Interactions between cyazofamid and human drug transporters.

We aimed to investigate the intestinal permeability and interaction of cyazofamid with clinically important transporters. The intestinal permeability of cyazofamid was low (0.21 ± 0.02 cm/s), and it is a substrate for P-glycoprotein (P-gp) with a Km value of 83.1 µM, indicated that P-gp in the intestinal lumen could serve as a protective barrier to this fungicide. Cyazofamid was not a substrate for clinically important transporters. However, cyazofamid inhibited organic cation transporter 3 (OCT3) and OAT1, with IC50 values of 1.54 and 17.3 µM, respectively, but could not result in OAT3- and OAT1-mediated cyazofamid-drug interactions because of its low plasma concentration. Cyazofamid poorly interacted with OCT1, OCT2, organic anion transporting polypeptide 1B1 (OATP1B1), OATP1B3, P-gp, breast cancer resistance-related protein, and multidrug resistance-related protein 2. In conclusion, the interactions of cyazofamid with human drug transporters have been evaluated as part of the safety assessment. Given its low intestinal permeability and poor interaction with human drug transporters, cyazofamid might not cause serious toxicity or adverse events.

Absorption, metabolism, and excretion of [14C]evogliptin tartrate in male rats and dogs.

The objective of this study was to determine the absorption, excretion, and metabolism of a novel, oral antihyperglycemic drug, evogliptin, in male rats and dogs. Plasma, urine, feces, and expired air samples were collected after a single oral dose administration of [14C]evogliptin, samples were analyzed by measuring overall radioactivity levels using high-performance liquid chromatography (HPLC), and radioactivity levels were measured by utilizing LC-tandem mass spectrometry (LC-MS/MS). The total amounts of radioactivity excreted in urine, feces, and expired air up to 168 h after administration of [14C]evogliptin tartrate to rats (30 mg evogliptin/kg) and dogs (10 mg evogliptin/kg) were 96.7% and 96.8% of initial doses administered, respectively. The extent of urinary and fecal excretion in the rat up to 168 h constituted 29.7% and 66.5% of the given dose, respectively; and in dog was 43.3% and 53.5%, respectively. A total of 23 possible metabolites were detected with radiochromatograms of plasma, urinary, and fecal samples, but only the structures of 12 metabolites were identified via LC-MS/MS analysis. Evogliptin was the major component. Regarding the total radiochromatographic peak areas, peaks 9 (evogliptin acid) and 11 (hydroxyevogliptin) were the major metabolites in rats, and peaks 8 [4(S)-hydroxyevogliptin glucuronide], 15 [4(S)-hydroxyevogliptin], and 17 [4(R)-hydroxyevogliptin] were the predominant metabolites in dogs. Data demonstrated that evogliptin was the major component excreted in urine and feces of rats and dogs, but the metabolite profiles varied between species.

Inhibitory Effects of Dimethyllirioresinol, Epimagnolin A, Eudesmin, Fargesin, and Magnolin on Cytochrome P450 Enzyme Activities in Human Liver Microsomes.

Magnolin, epimagnolin A, dimethyllirioresinol, eudesmin, and fargesin are pharmacologically active tetrahydrofurofuranoid lignans found in Flos Magnoliae. The inhibitory potentials of dimethyllirioresinol, epimagnolin A, eudesmin, fargesin, and magnolin on eight major human cytochrome P450 (CYP) enzyme activities in human liver microsomes were evaluated using liquid chromatography-tandem mass spectrometry to determine the inhibition mechanisms and inhibition potency. Fargesin inhibited CYP2C9-catalyzed diclofenac 4'-hydroxylation with a Ki value of 16.3 µM, and it exhibited mechanism-based inhibition of CYP2C19-catalyzed [S]-mephenytoin 4'-hydroxylation (Ki, 3.7 µM; kinact, 0.102 min-1), CYP2C8-catalyzed amodiaquine N-deethylation (Ki, 10.7 µM; kinact, 0.082 min-1), and CYP3A4-catalyzed midazolam 1'-hydroxylation (Ki, 23.0 µM; kinact, 0.050 min-1) in human liver microsomes. Fargesin negligibly inhibited CYP1A2-catalyzed phenacetin O-deethylation, CYP2A6-catalyzed coumarin 7-hydroxylation, CYP2B6-catalyzed bupropion hydroxylation, and CYP2D6-catalyzed bufuralol 1'-hydroxylation at 100 µM in human liver microsomes. Dimethyllirioresinol weakly inhibited CYP2C19 and CYP2C8 with IC50 values of 55.1 and 85.0 µM, respectively, without inhibition of CYP1A2, CYP2A6, CYP2B6, CYP2C9, CYP2D6, and CYP3A4 activities at 100 µM. Epimagnolin A, eudesmin, and magnolin showed no the reversible and time-dependent inhibition of eight major CYP activities at 100 µM in human liver microsomes. These in vitro results suggest that it is necessary to investigate the potentials of in vivo fargesin-drug interaction with CYP2C8, CYP2C9, CYP2C19, and CYP3A4 substrates.

Inhibitory Effects of Aschantin on Cytochrome P450 and Uridine 5'-diphospho-glucuronosyltransferase Enzyme Activities in Human Liver Microsomes.

Aschantin is a bioactive neolignan found in Magnolia flos with antiplasmodial, Ca(2+)-antagonistic, platelet activating factor-antagonistic, and chemopreventive activities. We investigated its inhibitory effects on the activities of eight major human cytochrome P450 (CYP) and uridine 5'-diphospho-glucuronosyltransferase (UGT) enzymes of human liver microsomes to determine if mechanistic aschantin-enzyme interactions were evident. Aschantin potently inhibited CYP2C8-mediated amodiaquine N-de-ethylation, CYP2C9-mediated diclofenac 4'-hydroxylation, CYP2C19-mediated [S]-mephenytoin 4'-hydroxylation, and CYP3A4-mediated midazolam 1'-hydroxylation, with Ki values of 10.2, 3.7, 5.8, and 12.6 µM, respectively. Aschantin at 100 µM negligibly inhibited CYP1A2-mediated phenacetin O-de-ethylation, CYP2A6-mediated coumarin 7-hydroxylation, CYP2B6-mediated bupropion hydroxylation, and CYP2D6-mediated bufuralol 1'-hydroxylation. At 200 µM, it weakly inhibited UGT1A1-catalyzed SN-38 glucuronidation, UGT1A6-catalyzed N-acetylserotonin glucuronidation, and UGT1A9-catalyzed mycophenolic acid glucuronidation, with IC50 values of 131.7, 144.1, and 71.0 µM, respectively, but did not show inhibition against UGT1A3, UGT1A4, or UGT2B7 up to 200 µM. These in vitro results indicate that aschantin should be examined in terms of potential interactions with pharmacokinetic drugs in vivo. It exhibited potent mechanism-based inhibition of CYP2C8, CYP2C9, CYP2C19, and CYP3A4.

Comparative metabolism of honokiol in mouse, rat, dog, monkey, and human hepatocytes.

Honokiol has antitumor, antioxidative, anti-inflammatory, and antithrombotic effects. Here we aimed to identify the metabolic profile of honokiol in mouse, rat, dog, monkey, and human hepatocytes and to characterize the enzymes responsible for the glucuronidation and sulfation of honokiol. Honokiol had a high hepatic extraction ratio in all five species, indicating that it was extensively metabolized. A total of 32 metabolites, including 17 common and 15 different metabolites, produced via glucuronidation, sulfation, and oxidation of honokiol allyl groups were tentatively identified using liquid chromatography-high resolution quadrupole Orbitrap mass spectrometry. Glucuronidation of honokiol to M8 (honokiol-4-glucuronide) and M9 (honokiol-2'-glucuronide) was the predominant metabolic pathway in hepatocytes of all five species; however, interspecies differences between 4- and 2'-glucuronidation of honokiol were observed. UGT1A1, 1A8, 1A9, 2B15, and 2B17 played major roles in M8 formation, whereas UGT1A7 and 1A9 played major roles in M9 formation. Human cDNA-expressed SULT1C4 played a major role in M10 formation (honokiol-2'-sulfate), whereas SULT1A1*1, 1A1*2, and 1A2 played major roles in M11 formation (honokiol-4-sulfate). In conclusion, honokiol metabolism showed interspecies differences.

In Vitro Metabolic Pathways of the New Anti-Diabetic Drug Evogliptin in Human Liver Preparations.

Evogliptin ((R)-4-((R)-3-amino-4-(2,4,5-trifluorophenyl)butanoyl)-3-(tert-butoxymethyl)-piperazin-2-one), is a new dipeptidyl peptidase IV inhibitor used for the treatment of type II diabetes mellitus. The in vitro metabolic pathways of evogliptin were identified in human hepatocytes, liver microsomes, and liver S9 fractions using liquid chromatography-Orbitrap mass spectrometry (LC-HRMS). Five metabolites of evogliptin-4-oxoevogliptin (M1), 4(S)-hydroxyevogliptin (M2), 4(R)-hydroxyevogliptin (M3), 4(S)-hydroxyevogliptin glucuronide (M4), and evogliptin N-sulfate (M5)-were identified in human liver preparations by comparison with authentic standards. We characterized the cytochrome P450 (CYP) enzymes responsible for evogliptin hydroxylation to 4(S)-hydroxyevogliptin (M2) and 4(R)-hydroxyevogliptin (M3) and the UGT enzymes responsible for glucuronidation of 4(S)-hydroxyevogliptin (M2) to 4(S)-hydroxy-evogliptin glucuronide (M4). CYP3A4/5 played the major role in the hydroxylation of evogliptin to 4(S)-hydroxyevogliptin (M2) and 4(R)-hydroxyevogliptin (M3). Glucuronidation of 4(S)-hydroxy-evogliptin (M2) to 4(S)-hydroxyevogliptin glucuronide (M4) was catalyzed by the enzymes UGT2B4 and UGT2B7. These results suggest that the interindividual variability in the metabolism of evogliptin in humans is a result of the genetic polymorphism of the CYP and UGT enzymes responsible for evogliptin metabolism.

Role of cytochrome P450 and UDP-glucuronosyltransferases in metabolic pathway of homoegonol in human liver microsomes.

Homoegonol is being evaluated for the development of a new antiasthmatic drug. Based on a pharmacokinetic study of homoegonol in rats, homoegonol is almost completely eliminated via metabolism, but no study on its metabolism has been reported in animals and humans. Incubation of homoegonol in human liver microsomes in the presence of the reduced form of nicotinamide adenine dinucleotide phosphate and UDP-glucuronic acid resulted in the formation of five metabolites: 4-O-demethylhomoegonol (M1), hydroxyhomoegonol (M2 and M3), 4-O-demethylhomoegonol glucuronide (M4), and homoegonol glucuronide (M5). We characterized the cytochrome P450 (CYP) and UDP-glucuronosyltransferase (UGT) enzymes responsible for homoegonol metabolism using human liver microsomes, and cDNA-expressed CYP and UGT enzymes. CYP1A2 played a more prominent role than CYP3A4 and CYP2D6 in the 4-O-demethylation of homoegonol to M1. CYP3A4 was responsible for the hydroxylation of homoegonol to M2. The hydroxylation of homoegonol to M3 was insufficient to characterize CYP enzymes. Glucuronidation of homoegonol to M5 was mediated by UGT1A1, UGT1A3, UGT1A4, and UGT2B7 enzymes, whereas M4 was formed from 4-O-demethylhomoegonol by UGT1A1, UGT1A8, UGT1A10, and UGT2B15 enzymes.

Organic anion transporter 3- and organic anion transporting polypeptides 1B1- and 1B3-mediated transport of catalposide.

We investigated the in vitro transport characteristics of catalposide in HEK293 cells overexpressing organic anion transporter 1 (OAT1), OAT3, organic anion transporting polypeptide 1B1 (OATP1B1), OATP1B3, organic cation transporter 1 (OCT1), OCT2, P-glycoprotein (P-gp), and breast cancer resistance protein (BCRP). The transport mechanism of catalposide was investigated in HEK293 and LLC-PK1 cells overexpressing the relevant transporters. The uptake of catalposide was 319-, 13.6-, and 9.3-fold greater in HEK293 cells overexpressing OAT3, OATP1B1, and OATP1B3 transporters, respectively, than in HEK293 control cells. The increased uptake of catalposide via the OAT3, OATP1B1, and OATP1B3 transporters was decreased to basal levels in the presence of representative inhibitors such as probenecid, furosemide, and cimetidine (for OAT3) and cyclosporin A, gemfibrozil, and rifampin (for OATP1B1 and OATP1B3). The concentration-dependent OAT3-mediated uptake of catalposide revealed the following kinetic parameters: Michaelis constant (K m) =41.5 µM, maximum uptake rate (V max) =46.2 pmol/minute, and intrinsic clearance (CL int) =1.11 µL/minute. OATP1B1- and OATP1B3-mediated catalposide uptake also showed concentration dependency, with low CL int values of 0.035 and 0.034 µL/minute, respectively. However, the OCT1, OCT2, OAT1, P-gp, and BCRP transporters were apparently not involved in the uptake of catalposide into cells. In addition, catalposide inhibited the transport activities of OAT3, OATP1B1, and OATP1B3 with half-maximal inhibitory concentration values of 83, 200, and 235 µM, respectively. However, catalposide did not significantly inhibit the transport activities of OCT1, OCT2, OAT1, P-gp, or BCRP. In conclusion, OAT3, OATP1B1, and OATP1B3 are major transporters that may regulate the pharmacokinetic properties and may cause herb-drug interactions of catalposide, although their clinical relevance awaits further evaluation.

Metabolism-mediated drug interaction potential of HS-23, a new herbal drug for the treatment of sepsis in human hepatocytes and liver microsomes.

HS-23, an extract of the dried flower buds of Lonicera japonica, is a new botanical drug currently being evaluated in a phase I clinical study in Korea for the treatment of sepsis. The in vitro induction and inhibition potentials of HS-23 on the drug-metabolizing enzymes using human hepatocytes and liver microsomes were assessed to evaluate herb-drug interaction according to botanical drug guideline and drug interaction guidance of FDA. HS-23 slightly inhibited CYP2A6, CYP2B6, CYP2C9, CYP2C19, and CYP3A4 enzyme activities in human liver microsomes with IC50 values of 80.6, 160.7, 169.5, 85.4, and 76.6 µg/mL, respectively. HS-23 showed negligible inhibition of CYP1A2, CYP2C8, CYP2D6, UGT1A1, UGT1A4, UGT1A9, and UGT2B7 activities in human liver microsomes. Based on these results, HS-23 may not inhibit the metabolism of CYP2A6, CYP2B6, CYP2C9, CYP2C19, and CYP3A4-catalyzed drugs in humans. HS-23 did not affect the mRNA expression of CYP1A2, CYP2B6, and CYP3A4 after 48 h treatment at three concentrations (0.5, 5, and 50 µg/mL) in three independent human hepatocytes, indicating that HS-23 has no effect on herb-drug interactions that up- or down-regulate CYP1A2, CYP2B6, and CYP3A4. These results indicate that the administration of HS-23 in human may not cause clinically relevant inhibition and induction of these cytochrome P450 (CYP) and UDP-glucuronosyltransferase (UGT) enzymes and HS-23 may be promising therapeutic agent for treatment of sepsis.

Effect of honokiol on the induction of drug-metabolizing enzymes in human hepatocytes.

Honokiol, 2-(4-hydroxy-3-prop-2-enyl-phenyl)-4-prop-2-enyl-phenol, an active component of Magnolia officinalis and Magnolia grandiflora, exerts various pharmacological activities such as antitumorigenic, antioxidative, anti-inflammatory, neurotrophic, and antithrombotic effects. To investigate whether honokiol acts as a perpetrator in drug interactions, messenger ribonucleic acid (mRNA) levels of phase I and II drug-metabolizing enzymes, including cytochrome P450 (CYP), UDP-glucuronosyltransferase (UGT), and sulfotransferase 2A1 (SULT2A1), were analyzed by real-time reverse transcription polymerase chain reaction following 48-hour honokiol exposure in three independent cryopreserved human hepatocyte cultures. Honokiol treatment at the highest concentration tested (50 µM) increased the CYP2B6 mRNA level and CYP2B6-catalyzed bupropion hydroxylase activity more than two-fold in three different hepatocyte cultures, indicating that honokiol induces CYP2B6 at higher concentrations. However, honokiol treatment (0.5-50 µM) did not significantly alter the mRNA levels of phase I enzymes (CYP1A2, CYP3A4, CYP2C8, CYP2C9, and CYP2C19) or phase II enzymes (UGT1A1, UGT1A4, UGT1A9, UGT2B7, and SULT2A1) in cryopreserved human hepatocyte cultures. CYP1A2-catalyzed phenacetin O-deethylase and CYP3A4-catalyzed midazolam 1'-hydroxylase activities were not affected by 48-hour honokiol treatment in cryopreserved human hepatocytes. These results indicate that honokiol is a weak CYP2B6 inducer and is unlikely to increase the metabolism of concomitant CYP2B6 substrates and cause pharmacokinetic-based drug interactions in humans.

Inhibitory effects of cedrol, ß-cedrene, and thujopsene on cytochrome P450 enzyme activities in human liver microsomes.

Cedrol, ß-cedrene, and thujopsene are bioactive sesquiterpenes found in cedar essential oil and exert antiseptic, anti-inflammatory, antispasmodic, tonic, astringent, diuretic, sedative, insecticidal, and antifungal activities. These compounds are used globally in traditional medicine and cosmetics. The aim of this study was to investigate the inhibitory effects of cedrol, ß-cedrene, and thujopsene on the activities of eight major human cytochrome P-450 (CYP) enzymes using human liver microsomes to assess potential ß-cedrene-, cedrol-, and thujopsene-drug interactions. Cedrol, ß-cedrene, and thujopsene were found to be potent competitive inhibitors of CYP2B6-mediated bupropion hydroxylase with inhibition constant (Ki) values of 0.9, 1.6, and 0.8 µM, respectively, comparable with that of a selective CYP2B6 inhibitor, thioTEPA (Ki, 2.9 µM). Cedrol also markedly inhibited CYP3A4-mediated midazolam hydroxylation with a Ki value of 3.4 µM, whereas ß-cedrene and thujopsene moderately blocked CYP3A4. Cedrol, ß-cedrene, and thujopsene at 100 µM negligibly inhibited CYP1A2, CYP2A6, and CYP2D6 activities. Only thujopsene was found to be a mechanism-based inhibitor of CYP2C8, CYP2C9, and CYP2C19. Cedrol and thujopsene weakly inhibited CYP2C8, CYP2C9, and CYP2C19 activities, but ß-cedrene did not. These in vitro results indicate that cedrol, ß-cedrene, and thujopsene need to be examined for potential pharmacokinetic drug interactions in vivo due to their potent inhibition of CYP2B6 and CYP3A4.

Evaluation of the transporter-mediated herb-drug interaction potential of DA-9801, a standardized dioscorea extract for diabetic neuropathy, in human in vitro and rat in vivo.

BACKGROUND: Drug transporters play important roles in the absorption, distribution, and elimination of drugs and thereby, modulate drug efficacy and toxicity. With a growing use of poly pharmacy, concurrent administration of herbal extracts that modulate transporter activities with drugs can cause serious adverse reactions. Therefore, prediction and evaluation of drug-drug interaction potential is important in the clinic and in the drug development process. DA-9801, comprising a mixed extract of Dioscoreae rhizoma and Dioscorea nipponica Makino, is a new standardized extract currently being evaluated for diabetic peripheral neuropathy in a phase II clinical study. METHOD: The inhibitory effects of DA-9801 on the transport functions of organic cation transporter (OCT)1, OCT2, organic anion transporter (OAT)1, OAT3, organic anion transporting polypeptide (OATP)1B1, OATP1B3, P-glycoprotein (P-gp), and breast cancer resistance protein (BCRP) were investigated in HEK293 or LLC-PK1 cells. The effects of DA-9801 on the pharmacokinetics of relevant substrate drugs of these transporters were also examined in vivo in rats. RESULTS: DA-9801 inhibited the in vitro transport activities of OCT1, OCT2, OAT3, and OATP1B1, with IC50 values of 106, 174, 48.1, and 273 µg/mL, respectively, while the other transporters were not inhibited by 300 µg/mL DA-9801. To investigate whether this inhibitory effect of DA-9801 on OCT1, OCT2, and OAT3 could change the pharmacokinetics of their substrates in vivo, we measured the pharmacokinetics of cimetidine, a substrate for OCT1, OCT2, and OAT3, and of furosemide, a substrate for OAT1 and OAT3, by co-administration of DA-9801 at a single oral dose of 1,000 mg/kg. Pre-dose of DA-9801 5 min or 2 h prior to cimetidine administration decreased the Cmax of cimetidine in rats. However, DA-9801 did not affect the elimination parameters such as half-life, clearance, or amount excreted in the urine, suggesting that it did not inhibit elimination process of cimetidine, which is governed by OCT1, OCT2, and OAT3. Moreover, DA-9801 did not affect the pharmacokinetic characteristics of furosemide, as evidenced by its unchanged pharmacokinetic parameters. CONCLUSION: Inhibitory effects of DA-9801 on OCT1, OCT2, and OAT3 observed in vitro may not necessarily translate into in vivo herb-drug interactions in rats even at its maximum effective dose.

Quantification of homoegonol in rat plasma using liquid chromatography-tandem mass spectrometry and its pharmacokinetics application.

Homoegonol is a biologically active neolignan isolated from Styrax species with cytotoxic, antimicrobial, anti-inflammatory and anti-asthma activities. For the quantification of homoegonol in rat plasma, a selective and sensitive liquid chromatography-tandem mass spectrometric method was developed and validated for the first time using protein precipitation with methanol as a sample clean-up procedure. The analytes were separated in an Atlantis dC18 column using a gradient elution of methanol and 0.1% formic acid, and mass-to-charge ratios were determined in selective reaction monitoring mode using tandem mass spectrometry with m/z 343.12 > 296.97 for homoegonol and m/z 517.30 > 282.90 for udenafil (internal standard). The standard curve was linear over the concentration ranges of 1 - 500 ng/mL using a 30 µL rat plasma sample. The coefficient of variation and relative error for intra- and inter-assay at four quality control levels were 3.9-10.0 and -3.3-2.7%, respectively. The overall recovery of homoegonol from rat plasma using protein precipitation was 99.7 ± 7.7%. The pharmacokinetics parameters of homoegonol were dose-independent after both intravenous (1, 2.5 and 5 mg/kg doses) and oral (5, 10 and 20 mg/kg doses) administration in male Sprague-Dawley rats.

Effect of honokiol on cytochrome P450 and UDP-glucuronosyltransferase enzyme activities in human liver microsomes.

Honokiol is a bioactive component isolated from the medicinal herbs Magnolia officinalis and Magnolia grandiflora that has antioxidative, anti-inflammatory, antithrombotic, and antitumor activities. The inhibitory potentials of honokiol on eight major human cytochrome P450 (CYP) enzymes 1A2, 2A6, 2B6, 2C8, 2C9, 2C19, 2D6, and 3A4, and four UDP-glucuronosyltransferases (UGTs) 1A1, 1A4, 1A9, and 2B7 in human liver microsomes were investigated using liquid chromatography-tandem mass spectrometry. Honokiol strongly inhibited CYP1A2-mediated phenacetin O-deethylation, CYP2C8-mediated amodiaquine N-deethylation, CYP2C9-mediated diclofenac 4-hydroxylation, CYP2C19-mediated [S]-mephenytoin 4-hydroxylation, and UGT1A9-mediated propofol glucuronidation with K(i) values of 1.2, 4.9, 0.54, 0.57, and 0.3 µM, respectively. Honokiol also moderately inhibited CYP2B6-mediated bupropion hydroxylation and CYP2D6-mediated bufuralol 1'-hydroxylation with K(i) values of 17.5 and 12.0 µM, respectively. These in vitro results indicate that honokiol has the potential to cause pharmacokinetic drug interactions with other co-administered drugs metabolized by CYP1A2, CYP2C8, CYP2C9, CYP2C19, and UGT1A9.

Evaluation of DA-9801, a new herbal drug for diabetic neuropathy, on metabolism-mediated interaction.

DA-9801, the mixture extract of Dioscoreae rhizoma and Dioscorea nipponica Makino, is a new herbal drug currently being evaluated in a phase II clinical study for the treatment of diabetic peripheral neuropathy in Korea. The inhibitory potentials of DA-9801, D. rhizoma extract, D. nipponica Makino extract, and dioscin, an active component of DA-9801, on eight human cytochrome P450 (CYP) enzymes and four UDP-glucuronosyltransferase (UGT) enzymes were investigated in human liver microsomes using liquid chromatography-tandem mass spectrometry. DA-9801 showed slight inhibition of CYP1A2, CYP2C8, UGT1A1, and UGT1A9 enzyme activities with IC(50) values of 396.4, 449.9, 226.0, and 408.8 µg/mL, respectively. D. rhizoma extract showed negligible inhibition of CYP and UGT activities, but D. nipponica extract slightly inhibited CYP1A2, CYP2C8, CYP2C9, UGT1A1, and UGT1A9 activities with IC(50) values of 264.2, 237.1, 206.8, 302.4, and 383.1 µg/mL, respectively. DA-9801 showed volume per dose index values of 0.44-0.88 L for a 200-mg dose, suggesting that they may not cause the inhibition of the metabolism of CYP1A2, CYP2C8, UGT1A1, and UGT1A9-catalyzed drugs in humans. These results suggest that the administration of DA-9801 in human may not cause clinically relevant inhibition of these enzymes.

In vitro and in vivo metabolism of verproside in rats.

Verproside, a catalpol derivative iridoid glycoside isolated from Pseudolysimachion rotundum var. subintegrum, is a biologically active compound with anti-inflammatory, antinociceptic, antioxidant, and anti-asthmatic properties. Twenty-one metabolites were identified in bile and urine samples obtained after intravenous administration of verproside in rats using liquid chromatography-quadrupole Orbitrap mass spectrometry. Verproside was metabolized by O-methylation, glucuronidation, sulfation, and hydrolysis to verproside glucuronides (M1 and M2), verproside sulfates (M3 and M4), picroside II (M5), M5 glucuronide (M7), M5 sulfate (M9), isovanilloylcatalpol (M6), M6 glucuronide (M8), M6 sulfate (M10), 3,4-dihydroxybenzoic acid (M11), M11 glucuronide (M12), M11 sulfates (M13 and M14), 3-methyoxy-4-hydroxybenzoic acid (M15), M15 glucuronides (M17 and M18), M15 sulfate (M20), 3-hydroxy-4-methoxybenzoic acid (M16), M16 glucuronide (M19), and M16 sulfate (M21). Incubation of verproside with rat hepatocytes resulted in thirteen metabolites (M1-M11, M13, and M14). Verproside sulfate, M4 was a major metabolite in rat hepatocytes. After intravenous administration of verproside, the drug was recovered in bile (0.77% of dose) and urine (4.48% of dose), and O-methylation of verproside to picroside II (M5) and isovanilloylcatalpol (M6) followed by glucuronidation and sulfation was identified as major metabolic pathways compared to glucuronidation and sulfation of verproside in rats.