was 20 kV accompanied by a low electric current. The ultraviolet detection was performed at 214 nm, the temperature of the capillary was 25°C. These conditions enabled the separation of four analytes plus the internal standard within 9 min. Further, the developed method was validated in terms of linearity, sensitivity, and repeatability. Rat liver perfusate samples were subjected to the nonaqueous capillary electrophoretic method to illustrate its applicability.

The impaired disposition of probe drugs is due to both liver and kidney dysfunctions in CCl(4)-model rats

The carbon tetrachloride (CCl(4))-treated model involving mature Sprague-Dawley rats has been historically relied upon to study liver injury and regeneration and to test drug efficacy and disposition. However, there few studies about phase II metabolic enzymes changes in CCl(4)-model rats. The metabolic and excretion tests of phenacetin and acetaminophen (APAP), and the mRNA test of cytochrome P4501A2 (CYP1A2) and phase II metabolic enzymes [sulfotransferase 1A1 (SULT1A1) and UDP-glucuronosyltransferase 1A6 (UGT1A6)] were studied in model rats after CCl(4) pretreatment. The result showed that the function and structure of liver and kidney was impaired by CCl(4) pretreatment, and a significant difference has been observed in the mRNA content of CYP1A2 (p<0.01) in model group, but there was no significant difference on the mRNA content of SULT1A1 and UGT1A6 in both groups. Compared to the control group, a significant higher content of phenacetin (p<0.01) and sulfate-APAP (AS, p<0.01) was observed in the metabolic tests of phenacetin and APAP. Statistically significant differences in cumulative urinary excretion levels of APAP, AG and AS for CCl(4) model rats were observed also. We have shown that impaired disposition of probe drugs in this model was due to both liver and kidney dysfunction in CCl(4)-model rats and we should consider the development of a new liver damage model without renal impairment.

Effect of vanillin and ethyl vanillin on cytochrome P450 activity in vitro and in vivo

Food safety is of extreme importance to human health. Vanillin and ethyl vanillin are the widely used food additives and spices in foods, beverages, cosmetics and drugs. The objective of the present work was to evaluate the impact of vanillin and ethyl vanillin on the activities of CYP2C9, CYP2E1, CYP3A4, CYP2B6 and CYP1A2 in human liver microsomes (HLM) in vitro, and impact on the activities of CYP1A2, CYP2C, CYP3A and CYP2E1 in rat liver microsomes (RLM) in vivo. The in vitro results demonstrated that vanillin and ethyl vanillin had no significant effect on the activity of five human CYP450 enzymes with concentration ranged from 8 to 128 μM. However, after rats were orally administered vanillin or ethyl vanillin once a day for seven consecutive days, CYP2E1 activity was increased and CYP1A2 activity was decreased in RLM. The in vivo results revealed that drug interaction between vanillin/ethyl vanillin and the CYP2E1/CYP1A2-metabolizing drugs might be possible, and also suggested that the application of the above additives in foods and drugs should not be unlimited so as to avoid the adverse interaction.

Physicochemical characterisation, drug polymer dissolution and in vitro evaluation of phenacetin and phenylbutazone solid dispersions with polyethylene glycol 8000

Poor water solubility leads to low dissolution rate and consequently, it can limit bioavailability. Solid dispersions, where the drug is dispersed into an inert, hydrophilic polymer matrix can enhance drug dissolution. Solid dispersions were prepared using phenacetin and phenylbutazone as model drugs with polyethylene glycol (PEG) 8000 (carrier), by melt fusion method. Phenacetin and phenylbutazone displayed an increase in the dissolution rate when formulated as solid dispersions as compared with their physical mixture and drug alone counterparts. Characterisation of the solid dispersions was performed using differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). DSC studies revealed that drugs were present in the amorphous form within the solid dispersions. FTIR spectra for the solid dispersions of drugs suggested that there was a lack of interaction between PEG 8000 and the drug. However, the physical mixture of phenacetin with PEG 8000 indicated the formation of hydrogen bond between phenacetin and the carrier. Permeability of phenacetin and phenylbutazone was higher for solid dispersions as compared with that of drug alone across Caco-2 cell monolayers. Permeability studies have shown that both phenacetin and phenylbutazone, and their solid dispersions can be categorised as well-absorbed compounds.