Exploring the possible metabolism mediated interaction of Glycyrrhiza glabra extract with CYP3A4 and CYP2D6

The rhizome of Glycyrrhiza glabra L. (licorice) is used very widely in Indian and Chinese traditional medicine, and it is a popular flavor ingredient of drinks, sweets and candies. Its medicinal uses include treating bronchitis, dry cough, respiratory infections, liver disorders and diabetes. Glycyrrhizin is normally considered to be its biologically active marker, so a rapid RP‐HPLC method was developed for the quantitative estimation of glycyrrhizin in the extract. The effect of the standardized extract and its marker on drug metabolizing enzymes was evaluated through CYP3A4 and CYP2D6 inhibition assays to evaluate the safety through its drug interaction potential. The inhibition of CYP3A4 and CYP2D6 isozymes was analysed by the fluorescent product formation method. In the CYP450‐CO assay, the interaction potential of the standardized extract and pooled microsomes (percentage inhibition 23.23 ± 1.84%), was found to be less than the standard inhibitor. In the fluorimetric assay, G. glabra extracts showed higher IC₅₀ values than their positive inhibitors, ketoconazole and quinidine for CYP3A4 and CYP2D6, respectively. Furthermore, the interaction potential of the plant extract was greater than the pure compound. The results demonstrate that G. glabra and its principle bioactive compound, glycyrrhizin, when co‐administered with conventional medicines showed only a weak interaction potential with drug metabolizing enzymes. Copyright © 2011 John Wiley & Sons, Ltd.     

In vitro Inhibition of Human CYP1A2, CYP2D6, and CYP3A4 by Six Herbs Commonly Used in Pregnancy

Black elderberry, cranberry, fennel, ginger, horsetail, and raspberry leaf, herbs frequently used in pregnancy, were investigated for their in vitro CYP1A2, 2D6, and 3A4 inhibitory potential. Aqueous or ethanolic extracts were made from commercially available herbal products, and incubations were performed with recombinant cDNA‐expressed human CYP enzymes in the presence of positive inhibitory controls. Metabolite formation was determined by validated LCMS/MS or HPLC methodologies. IC₅₀ inhibition constants were estimated from CYP activity inhibition plots using non‐linear regression. The most potent inhibition was shown for fennel towards CYP2D6 and 3A4 with respective IC₅₀ constants of 23 ± 2 and 40 ± 4 µg/ml, horsetail towards CYP1A2 with an IC₅₀ constant of 27 ± 1 µg/ml, and raspberry leaf towards CYP1A2, 2D6, and 3A4 with IC₅₀ constants of 44 ± 2, 47 ± 8, and 81 ± 11 µg/ml, respectively. Based on the recommended dosing of the different commercial herbal products, clinically relevant systemic CYP inhibitions could be possible for fennel, horsetail, and raspberry leaf. In addition, fennel and raspberry leaf might cause a clinically relevant inhibition of intestinal CYP3A4. The in vivo inhibitory potential of these herbs towards specific CYP enzymes should be further investigated. Copyright © 2013 John Wiley & Sons, Ltd.     

In vitro inhibition of CYP3A4 by herbal remedies frequently used by cancer patients

The herbal remedies Natto K2, Agaricus, mistletoe, noni juice, green tea and garlic, frequently used by cancer patients, were investigated for their in vitro inhibition potential of cytochrome P‐450 3A4 (CYP3A4) metabolism. To our knowledge, only garlic and green tea had available data on the possible inhibition of CYP3A4 metabolism. Metabolic studies were performed with human c‐DNA baculovirus expressed CYP3A4. Testosterone was used as a substrate and ketoconazole as a positive quantitative inhibition control. The formation of 6‐β‐OH‐testosterone was quantified by a validated HPLC methodology. Green tea was the most potent inhibitor of CYP3A4 metabolism (IC₅₀: 73 µg/mL), followed by Agaricus, mistletoe and noni juice (1324, 3594, >10 000 µg/mL, respectively). All IC₅₀ values were high compared with those determined for crude extracts of other herbal remedies. The IC₅₀/IC₂₅ ratios for the inhibiting herbal remedies ranged from 2.15 to 2.67, indicating similar inhibition profiles of the herbal inhibitors of CYP3A4. Garlic and Natto K2 were classified as non‐inhibitors. Although Agaricus, noni juice, mistletoe and green tea inhibited CYP3A4 metabolism in vitro, clinically relevant systemic or intestinal interactions with CYP3A4 were considered unlikely, except for a probable inhibition of intestinal CYP3A4 by the green tea product. Copyright © 2009 John Wiley & Sons, Ltd.     

Effect of Crude Extract of Eugenia jambolana Lam. on Human Cytochrome P450 Enzymes

The fruit of Eugenia jambolana Lam. is very popular for its anti‐diabetic property. Previous studies on the crude extract of E. jambolana (EJE) have successfully explored the scientific basis for some of its traditional medicinal uses. Considering its wide use and consumption as a seasonal fruit, the present study investigates the ability of E. jambolana to interact with cytochrome P450 enzymes. The standardized EJE was incubated with pooled human liver microsomes to assess the CYP2C9‐, CYP2D6‐, and CYP3A4‐mediated metabolism of diclofenac, dextromethorphan, and testosterone, respectively. The metabolites formed after the enzymatic reactions were quantified by high performance liquid chromatography. EJE showed differential effect on cytochrome P450 activities with an order of inhibitory potential as CYP2C9 > CYP3A4 > CYP2D6 having IC₅₀ of 76.69, 359.02, and 493.05 µg/mL, respectively. The selectivity of EJE for CYP2C9 rather than CYP3A4 and CYP2D6 led to perform the enzyme kinetics to explicate the mechanism underlying the inhibition of CYP2C9‐mediated diclofenac 4′‐hydroxylation. EJE was notably potent in inhibiting the reaction in a non‐competitive manner with K_i of 84.85 ± 5.27 µg/mL. The results revealed the CYP2C9 inhibitory potential of EJE with lower K_i value suggesting that EJE should be examined for its potential pharmacokinetic and pharmacodynamic interactions when concomitantly administered with other drugs. Copyright © 2014 John Wiley & Sons, Ltd.     

Evaluation of Inhibitory Effects of Caffeic acid and Quercetin on Human Liver Cytochrome P450 Activities

When herbal drugs and conventional allopathic drugs are used together, they can interact in our body which can lead to the potential for herb–drug interactions. This work was conducted to evaluate the herb–drug interaction potential of caffeic acid and quercetin mediated by cytochrome P450 (CYP) inhibition. Human liver microsomes (HLMs) were added to each selective probe substrates of cytochrome P450 enzymes with or without of caffeic acid and quercetin. IC₅₀, Ki values, and the types of inhibition were determined. Both caffeic acid and quercetin were potent competitive inhibitors of CYP1A2 (Ki = 1.16 and 0.93 μM, respectively) and CYP2C9 (Ki = 0.95 and 1.67 μM, respectively). Caffeic acid was a potent competitive inhibitor of CYP2D6 (Ki = 1.10 μM) and a weak inhibitor of CYP2C19 and CYP3A4 (IC₅₀ > 100 μM). Quercetin was a potent competitive inhibitor of CYP 2C19 and CYP3A4 (Ki = 1.74 and 4.12 μM, respectively) and a moderate competitive inhibitor of CYP2D6 (Ki = 18.72 μM). These findings might be helpful for safe and effective use of polyphenols in clinical practice. Our data indicated that it is necessary to study the in vivo interactions between drugs and pharmaceuticals with dietary polyphenols. Copyright © 2014 John Wiley & Sons, Ltd.     

In vitro modulatory effects on three major human cytochrome P450 enzymes by multiple active constituents and extracts of Centella asiatica

Ethnopharmacological relevance

Centella asiatica (CA) has been widely cultivated as a vegetable or spice in China, Southeast Asia, India, Sri Lanka, Africa, and Oceanic countries and traditionally used for wound healing and maintaining normal blood pressure.

Aim of the study

The present study was carried out to examine the potential modulatory effects of three commercially available active components (asiaticoside, asiatic acid and madecassic acid) and four extracts (aqueous, ethanol, dichloromethane and hexane) of CA on three major cDNA-expressed human cytochrome P450 (CYP) isoforms.

Materials and methods

High-performance liquid chromatography (HPLC)-based enzyme assays, namely tolbutamide 4-methyhydroxylase, dextromethorphan O-demethylase and testosterone 6β-hydroxylase assays were developed to probe activities of CYP2C9, CYP2D6 and CYP3A4, respectively. Probe substrates were incubated with or without each active component and extract for each isoform, followed by examination of the kinetics parameters, IC₅₀ and K_i, to characterize modulatory effects.

Results

CYP2C9 was more susceptible to inhibitory effects by CA extracts compared to CYP2D6 and CYP3A4. Moderate degree of inhibition was observed in ethanol (K_i = 39.1 μg/ml) and dichloromethane (K_i = 26.6 μg/ml) extracts implying potential risk of interaction when CYP2C9 substrates are consumed with CA products. The two extracts however showed negligible inhibition towards CYP2D6 and CYP3A4 (IC₅₀'s of 123.3 μg/ml and above). Similarly CA aqueous and hexane extracts did not significantly inhibit all three isoforms investigated (IC₅₀'s of 117.9 μg/ml and above). Among the active constituents investigated, asiatic acid and madecassic acid appeared to selectively inhibit CYP2C9 and CYP2D6 more than CYP3A4. Of particular interest is the potent inhibitory effect of asiatic acid on CYP2C9 (K_i = 9.1 μg/ml). This signifies potential risk of interaction when substrates for this isoform are taken together with CA products with high asiatic acid content. Inhibitions of asiatic acid with the other isoforms and that of madecassic acid with all isoforms were only moderate (K_i's ranged from 17.2 to 84.4 μg/ml). On the other hand, the IC₅₀ values for asiaticoside were high (1070.2 μg/ml or above) for all three isoforms, indicating negligible or low potential of this compound to modulate CYP enzymatic activity.

Conclusion

Centella asiatica extracts and active constituents inhibited CYP2C9, CYP2D6 and CYP3A4 activities with varying potency with CYP2C9 being the most susceptible isoform to inhibition. Significant inhibition was observed for asiatic acid and CA ethanol and dichloromethane extracts, implying involvement of semipolar constituents from CA in the effect. This study suggested that CA could cause drug–herb interactions through CYP2C9 inhibition.     

The in vitro inhibition of human CYP1A2, CYP2D6 and CYP3A4 by tetrahydropalmatine, neferine and berberine

The purpose of this study was to investigate the in vitro inhibition potential of the three purified herbal constituents tetrahydropalmatine (Tet), neferine (Nef) and berberine (Ber) towards recombinant human CYP1A2, CYP2D6 and CYP3A4 metabolic activities. In vitro incubations were performed with phenacetin, dextromethorphan and testosterone, respectively, as CYP substrates and their metabolites were determined by validated HPLC methods. Positive control inhibitors were run for each CYP in all incubation series. Inhibition was expressed by IC₅₀ values. All herbal constituents demonstrated some, but variable, inhibition potencies towards the investigated CYP enzymes. CYP2D6 was the most sensitive for inhibition and then mainly by Tet and Ber with IC₅₀ values of 3.04 ± 0.26 µm and 7.40 ± 0.36 µm , respectively. CYP3A4 and especially CYP1A2 were inhibited to a much smaller extent by all constituents. Neferine showed the lowest overall interaction potential towards the CYP enzymes investigated. The CYP inhibition potential for the purified constituents could be related to their chemical structures. No clinical significant metabolic interaction seems likely to occur between the CYP enzymes and herbal constituents tested, with a possible exception for the CYP2D6 inhibition by Tet and Ber. Copyright © 2011 John Wiley & Sons, Ltd.     

Inhibitory effects of cytochrome P450 enzymes CYP2C8, CYP2C9, CYP2C19 and CYP3A4 by Labisia pumila extracts

Ethnopharmacological relevance

Labisa pumila (LP), popularly known with its local name, Kacip Fatimah, is a well known herb grown in Indochina and Southeast Asia and is traditionally used to regain energy after giving birth in women. The propensity of LP to cause drug–herb interaction via cytochrome P450 (CYP) enzyme system has not been investigated.

Aim of the study

To evaluate the in vitro inhibitory effects of various LP extracts (aqueous, ethanol, dichloromethane (DCM) and hexane) on cytochrome P450 2C8 (CYP2C8), CYP2C9, CYP2C19 and CYP3A4 activities.

Materials and methods

Probe substrate-based high performance liquid chromatography (HPLC) methods were established for CYP2C9, CYP2C19 and CYP3A4 whereas a fluorescence-based enzyme assay was established for CYP2C8. The metabolite formations were examined after incubation of probe substrate with respective CYP isoform in the present or absent of LP extracts. The inhibitory effect of LP was characterized with kinetic parameters IC₅₀ and K_i values.

Results

LP extracts showed differential effect of CYP activities with the order of inhibitory potency as follows: dichloromethane>hexane>ethanol>aqueous. This differential effect was only observed in CYP2C isoforms but not CYP3A4. Both the hexane and DCM extracts exhibited moderate to potent inhibition towards CYP2C activities in different modes including non-competitive, competive and mixed-type. The DCM effect was notably strong for CYP2C8 and CYP2C9 showing K_i values of below 1 μg/ml. The selectivity of LP for CYP2C isoforms rather than CYP3A4 may be attributed to the presence of relatively small, lipophilic yet slightly polar compounds within the LP extracts.

Conclusions

The results of our study revealed that phytoconstituents contained in LP, particularly in hexane and dichloromethane extracts, were able to selectively inhibit CYP2C isoforms. The inactivation was characterized by low K_i values, in particular, in CYP2C8 and CYP2C9. These in vitro data indicate that LB preparations contain constituents that can potently inhibit CYP2C activities and suggest that this herb should be examined for potential pharmacokinetic drug interactions in vivo.     

A Comparative Study on the Inhibitory Effects of Different Parts and Chemical Constituents of Pomegranate on α‐Amylase and α‐Glucosidase

Pomegranate has been documented for the management of diabetes in Unani and Chinese medicine. This study compared the effects of the extracts of different pomegranate parts, including juice, peels, seeds and flowers, on carbohydrate digestive enzymes (α‐amylase and α‐glucosidase) in vitro. The methanolic flower extract inhibited α‐amylase and α‐glucosidase, while the methanolic peel extract inhibited α‐glucosidase selectively. The most active flower extract was subjected to water‐ethyl acetate partition. The ethyl acetate fraction was more potent than the water fraction in inhibiting both enzymes. Gallic acid and ellagic acid also showed selective inhibition against α‐glucosidase, and their presence in the ethyl acetate fraction was confirmed by HPLC‐DAD and HPLC‐HESI‐MS. Our findings suggest that the inhibition of carbohydrate digestive enzymes and their phenolic content may contribute to the anti‐hyperglycaemic effects of pomegranate flower and peel, and support their claims in diabetes. Copyright © 2012 John Wiley & Sons, Ltd.     

Aloe vera juice: IC₅₀ and dual mechanistic inhibition of CYP3A4 and CYP2D6

The aim of this study was to evaluate the inhibitory potency (IC₅₀ values) of ethanol extracts of two commercially available aloe vera juice (AVJ) products, on CYP3A4 and CYP2D6 activities in vitro and to determine if such inhibitions could be mechanism‐based. Recombinant human CYP3A4 and CYP2D6 enzymes were used and the activities were expressed by the metabolism of testosterone and dextromethorphan with ketoconazole and quinidine as positive inhibitor controls, respectively. The formed metabolites were quantified by validated HPLC techniques. Time‐ and NADPH‐ dependent inhibition assays were performed to evaluate a possible mechanism‐based inhibition. One of the AVJ extracts showed about twice the inhibitory potency towards both CYP enzymes over the other with IC₅₀ values of 8.35 ± 0.72 and 12.5 ± 2.1 mg/mL for CYP3A4 and CYP2D6, respectively. The AVJ was found to exert both CYP mediated and non‐CYP mediated inhibition of both CYP3A4 and CYP2D6. This dual mechanistic inhibition, however, seems to be governed by different mechanisms for CYP3A4 and CYP2D6. Estimated IC₅₀ inhibition values indicate no major interference of AVJ with drug metabolism in man, but the dual mechanistic inhibition of both enzymes might be of clinical significance. Copyright © 2011 John Wiley & Sons, Ltd.     

Studies on Bronchodilator Activity of Salvia officinalis (Sage): Possible Involvement of K+ Channel Activation and Phosphodiesterase Inhibition

The aqueous methanolic extract of the aerial parts of Salvia officinalis (So.Cr) was studied to provide possible underlying mechanism(s) for its medicinal use in asthma using the in vivo bronchodilatory assay and isolated tracheal preparations. S. officinalis (1–10 mg/kg) dose‐dependently inhibited carbachol (CCh)‐induced bronchospasm in anesthetized rats with three‐fold greater potency than the positive control, aminophylline. In tracheal preparations, So.Cr inhibited the low K⁺ (25 mM)‐induced contractions. Pretreatment of the tissues with 4‐aminopyridine reversed the inhibitory effect of the plant extract against low K⁺, whereas glibenclamide did not show any effect, thus showing the involvement of voltage‐sensitive K⁺ channels. When tested against the CCh‐induced pre‐contractions for the involvement of any additional mechanism, interestingly, the extract showed a dose‐dependent (0.03–0.1 mg/mL) inhibitory effect and shifted the inhibitory concentration response curves of isoprenaline to the left, thus showing phosphodiesterase enzyme inhibitory‐like action, similar to that of papaverine. These results indicate that the crude extract of S. officinalis possesses bronchodilatory activity mediated predominantly via activation of voltage‐dependent K⁺ channels and inhibition of phosphodiesterase enzyme; thus, this study provides sound pharmacological basis for its medicinal use in hyperactive airways disorders such as asthma and cough. Copyright © 2015 John Wiley & Sons, Ltd.     

Mechanism-based inhibition of CYP3A4 and CYP2D6 by Indonesian medicinal plants

Thirty samples of Indonesian medicinal plants were tested for their mechanism-based inhibition on cytochrome P450 3A4 (CYP3A4) and CYP2D6 via erythromycin N-demethylation and dextromethorphan O-demethylation activities in human liver microsomes. From screening with 0 and 20min preincubation at 0.5mg/ml of methanol extracts, five plants (Cinnamomum burmani bark, Foeniculum vulgare seed, Strychnos ligustrina wood, Tinospora crispa stem, and Zingiber cassumunar rhizome) showed more than 30% increase of CYP3A4 inhibition, while three (Alpinia galanga rhizome, Melaleuca leucadendron leaf, and Piper nigrum fruit) showed more than 30% increase of CYP2D6 inhibition. In these eight plants, Foeniculum vulgare seed, Cinnamomum burmani bark, and Strychnos ligustrina wood showed time-dependent inhibition on CYP3A4 and Piper nigrum fruit and Melaleuca leucadendron leaf on CYP2D6. Among these, four plants other than Melaleuca leucadendron revealed NADPH-dependent inhibition. Thus, Foeniculum vulgare, Cinnamomum burmani, and Strychnos ligustrina should contain mechanism-based inhibitors on CYP3A4 and Piper nigrum contain that on CYP2D6.     

In vitro inhibition of Huanglian [Rhizoma coptidis (L.)] and its six active alkaloids on six cytochrome P450 isoforms in human liver microsomes

Huanglian (Rhizoma Coptidis) as a popular herb has been used for the treatment of various diseases such as diarrhea, eye inflammation and women's abdominal ailments. Alkaloids are considered to be responsible for its pharmacological effects. In this investigation, Huanglian and its six alkaloids (coptisine, epiberberine, berberine, jateorrhizine, palmatine and magnoflorine) were systematically evaluated for their inhibition of six cytochrome P450 isoforms (CYP1A2, CYP2C8, CYP2C9, CYP2C19, CYP2D6 and CYP3A4) in human liver microsomes by the LC‐MS/MS method. Huanglian showed the strongest inhibition of CYP2D6, followed by CYP1A2 and CYP3A4_T. The IC₅₀ values were 5.8 µg/mL, 36.8 µg/mL and 59.2 µg/mL, respectively. Of the constituents tested, coptisine and epiberberine showed strong inhibition of CYP2D6 with IC₅₀ values of 4.4 µm and 7.7 µm ; berberine, jateorrhizine and palmatine showed weak inhibition of CYP2D6 with IC₅₀ values of 45.5 µm , 49.4 µm and 92.6 µm , respectively; jateorrhizine showed moderate inhibition of CYP3A4_T with an IC₅₀ value of 13.3 µm ; coptisine showed weak inhibition of CYP1A2 with an IC₅₀ value of 37.3 µm . In addition, activation was observed in coptisine/CYP2C9 and palmatine/CYP2C9/CYP2C19. Other CYP450 isoforms were not affected markedly by the six alkaloids. In conclusion, Huanglian showed in vitro inhibition of CYP2D6, the inhibition might be contributed mostly by protoberberine alkaloids, especially coptisine and epiberberine. Herb–drug interactions may occur through the CYP2D6 inhibition. Copyright © 2011 John Wiley & Sons, Ltd.     

Identification of cytochrome P450 (CYP) isoforms involved in the metabolism of corynoline,and assessment of its herb–drug interactions

Corynoline, an isoquinoline alkaloid isolated from the genus Corydalis, has been demonstrated to show multiple pharmacological effects including inhibition of acetylcholinesterase, inhibition of cell adhesion, fungitoxic and cytotoxic activity. The present study focused on its metabolism and metabolism‐based herb–drug interactions. After corynoline was incubated with human liver microsomes (HLMs) in the presence of NADPH, two metabolites (M‐1 and M‐2) were formed. Chemical inhibition experiments and assays with recombinant CYP isoforms showed that CYP2C9 was mainly involved in the formation of M‐1 and CYP3A4 mainly catalysed the production of M‐2. Among seven major CYP isoforms tested, corynoline showed strong inhibitory effects on the activities of CYP3A4 and CYP2C9, with an IC₅₀ of 3.3 ± 0.9 µm and 31.5 ± 0.5 µm , respectively. Kinetic analysis showed that inhibition of CYP3A4 by corynoline was best fit to a noncompetitive manner with K_i of 3.2 µm , while inhibition of CYP2C9 by corynoline was best fit to a competitive manner with K_i of 6.3 µm . Additionally, corynoline exhibited time‐dependent inhibition (TDI) toward CYP3A4. The inactivation kinetic parameters (K_I and k_inact) were calculated to be 6.8 µm and 0.07 min^‐1, respectively. These data are of significance for the application of corynoline and corynoline‐containing herbs. Copyright © 2010 John Wiley & Sons, Ltd.     

Marsdenia tenacissima extract inhibits gefitinib metabolism in vitro by interfering with human hepatic CYP3A4 and CYP2D6 enzymes

Ethnopharmacological relevance

The stem of Marsdenia tenacissima (Roxb.) Wight et Arn. is mainly produced in Yunnan China and has long been used as a medicine to treat cancer in China. Xiao-Ai-Ping injection, the water-soluble part of the stem of Marsdenia tenacissima, is administrated as an anti-cancer agent in clinics for decades. Our previous study showed that Marsdenia tenacissima extract (MTE) restored gefitinib sensitivity in gefitinib-resistant non-small cell lung cancer (NSCLC) cells, but the mechanism involved is unknown. Gefitinib undergoes hepatic metabolism predominantly through human cytochrome P450 (CYP) 3A4 and CYP2D6 enzymes. This study aims to evaluate whether MTE interferes with gefitinib metabolism via human hepatic P450 enzymes.

Material and methods

A cocktail-substrate assay was used to test the effect of MTE on major CYP enzyme activities by incubation of pooled human liver microsomes with specific substrate probes of CYP1A2, CYP2C9, CYP2C19, CYP2D6, and CYP3A4 in the absence and presence of MTE. Recombinant human CYP450 enzymes were used to predict in vitro gefitinib metabolic clearance in the absence and presence of MTE. The metabolites of the substrate probes and gefitinib were detected by high-performance liquid chromatographic tandem mass spectrometry (HPLC-MS/MS). Human hepatoma HepG2 cells were used to investigate the effect of gefitinib alone or in combination with MTE on CYP3A4 and CYP2D6 mRNA and protein expression.

Results

The cocktail-substrate assay showed that MTE inhibited CYP450 activities in human liver microsomes with the inhibition rate of 3A4>2C9>2C19>1A2>2D6. The co-administration of MTE with gefitinib significantly decreased the in vitro intrinsic clearance (Cl_int) of gefitinib by 2.6 and 4.0-fold for CYP2D6 and CYP3A4, respectively, but did not affect other CYP450s. CYP2D6 and CYP3A4 mRNA and protein expression in human hepatoma HepG2 cells were greatly reduced in the combined gefitinib and MTE treatment.

Conclusion

We demonstrate that MTE inhibits gefitinib metabolism by interfering with CYP3A4 and CYP2D6. Meanwhile, MTE combined with gefitinib down-regulates the mRNA and protein expression of CYP3A4 and CYP2D6 in the HepG2 cells. Thus, these data suggest that MTE is a promising herbal medicine to enhance gefitinib efficacy through improving its metabolic stability.     

Effects of Panax notoginseng saponins on the activities of CYP1A2, CYP2C9, CYP2D6 and CYP3A4 in rats in vivo

The aim of this study was to assess the influence of the Panax notoginseng saponins (PNS) on the activities of the drug‐metabolizing enzymes cytochrome P450 (CYP450) 1A2, 2 C9, 2D6 and 3A4 in rats. The activities of CYP1A2, 2 C9, 2D6 and 3A4 were measured using specific probe drugs. After pretreatment for 1 week with PNS or physiological saline (control group), probe drugs caffeine (10 mg/kg; CYP1A2 activity), tolbutamide (15 mg/kg; CYP2C9 activity), metoprolol (20 mg/kg; CYP2D6 activity) and dapsone (10 mg/kg; CYP3A4 activity) were administered to rats by intraperitoneal injection. The blood was then collected at different times for ultra performance liquid chromatography/tandem mass spectrometry (UPLC‐MS/MS) analysis. The data showed that PNS exhibited an induction effect on CYP1A2 by decreasing caffeine C_max (36.3%, p < 0.01) and AUC_0‐∞ (22.77%, p < 0.05) and increasing CL/F (27.03%, p < 0.05) compared with those of the control group. Western blot analysis was used to detect the effect of PNS on the protein level of CYP1A2, and the results showed that PNS could upregulate the protein expression of CYP1A2. However, no significant changes in CYP2C9, 2D6 or 3A4 activities were observed. In conclusion, the results indicate that PNS could induce CYP1A2, which may affect the disposition of medicines primarily dependent on the CYP1A2 pathway. Our work may be the basis of related herb–drug interactions in the clinic. Copyright © 2011 John Wiley & Sons, Ltd.     

Effects of Salvia miltiorrhiza extract on the liver CYP3A activity in humans and rats

Salvia miltiorrhiza (Danshen) is a famous Traditional Chinese medicine used widely in the treatment of cardiovascular and cerebrovascular diseases. This study explored the effects of Danshen capsules commonly used in clinical practice on the liver CYP3A activity in humans and rats. The effects of Danshen extract on liver CYP3A activity were determined by metabolism of model substrates in vitro in human and rat liver microsomes and in the rat in vivo. HPLC was used to determine model substrates and metabolites. Danshen extract (50–2000 µg/mL) competitively inhibited human and rat liver microsomal CYP3A activity with inhibition constant (K_i) values of 51 and 65 µg/mL, respectively. In the rat, 14‐day Danshen extract treatment (100 mg/kg/day, i.p. or 200 mg/kg/day, p.o.) decreased midazolam clearance (11–14%), with a concomitant increase in area under the curve (AUC; 12–17%) and a decrease in the volume of distribution (11–15%). These studies demonstrated that Danshen extract affected the metabolism of CYP3A substrates through competitive inhibition in human and rat liver in vitro and had no enzyme inducing effects on rat CYP3A in vivo after chronic administration. Copyright © 2011 John Wiley & Sons, Ltd.     

Effects of Vernonia cinerea Compounds on Drug‐metabolizing Cytochrome P450s in Human Liver Microsomes

Vernonia cinerea has been widely used in traditional medicines for various diseases and shown to aid in smoking abstinence and has anticancer properties. V. cinerea bioactive compounds, including flavonoids and hirsutinolide‐type sesquiterpene lactones, have shown an inhibition effect on the nicotine‐metabolizing cytochrome P450 2A6 (CYP2A6) enzyme and hirsutinolides reported suppressing cancer growth. In this study, V. cinerea ethanol extract and its bioactive compounds, including four flavonoids and four hirsutinolides, were investigated for an inhibitory effect on human liver microsomal CYPs 1A2, 2A6, 2B6, 2C8, 2C9, 2C19, 2D6, 2E1, and 3A4 using cocktail inhibition assays combined with LC‐MS/MS analysis. Among tested flavonoids, chrysoeriol was more potent in inhibition on CYP2A6 and CYP1A2 than other liver CYPs, with better binding efficiency toward CYP2A6 than CYP1A2 (K_i values in competitive mode of 1.93 ± 0.05 versus 3.39 ± 0.21 μM, respectively). Hirsutinolides were prominent inhibitors of CYP2A6 and CYP2D6, with IC₅₀ values of 12–23 and 15–41 μM, respectively. These hirsutinolides demonstrated time‐dependent inhibition, an indication of mechanism‐based inactivation, toward CYP2A6. Quantitative prediction of microsomal metabolism of these flavonoids and hirsutinolides, including half‐lives and hepatic clearance rate, was examined. These findings may have implications for further in vivo studies of V. cinerea. Copyright © 2017 John Wiley & Sons, Ltd.     

Inhibitory Activities of Thai Medicinal Plants with Promising Activities Against Malaria and Cholangiocarcinoma on Human Cytochrome P450

Malaria and cholangiocarcinoma remain important public health problems in tropical countries including Southeast Asian nations. Newly developed chemotherapeutic and plant‐derived drugs are urgently required for the control of both diseases. The aim of the present study was to investigate the propensity to inhibit cytochrome P450‐mediated hepatic metabolism (CYP1A2, CYP2C19, CYP2D6 and CYP3A4) of the crude ethanolic extract of eight Thai medicinal plants with promising activities against malaria and cholangiocarcinoma, using human liver microsomes in vitro. Piper chaba Linn. (PC) and Atractylodes lancea (thung.) DC. (AL) exhibited the most potent inhibitory activities on CYP1A2‐mediated phenacetin O‐deethylation with mean IC₅₀ of 0.04 and 0.36 µg/mL, respectively. Plumbago indica Linn. (PI) and Dioscorea membranacea Pierre. (DM) potently inhibited CYP2C19‐mediated omeprazole 5‐hydroxylation (mean IC₅₀ 4.71 and 6.92 µg/mL, respectively). DM, Dracaena loureiri Gagnep. (DL) and PI showed the highest inhibitory activities on dextromethorphan O‐demethylation (mean IC₅₀ 2.93–9.57 µg/mL). PC, DM, DL and PI exhibited the most potent inhibitory activities on CYP3A4‐mediated nifedipine oxidation (mean IC₅₀ 1.54–6.43 µg/mL). Clinical relevance of the inhibitory potential of DM, PC and PI is of concern for the further development of these plants for the treatment of malaria and/or cholangiocarcinoma. Copyright © 2015 John Wiley & Sons, Ltd.     

In Vitro Inhibition of the Transcription Factor NF‐κB and Cyclooxygenase by Bamboo Extracts

Several bamboo species have been used in traditional medicine for the treatment of inflammatory conditions. The present study evaluates the in vitro anti‐inflammatory properties of the traditionally used bamboo species Phyllostachys nigra (Lodd.) Munro and Sasa veitchii (Carr.) Rehder to explore their future research opportunities and therapeutic potential as anti‐inflammatory agents. The extracts were evaluated for their potential inhibitory activity at the level of NF‐κB‐induced gene expression and suppression of cyclooxygenase (COX)‐1 and COX‐2 enzyme activities, representative pharmacological targets for the anti‐inflammatory action of glucocorticoids and non‐steroidal anti‐inflammatory drugs, respectively. The activity of P. nigra (Lodd.) Munro and S. veitchii (Carr.) Rehder was compared with bamboo species without traditional anti‐inflammatory indications. High‐performance liquid chromatography with diode‐array detection and liquid chromatography–tandem mass spectrometry analyses were performed to phytochemically characterize the extracts. P. nigra (Lodd.) Munro leaf extract potently inhibited NF‐κB‐induced gene expression, while S. veitchii (Carr.) Rehder leaf extract exerted a selective COX‐2 inhibition. The crude extracts consistently showed a more potent bioactivity than the solid phase extraction fractions. P. nigra (Lodd.) Munro and S. veitchii (Carr.) Rehder both exert anti‐inflammatory properties, but act via a different molecular mechanism. Copyright © 2013 John Wiley & Sons, Ltd.