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.     

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.     

In vitro modulatory effects of Andrographis paniculata, Centella asiatica and Orthosiphon stamineus on cytochrome P450 2C19 (CYP2C19)

Ethno pharmacological relevance

Andrographis paniculata (AP), Centella asiatica (CA) and Orthosiphon stamineus (OS) are three popular herbs traditionally used worldwide. AP is known for the treatment of infections and diabetes and CA is good for wound healing and healthy skin while OS is usually consumed as tea to treat kidney and urinary disorders. Interaction of these herbs with human cytochrome P450 2C19 (CYP2C19), a major hepatic CYP isoform involved in metabolism of many clinical drugs has not been investigated to date.

Aim of the study

In this study, the modulatory effects of various extracts and major active constituents of AP, CA and OS on CYP2C19 activities were evaluated.

Materials and methods

S-Mephenytoin, the CYP2C19 substrate probe, was incubated in the presence or absence of AP, CA and OS components. The changes in the rate of metabolite (hydroxymephenytoin) formation were subsequently determined by a high-performance liquid chromatography (HPLC)-based enzyme assay to characterize the modulatory effects.

Results

Among the herbal extracts studied, AP ethanol extract and CA dichloromethane extract exhibited mixed type inhibition towards CYP2C19 with K_i values of 67.1 and 16.4 μg/ml respectively; CA ethanol extract and OS petroleum ether extract competitively inhibited CYP2C19 activity (K_i = 39.6 and 41.5 μg/ml respectively). Eupatorin (a major active constituent of OS) was found to significantly inhibit CYP2C19 by mixed type inhibition (K_i = 7.1 μg/ml or 20.6 μM).

Conclusions

It was observed that AP, CA and OS inhibited CYP2C19 activity with varying potency. While weak inhibitory effect was observed with AP, moderate to strong inhibition was observed with CA dichloromethane extract and eupatorin, the major OS constituent. Therefore care should be taken when these CA and OS components are co-administered with CYP2C19 substrates (such as omeprazole, proguanil, barbiturates, citalopram, and diazepam).     

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.     

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 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.     

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 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.     

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.     

In vitro antiprotozoan activity and mechanisms of action of selected Ghanaian medicinal plants against Trypanosoma,Leishmania, and Plasmodium parasites

Trypanosomiasis, leishmaniasis, and malaria are protozoan infections of public health importance with thousands of new cases recorded annually. Control of these infection(s) with existing chemotherapy is limited by drug toxicity, lengthy parenteral treatment, affordability, and/or the emergence of resistant strains. Medicinal plants on the other hand are used in the treatment of various infectious diseases although their chemical properties are not fully evaluated. In this study, we screened 112 crude extracts from 72 selected Ghanaian medicinal plants for anti‐Trypanosoma, anti‐Leishmania, and anti‐Plasmodium activities in vitro and investigated their mechanisms of action. Twenty‐three extracts from 20 plants showed significant antiprotozoan activity against at least 1 of 3 protozoan parasites screened with IC₅₀ values less than 20 μg/ml. Eleven extracts showed high anti‐Trypanosoma activity with Bidens pilosa whole plant and Morinda lucida leaf extracts recording the highest activities. Their IC₅₀ (selectivity index [SI]) values were 5.51 μg/ml (35.00) and 5.96 μg/ml (13.09), respectively. Nine extracts had high anti‐Leishmania activity with Annona senegalensis and Cassia alata leaf extracts as the most active. Their IC₅₀ (SI) values were 10.8 μg/ml (1.50) and 10.1 μg/ml (0.37), respectively. Six extracts had high anti‐Plasmodium activity with the leaf and stem‐bark extracts of Terminalia ivorensis recording the highest activity. Their IC₅₀ (SI) values were 7.26 μg/ml (129.36) and 17.45 μg/ml (17.17), respectively. Only M. lucida at 25 μg/ml induced significant apoptosis‐like cell death in Trypanosoma parasites. Anti‐Leishmania active extracts induced varying morphological changes in Leishmania parasites such as multiple nuclei and/or kinetoplast, incomplete flagella division, or nuclear fragmentation. Active extracts may be potential sources for developing new chemotherapy against these infections.     

Cytochrome P450 inhibitory potential of Triphala--a Rasayana from Ayurveda

Ethnopharmacological relevance

‘Triphala’ is one of the age-old, most commonly used polyherbal preparation from Ayurveda as Rasayana drug.

Aim of the study

This study was aimed at evaluating the effect of ‘Triphala’ on drug modulating enzymes to assess its safety through its potential to interact with co-administered drugs.

Materials and methods

The cytochrome P450 inhibitory effect of ‘triphala’ formulation was investigated on rat liver microsomes using CYP450-CO complex assay and on individual isoform such as CYP3A4 and 2D6 using fluorescence screening. RP-HPLC method was developed to standardize ‘triphala’ and its individual components using gallic acid as analytical marker compound.

Results

RP-HPLC analysis demonstrated the presence of gallic acid (4.30 ± 2.09 mg/g) in the formulation. The formulation showed 23% inhibition of the rat liver microsomes through CYP450-CO complex assay which is comparatively less when compared with the individual components. Further, the effect of standardized formulation dissolved in ethanol showed CYP3A4 and CYP2D6 inhibitory activity at the IC₅₀ values of 119.65 ± 1.91 μg/ml and 105.03 ± 0.98 μg/ml respectively. Gallic acid was also found to inhibit both the isoforms at the IC₅₀ values of 87.24 ± 1.11 μg/ml and 92.03 ± 0.38 μg/ml respectively.

Conclusions

Various concentrations of the formulation and its individual components showed significantly less inhibitory activity (p < 0.001) on individual isoforms when compared with the positive control. Assessment on the in vitro effect of ‘triphala’ on drug modulating enzymes has important implications for predicting the likelihood of herb-drug interactions if these are administered concomitantly.     

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.     

In vitro xanthine oxidase inhibitory activity of the fractions of Erythrina stricta Roxb.

Aim of the study

To assay the in vitro xanthine oxidase inhibitory activity of the various fractions of the hydromethanolic extract of the leaves of Erythrina stricta and to determine its enzyme inhibition mechanism.

Materials and methods

Xanthine oxidase inhibitory activity was assayed spectrophotometrically under aerobic conditions and the degree of enzyme inhibition was determined by measuring the increase in absorbance at 295 nm associated with uric acid formation. Enzyme kinetics was carried out using Lineweaver-Burk plots using xanthine as the substrate.

Results

Among the fractions tested, the chloroform fraction exhibited highest potency (IC₅₀ 21.2 ± 1.6 μg/ml) followed by the pet–ether (IC₅₀ 30.2 ± 2.2 μg/ml), ethyl acetate (IC₅₀ 44.9 ± 1.4 μg/ml) and residual (IC₅₀ 100 ± 3.3 μg/ml) fractions. The IC₅₀ value of allopurinol used, as the standard was 6.1 ± 0.3 μg/ml. Enzyme inhibition mechanism indicated that the mode of inhibition was of a mixed type.

Conclusion

These results suggest that the use of Erythrina stricta for the treatment of gout could be attributed to its xanthine oxidase inhibitory activity.     

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 antiplasmodial activity of plants used in Benin in traditional medicine to treat malaria

Aim of the study

The aim of the study was to evaluate the in vitro antiplasmodial activity of crude extracts of 12 plant species traditionally used in Benin for the treatment of malaria in order to validate their use.

Materials and methods

For each species, dichloromethane, methanol and total aqueous extracts were tested. The antiplasmodial activity of extracts was evaluated using the measurement of the plasmodial lactate dehydrogenase activity on chloroquine-sensitive (3D7) and resistant (W2) strains of Plasmodium falciparum. The selectivity of the different extracts was evaluated using the MTT test on J774 macrophage-like murine cells and WI38 human normal fibroblasts.

Results

The best growth inhibition of both strains of Plasmodium falciparum was observed with the dichloromethane extracts of Acanthospermum hispidum DC. (Asteraceae) (IC₅₀ = 7.5 μg/ml on 3D7 and 4.8 μg/ml on W2), Keetia leucantha (K. Krause) Bridson (syn. Plectronia leucantha Krause) (Rubiaceae) leaves and twigs (IC₅₀ = 13.8 and 11.3 μg/ml on 3D7 and IC₅₀ = 26.5 and 15.8 μg/ml on W2, respectively), Carpolobia lutea G.Don. (Polygalaceae) (IC₅₀ = 19.4 μg/ml on 3D7 and 8.1 μg/ml on W2) and Strychnos spinosa Lam. (Loganiaceae) leaves (IC₅₀ = 15.6 μg/ml on 3D7 and 8.9 μg/ml on W2). All these extracts had a low cytotoxicity.

Conclusion

Our study gives some justifications for the traditional uses of some investigated plants.     

A chemically characterized ethanolic extract of Thai Perilla frutescens (L.) Britton fruits (nutlets) reduces oxidative stress and lipid peroxidation in human hepatoma (HuH7) cells

Perilla frutescens is cultivated in East Asian countries including Thailand, and the nutlets (single‐seeded fruits) are used as traditional and medicinal food. Perilla nutlets extracted by ethyl acetate (EA), 80% ethanol (Eth), and hot water (HW) sequentially were chemically characterized using high‐resolution accurate liquid chromatography‐mass spectrometry with the main compounds detected assigned as rosmarinic acid and derivatives of the flavones apigenin and luteolin, with the more diverse chemical composition observed with the Eth extract. All extracts showed dose‐dependent free‐radical scavenging activity, with the Eth extract the most potent (IC₅₀ = 3.43 mg/ml for ABTS^? scavenging and 0.27 mg/ml for DPPH^? scavenging). The Eth extract also inhibited AAPH‐induced hemolysis (IC₅₀ = 0.07 mg/ml) more potently than did the HW (IC₅₀ = 0.38 mg/ml) and EA extracts (IC₅₀ = 1.63 mg/ml). An MTT test revealed all the extracts were noncytotoxic at concentrations up to 200 μg/ml. Only the Eth and EA extracts showed protective effects against the generation of reactive oxygen species and lipid peroxidation in FeCl₃‐induced HuH7 cells in a dose‐dependent manner. Our findings suggest the Eth extract of Thai perilla nutlets, containing rosmarinic acid and flavones and their derivatives, may have potential to provide protection against oxidative stress in hepatic disorders.     

清开灵注射液及其主要成分黄芩苷和栀子苷对人肝微粒体CYP450酶6种亚型的体外抑制作用研究

 目的 研究清开灵注射液及其主要成分黄芩苷和栀子苷对人肝微粒体CYP1A2、CYP2C8、CYP2C9、CYP2C19、CYP2D6和CYP3A4的体外抑制作用。方法 采用液相色谱-串联质谱法（LC-MS/MS）同时测定对乙酰氨基酚、6α-羟基紫杉醇、4-羟基双氯芬酸、4-羟基美芬妥英、右啡烷、1-羟基咪达唑仑和6β-羟基睾酮,分别代表CYP1A2、CYP2C8、CYP2C9、CYP2C19、CYP2D6和CYP3A4的活性;清开灵注射液、黄芩苷、栀子苷和7种混合探针底物在人肝微粒体中共同孵育,并计算其IC₅₀值表示对CYP450酶的抑制程度。结果 在人肝微粒体体外孵育体系中,清开灵注射液对CYP1A2的IC₅₀值为0.6%,对其他亚型的IC₅₀值从1.1%到6.0%;黄芩苷和栀子苷对CYP450酶6种亚型的IC₅₀值均大于100 μmol·L-1。结论 在正常剂量下,清开灵注射液对人肝微粒体CYP1A2可能有抑制作用,对人肝微粒体CYP2C8、CYP2C9、CYP2C19、CYP2D6和CYP3A4无明显抑制作用;黄芩苷和栀子苷对CYP450酶6种亚型均无抑制作用。     

Screening of plants used in Danish folk medicine to treat depression and anxiety for affinity to the serotonin transporter and inhibition of MAO-A

Ethnopharmacological relevance

A number of plant species are used in Danish folk medicine for treatment of depression and anxiety.

Materials and methods

Aqueous and ethanolic extracts of 17 plant species were tested for affinity to the serotonin transporter and for inhibition of MAO-A—both targets for antidepressive treatment.

Results

An ethanolic extract of aerial parts of Borago officinalis had affinity to the serotonin transporter. Ten extracts, from eight plants, had IC₅₀ values below 25 μg/ml extract in the MAO-A assay. The most active extracts in the MAO-A assay were the ethanol extract of seeds of Trigonella foenum-graecum (IC₅₀ 4 μg/ml); ethanol extract of leaves of Apium graveolens (IC₅₀ 5 μg/ml) and the water extract of aerial parts of Calluna vulgaris (IC₅₀ 8 μg/ml).

Conclusions

Besides Borago officinalis, which toxicity profile excludes it from further development as an herbal drug, none of the plants had potential as serotonin reuptake inhibitors. Several plants had MAO-A inhibitory activity.     

Antiplasmodial, anti-inflammatory and cytotoxic activities of various plant extracts from the Mascarene Archipelago

Aim of the study

Antiplasmodial activity, inhibition of nitric oxide (NO) overproduction, and anti-proliferative activity were investigated in vitro to evaluate the bioactive potential of the traditional pharmacopoeia of the Mascarene Archipelago, which is known for its biodiversity and for the richness of its endemic flora.

Materials and methods

A total of 45 methanol (MeOH) and dichloromethane (DCM) extracts were prepared from 19 plant species collected on Réunion and Mauritius Islands. Ninety-six-well microplate assays were performed on chloroquine sensitive Plasmodium falciparum 3D7 strain, on LPS-stimulated Raw 264.7 murine macrophages and on A-549, DLD-1 and WS1 human cells. Activity was evaluated through spectrophotometric methods.

Results

Activity was attributed to plant extracts expressing IC₅₀ < 50 μg/ml for antiplasmodial response, IC₅₀ < 100 μg/ml for cytotoxicity, and IC₅₀ < 130 μg/ml for anti-inflammatory reaction. The majority of the extracts tested (69%) exhibited potency in at least one of these three types of activity. This is the first report describing promising antiplasmodial activity (IC₅₀ < 15 μg/ml) for Psiadia dentata DCM extract and Terminalia bentzoe MeOH bark extract. NO inhibition assay revealed seven interesting plants, described for the first time as anti-inflammatory: Aphloia theiformis, Buddleja salviifolia, Eupatorium riparium, Hiptage benghalensis, Psiadia arguta, Psiadia dentata, and Scutia commersonii. Finally, anti-proliferative activity was observed for two endemic species, Geniostoma borbonicum and Nuxia verticillata.

Conclusion

Using the criterion of endemism as part of the criteria for traditional medicinal use raises the chances of finding original active principles. In our case, 86% of the endemic plants tested displayed pharmacological interest.     

The effects of commercial preparations of herbal supplements commonly used by women on the biotransformation of fluorogenic substrates by human cytochromes P450

The study set out to determine the potential for commercially available preparations of black cohosh (Actaea racemosa), chaste tree berry (Vitex agnus‐castus), crampbark (Viburnum opulus) and false unicorn (Chamaelirium luteum) to inhibit the major human drug metabolizing enzymes CYP1A2, CYP2C9, CYP2C19, CYP2D6 and CYP3A4 as well as CYP1A1 which activates some carcinogens. In vitro microplate‐based assays using cDNA‐expressed CYP450 isoforms and fluorogenic substrates were used. Components of the commercial herbal preparations interfered with the assays and limited the concentration ranges that could be tested. Nevertheless, the fluorogenic assays were robust, reproducible and easy to perform and thus are still useful for initial screening for potential herb – drug interactions. None of the preparations affected CYPs 1A1 or 2C9 at the concentrations tested but all preparations inhibited some of the enzymes with potencies around 1 μg/mL. The three most potent interactions were: chaste tree berry and CYP2C19 (IC₅₀ 0.22 μg/mL,); chaste tree berry and CYP3A4 (IC₅₀ 0.3 μg/mL); black cohosh and CYP2C19 (IC₅₀ 0.37 μg/mL,). Thus, the study successfully identified the potential for the commercial herbal preparations to inhibit human drug metabolizing enzymes. Whether this potential translates into clinically significant herb – drug interactions can only be confirmed by appropriate in vivo studies. Copyright © 2011 John Wiley & Sons, Ltd.