Physiologically Based Pharmacokinetic Modeling of Bergamottin and 6,7-Dihydroxybergamottin to Describe CYP3A4 Mediated Grapefruit-Drug Interactions

Grapefruit is a moderate to strong inactivator of CYP3A4, which metabolizes up to 50% of marketed drugs. The inhibitory effect is mainly attributed to furanocoumarins present in the fruit, irreversibly inhibiting preferably intestinal CYP3A4 as suicide inhibitors. Effects on CYP3A4 victim drugs can still be measured up to 24 hours after grapefruit juice (GFJ) consumption. The current study aimed to establish a physiologically-based pharmacokinetic (PBPK) grapefruit-drug interaction model by modeling the relevant CYP3A4 inhibiting ingredients of the fruit to simulate and predict the effect of GFJ consumption on plasma concentration-time profiles of various CYP3A4 victim drugs. The grapefruit model was developed in PK-Sim and coupled with previously developed PBPK models of CYP3A4 substrates that were publicly available and already evaluated for CYP3A4-mediated drug-drug interactions. Overall, 43 clinical studies were used for model development. Models of bergamottin (BGT) and 6,7-dihydroxybergamottin (DHB) as relevant active ingredients in GFJ were established. Both models include: (i) CYP3A4 inactivation informed by in vitro parameters, (ii) a CYP3A4 mediated clearance estimated during model development, as well as (iii) passive glomerular filtration. The final model successfully describes interactions of GFJ ingredients with 10 different CYP3A4 victim drugs, simulating the effect of the CYP3A4 inactivation on the victims' pharmacokinetics as well as their main metabolites. Furthermore, the model sufficiently captures the time-dependent effect of CYP3A4 inactivation as well as the effect of grapefruit ingestion on intestinal and hepatic CYP3A4 concentrations.

Imperatorin Influences Depressive-like Behaviors: A Preclinical Study on Behavioral and Neurochemical Sex Differences

Imperatorin, a naturally derived furanocoumarin, exerts promising neuropharmacological properties. Therefore, it might be applicable in the treatment of brain diseases such as depression. In the present project, we aimed to investigate the sex-dependent effects of imperatorin (1, 5, and 10 mg/kg) on behavior and neurochemistry associated with antidepressant effects. The depressive-like behaviors of male and female Swiss mice were investigated in a forced swim test (FST). Subsequently, High-Performance Liquid Chromatography (HPLC) was used to evaluate the level of serotonin, its metabolite, 5-HIAA, and noradrenaline, in mouse brains. The study revealed that only males responded to imperatorin (1 and 5 mg/kg) treatment and caused an antidepressant effect, such as with respect to depressive-like behaviors, lowering immobility time and increasing immobility latency. The HPLC analysis demonstrated that serotonin levels in the prefrontal cortex of females decreased with the middle dose of imperatorin (5 mg/kg), while in the male prefrontal cortex, the lower dose (1 mg/kg) boosted serotonin levels. There were no evident changes observed with respect to noradrenaline and serotonin metabolite levels in the male hippocampus. To conclude, we propose that imperatorin has antidepressant potential, seemingly only in males, influencing brain serotonin level, but the direct mechanism of action requires further investigation.

Study on pharmacokinetics of eight active compounds from Bufei-Huoxue Capsule based on UHPLC-MS/MS

Bufei-Huoxue Capsule (BFHX) was applied to treat chronic obstructive pulmonary disease (COPD) in China. It is composed of Astragali Radix, Paeoniae Radix Rubra, and Psoralea Fructus. A sensitive and reliable ultra-high-performance liquid chromatography-mass spectrometry (UHPLC-MS/MS) method was developed and validated to quantify the eight main bioactive compounds (psoralen, isopsoralen, neobabaisoflavone, corylin, bavachin, astragaloside IV, ononin and formononetin) in rat plasma after oral administration of BFHX. Osthol was used as an internal standard (IS). Plasma samples were pretreated with methanol to precipitate protein. Chromatographic separation was accomplished using Hypersil GOLD^TM C18 column (2.1 mm × 100 mm, 1.9 μm) with a gradient elution profile and a mobile phase consisting of (A) 0.1% formic acid in water and (B) acetonitrile and the flow rate was set at 0.2 mL/min. Multiple reaction monitoring (MRM) mode was applied to perform mass spectrometric analyses. All calibration curves were linear (r > 0.9908) in tested ranges. The intra- and inter-day accuracy and precisions of eight compounds at three different concentration levels were within the acceptable limits. The extraction recovery was within the range of 76.4 ∼ 105.2% and the matrix effects were within the range of 88.3 ∼ 115.0% (RSD ≤ 15.6%). The dilution effects were within the range of 90.2 ∼ 114.9%. These 8 compounds were stable under the tested conditions. So the developed method was valid to evaluate the pharmacokinetic study of eight bioactive compounds after oral administration of BFHX.

Imperatorin: A review of its pharmacology, toxicity and pharmacokinetics

As a naturally occurring furanocoumarin, the medicinal value of imperatorin has been studied more and more. We hope to provide useful information for the further development of imperatorin by analyzing the literature of imperatorin in recent years. By collating the literature on the pharmacology of imperatorin, we found that the pharmacological activity of imperatorin is wide and imperatorin can be used for anti-cancer, neuroprotection, anti-inflammatory, anti-hypertension and antibacterial. In addition, we found that some researchers confirmed the toxicity of imperatorin. Pharmacokinetic studies demonstrated that oxidation metabolism is the main metabolic pathways of imperatorin. At present, the shortcomings of research on imperatorin mainly include: most pharmacological studies are concentrated in vitro, lacking enough in vivo experimental data; more and more studies showed that imperatorin has synergistic effect with other drugs in anticancer and other aspects, but lacking the detailed explanation of the mechanism of the synergistic effect; imperatorin has side effect, but it lacks enough experimental conclusions. Based on the above defects, we believe that more in vivo experiments of imperatorin should be carried out in the future; future research need to explore synergistic mechanisms of imperatorin with other drugs, especially in anticancer; the dose affects both the pharmacological activity and the side effect of imperatorin. The relationship between the dose and the two aspects need to be further studied in order to reduce the side effect. In addition, through structural modification of imperatorin, it is possible to improve the treatment effect and reduce side effect.

Byakangelicin as a modulator for improved distribution and bioactivity of natural compounds and synthetic drugs in the brain

BACKGROUND

The elucidation of the biological roles of individual active compounds in terms of their in vivo bio-distribution and bioactivity could provide crucial information to understand how natural compounds work together as treatments for diseases.

PURPOSE

We examined the functional roles of Byakangelicin (Byn) to improve the brain accumulation of active compounds, e.g., umbelliferone (Umb), curcumin (Cur), and doxorubicin (Dox), and consequently to enhance their biological activities.

METHODS

Active compounds were administered intravenously to mice, with or without Byn, after which organs were isolated and visualized for their ex vivo fluorescence imaging to determine the bio-distribution of each active compound in vivo. For the in vivo bioactivity, Cur, either with or without Byn, was administered to a lipopolysaccharide (LPS)-induced neuro-inflammation model for 5 days, and its anti-inflammatory effects were examined by ELISA using a brain homogenate and serum.

RESULTS

We successfully demonstrated that the levels of active compounds (Umb, Cur, and Dox) in the brain, lung, and pancreas were greatly elevated by the addition of Byn via direct ex vivo fluorescence monitoring. In addition, sufficient accumulation of the active compound, Cur, greatly reduced LPS-induced neuro-inflammation in vivo.

CONCLUSION

Byn could serve as a modulator to allow improved brain accumulation of diverse active compounds (Umb, Cur, and Dox) and enhanced therapeutic effects.

[Determination and pharmacokinetics of main components for Psoralea corylifolia-Myristica fragrants drug pair by using UPLC-MS/MS]

To conduct multiple-reaction monitoring(MRM) quantitative analysis with ultra-high performance liquid chromatography coupled with mass spectrometry method(UPLC-MS/MS), determine the concentrations of psoralen, isopsoralen, bakuchiol and dehydrodiisoeugenol in plasma under positive iron mode with chloramghenicol as internal standard, and investigate the pharmacokinetics process of the main components before and after oral administration of drug pair Psoralea corylifolia -Myristica fragrants. Thirty-six SD rats were randomly divided into three group(A, B, C) and received P. corylifolia extract, P. corylifolia-M. fragrants extract, and M. fragrants extract respectively by intragastric administration. The plasma samples were collected at different time points. In the plasma samples, psoralen, isopsoralen, bakuchiol and dehydrodiisoeugenol showed good linear relationship within concentration rages of 0.098 125 to 39.25, 0.084 37 to 33.75, 0.046 875 to 18.75, and 0.11 to 2.2 mg•L⁻¹ respectively. The precision and stability results showed that the determination method of plasma concentration for such compositions was stable and reliable. The pharmacokinetic parameters obtained by DAS 2.0 showed varying differences before and after compatibility. According to the experimental results, the compatibility of P. corylifolia and M. fragrants can significantly impact the pharmacokinetic process of main components, expand their distribution and accelerate their metabolism and elimination in vivo.

A UPLC-MS/MS method for in vivo and in vitro pharmacokinetic studies of psoralenoside, isopsoralenoside, psoralen and isopsoralen from Psoralea corylifolia extract

ETHNOPHARMACOLOGICAL RELEVANCE

The dried fruit of Psoralea corylifolia L. has been used to prevent and treat vitiligo, osteoporosis, arthralgia and asthma in Traditional Chinese Medicine for some 1600 years. Psoralen (P), isopsoralen (IP), psoralenoside (PO) and isopsoralenoside (IPO) are the major coumarins and coumarin-related benzofuran glycosides in Psoraleae Fructus, which have been reported to show estrogen-like activity, osteoblastic proliferation accelerating activity, antitumor effects and antibacterial activity. The first aim of this study is to develop a rapid, sensitive and selective ultra performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) approach for simultaneous determination of PO, IPO, P and IP in rat plasma and samples collected from in vitro incubation experiments. The second aim is to investigate the pharmacokinetic properties of PO, IPO, P and IP after oral administration of Psoralea corylifolia extract (PCE) to rats. The third aim is to confirm the biotransformation of PO to P or IPO to IP under gastrointestinal conditions.

MATERIALS AND METHODS

A UPLC-MS/MS method with a C18 column and a mobile phase of methanol-0.1% aqueous formic acid was validated according to the criteria in FDA guidelines about bioanalytical method, which was developed to investigate the pharmacokinetic behavior of PO, IPO, P and IP from PCE and the metabolic pathways of PO to P or IPO to IP.

RESULTS

The criteria for establishment of a new UPLC-MS/MS method including selectivity, linearity, accuracy, precision, extraction recovery, matrix effect and stability were validated. This method was successfully applied to the quantitative determination of PO, IPO, P and IP in biological samples collected from both in vitro incubations and in vivo rat experiments. After oral administration of PCE to rat, pharmacokinetic parameters of these four compounds indicated that in vivo biotransformation may occur between PO and P or IPO and IP. Purified benzofuran glycosides fraction (PBGF), containing only PO and IPO, was orally administered to rats to further confirm the biotransformation of PO to P or IPO to IP under gastrointestinal conditions. An in vitro incubation study elucidated that PO and IPO were metabolized to P and IP by intestinal microflora through de-glucosylation.

CONCLUSIONS

This paper developed a rapid, sensitive and selective UPLC-MS/MS method for simultaneous determination of PO, IPO, P and IP from PCE in biological samples, and investigated on their comprehensive in vivo and in vitro pharmacokinetic studies. These obtained results showed that the metabolism by intestinal bacteria plays an important role in pharmacological effects of orally administered PCE.

The pharmacokinetics and oral bioavailability studies of columbianetin in rats after oral and intravenous administration

ETHNOPHARMACOLOGICAL RELEVANCE

The roots of Angelica pubescens Maxim. f. biserrata Shan et Yuan (RAP) has been used as Traditional Chinese medicine to treat rheumatic disease in China since ancient times, but its action mechanisms was not well understood. Columbianetin is one of the main active constituents isolated from RAP, which has been shown to have various biological activities, but the absorption characteristics and oral bioavailability dose proportionality of columbianetin in vivo were not studied.

MATERIALS AND METHODS

Male Sprague Dawley rats (210-230 g) received either an intravenous (i.v. 5, 10 and 20 mg kg(-1)) or oral (5, 10 and 20 mg kg(-1)) dose of columbianetin. The levels of columbianetin in plasma were measured by a simple and sensitive reversed-phase high-performance liquid chromatography (HPLC) method. The simple liquid-liquid extraction with ethyl acetate was used for sample preparation. Osthole was selected as internal standard (IS).

RESULTS

The chromatographic separation was accomplished on a C18 column at a flow rate of 1 mL min(-1), where water-methanol was used as mobile phase. The calibration curve of the method was linear in the concentration range of 0.05-2000 μg mL(-1). The intra and inter-day accuracy for columbianetin in rat plasma samples were within 8% and the variation was less than 8.3%. This method was suitable for the determination and pharmacokinetic study of columbianetin in rat plasma after both intravenous and oral administration. The results indicated that maximum plasma concentrations(Cmax) for the columbianetin (17-42 μg mL(-1)) were achieved at 0.3-0.5h post-oral dosing and the apparent volume of distribution (V/F) ranged from 0.38 to 0.44 L. Absolute bioavailability of columbianetin was assessed to be 81.13 ± 45.85, 81.09 ± 33.63 and 54.30 ± 23.19%, respectively. Terminal elimination half-life (T1/2) of the columbianetin after oral dosing was 60-90 min and were 2.5-3.3 fold longer than those observed for the i.v. dosing.

CONCLUSIONS

The pharmacokinetic properties of columbianetin in rat after oral administration were characterized as rapid oral absorption, quick clearance and good absolute bioavailability. The bioavailability of columbianetin ranged from 54 to 81% for 5, 10 and 20 mg kg(-1) oral doses. The bioavailability of columbianetin is independent of the doses studied. Columbianetin showed dose proportionality over the dose range 5-20 mg kg(-1). The results clearly demonstrated that columbianetin was one of the material bases of RAP. Furthermore, an HPLC method was demonstrated in this study for the research of traditional Chinese medicine.

[Study on tissue distribution of psoraleae fructus decoction in rats]

Advanced technologies are used to clarify the meridian tropism theory of traditional Chinese medicine is an important part of theoretical studies of traditional Chinese medicine. In this article, modern pharmacokinetic method was used to investigate tissue distribution characteristics of psoralen and isopsoralen of Psoraleae Fructus decoction in rats, in order to provide research ideas and experimental basis for the meridian tropism theory. In this study, various tissue samples such as heart, liver, spleen, lung, kidney, brain and spermary were collected at different times after oral administration with FP decoction, in order to determine concentration of psoralen and isopsoralen by HPLC. Pharmacokinetic parameters were calculated by DAS 2.0 software. The study results showed that HPLC indexes of psoralen and isopsoralen in various tissues of rats met the determination requirements of biological samples. Both components were distributed in all of the tissues, with AUC(0-t) order of liver > lung approximately kidney > heart > brain approximately spleen > spermary. There was significant difference between liver, kidney, lung and other tissues (P < 0.05). MRT(0-t) of both psoralen and isopsoralen were about 10 h. Therefore, psoralen and isopsoralen showed stronger targeting selection in liver, kidney and lung.

[Comparative study of absorption kinetics in intestines of rats on Xianlinggubao capsule prepared by different technologies]

OBJECTIVE

To study the characteristics of intestinal absorption of psoralen and isopsoralen of Xianlinggubao capsule, and compare the absorption of Xianlinggubao capsule prepared by different technologies.

METHOD

Non everted gut sac method was applied to investigate the influence of absorption sites and drug concentration on psoralen and isopsoralen absorption, which were determined by HPLC.

RESULT

Although the absorption rate constants of psoralen and isopsoralen in duodenum were more than that in jejunum and ileum, there was no significance difference between them. The absorption rate constants of psoralen kept at the same level when the concentrations of drug solution were at middle and low level, while the absorption rate constant at high level was absolutely lower than them (P < 0.05). The results of isopsoralen were the same as psoralen's.

CONCLUSION

Intestinal absorption of psoralen and isopsoralen may be affected by the dissolution. The absorption rate constants of psoralen and isopsoralen in new Xianlinggubao capsules are higher. The absorptions of active components absorption has significant difference in different preparation processes of Xianlinggubao capsule.

White and colored grapefruit juice produce similar pharmacokinetic interactions

Colored (pink and red) grapefruit pulp contains lower amounts of the furanocoumarin derivatives that cause pharmacokinetic interactions than white grapefruit pulp. However, few studies have examined interactions with colored juice products. Therefore, we examined the potential interactions of both white and colored grapefruit products by measuring the concentrations of furanocoumarin derivatives and inhibition of the metabolizing cytochrome P450 (CYP) 3A enzymes, the target of the furanocoumarins. We measured concentrations of three major furanocoumarin derivatives, bergaptol, bergamottin, and 6',7'-dihydroxybergamottin, with high-performance liquid chromatography in 21 brands of grapefruit juice sold in Japan, including 14 white and 7 colored brands. The mean difference in bergaptol, bergamottin, and 6',7'-dihydroxybergamottin concentrations in white grapefruit juice samples was 1.59, 0.902, and 1.03 times, respectively, the amounts in colored samples. White samples inhibited CYP3A-mediated testosterone-6beta oxidation in human liver microsomes by 1.04 and 0.922 times (whole juice and furanocoumarin, respectively) the inhibition by colored juice. Thus, colored grapefruit juice may produce drug interactions at the same rate as white grapefruit juice.

Drug interaction potentials among different brands of grapefruit juice

The discrepancy of drug-interaction potential among different brands of grapefruit juice was estimated based on inhibition of CYP3A activity caused by furanocoumarin derivatives in the grapefruit juice. Heat treatment of the grapefruit juice at 95 degrees C for 1 h was utilized to degrade the furanocoumarins. Initial velocity of testosterone 6beta-oxidation using human liver microsomes was determined as an indicator of the CYP3A activities. Changes in the velocities of the reaction mixture were observed when 10% of each brand of untreated grapefruit juice or heat-treated grapefruit juice was added. The differences in the velocities between untreated and heat-treated grapefruit juice were defined as the potentials of furanocoumarin-caused CYP3A-inhibitions.

[In situ rats single pass perfusion intestinal absorption of the effectivein components in Radix Angelicae Pubescentis]

In order to study the intestinal absorption behaviors of three active constituents, columbianetin acetate, osthole and columbianadin in Radix Angelicae Pubescentis extracts, in situ rat single pass intestine perfusion (SPIP) was carried out by the perfusion solution of the extract I containing less than 10% total coumarins. The absorption of extract II containing more than 60% total coumarins was compared with that of extract I by rat colon SPIP to elucidate the influence on absorption of the different coumarin content extracts of the Chinese traditional medicine. The samples of the perfusion solution were collected in certain intervals. The concentrations of three active components in the perfusion samples were determined by HPLC method. The results demonstrated that the absorption rate constants (Ka) or apparent permeability coefficients (Papp) of columbianetin acetate, osthole and columbianadin from extract I had no significant difference among concentration ranges of 62-555 microg x mL(-1), 101-887 microg x mL(-1), 19-186 microg x mL(-1), respectively. The absorption quantity of three components was proportional to its concentration respectively and the saturate absorption phenomena were not observed. This suggested that the absorption of columbianetin acetate, osthole and columbianadin showed the passive diffusion process. Three components could be absorbed in whole intestinal sections. The Ka and Papp of three components all showed colon > duodenum > jejunum > ileum in four different regions of rat intestine. At colon, Ka and P app were significant different from the others. The Ka or Papp of three components from the extract I was significantly more than that of same components from extract II. The extract I redounded to increase the absorption of three active components.

Development and validation of a gas chromatography–mass spectrometry method for the determination of isoimperatorin in rat plasma and tissue: Application to the pharmacokinetic and tissue distribution study

Isoimperatorin is one of the major furanocoumarins isolated from the dried root of Angelica dahuricae Benth.et Hook. The aim of the present study is to develop a procedure based on gas chromatography-mass spectrometry (GC-MS) to describe the analysis of isoimperatorin in rat plasma and tissue. The method was set up and adapted for the analysis of small biological samples taken from rats. Biological samples were extracted by liquid-liquid extraction. Extracted compounds were acetic ether/light petroleum (1:2). They were separated by GC on a DB-5MS analytical column and determined by a quadrupole mass spectrometer detector operated under selected ion monitoring mode. Excellent linearity was found between 0.027-5.32 microg/mL (r >0.99) for plasma samples and 0.108-21.28 microg/g (r >0.99) for the tissue samples. The limit of detection (LOD) was 1.0 ng/mL or 1.0 ng/g (three times signal/noise ratio). Within- and between-day precisions expressed as the relative standard deviation (RSD) for the method were 2.81-5.22% and 4.72-6.52%, respectively. The method recoveries for all samples were >80%. The main pharmacokinetic parameters obtained were T(max)=(1.06+/-0.12)h, C(max)=(0.72+/-0.14) microg/mL, AUC=(2.11+/-0.29)h microg/mL and K(a)=(1.76+/-0.13)/h. The concentrations of isoimperatorin in rat liver, heart, cerebellum and cerebrum were higher than those in other organs. The results presented here clearly indicate that this proposed method could be applicable to investigate the pharmacokinetic and tissue distribution of isoimperatorin in rats after administration.

High-performance liquid chromatographic method for the determination and pharmacokinetic study of oxypeucedanin hydrate and byak-angelicin after oral administration of Angelica dahurica extracts in mongrel dog plasma

A high-performance liquid chromatographic method was developed and validated for the determination and pharmacokinetic study of oxypeucedanin hydrate and byak-angelicin after oral administration of Angelica dahurica extracts in mongrel dog plasma. The coumarin components and the internal standard isopsoralen were extracted from plasma samples with the mixture of tert-butyl methyl ether and n-hexane (4:1, v/v). Chromatographic separation was performed on a C(18) column (200 mm x 4.6mm, 5 microm) with the mobile phase acetonitrile-methanol-water-acetic acid (20:15:65:2, v/v/v/v) at a flow-rate of 1.0 ml/min. Only the peak of oxypeucedanin hydrate and byak-angelicin could be detected in dog plasma after oral administration of ethanol extracts of A. dahurica mainly containing xanthotoxol, osthenol, imperatorin, oxypeucedanin hydrate and byak-angelicin. The calibration curves of oxypeucedanin hydrate and byak-angelicin were linear over a range of 22.08-8830.00 and 6.08-2430.00 ng/ml in dog plasma, respectively. The quantification limit of oxypeucedanin hydrate and byak-angelicin in dog plasma was 22.08 and 6.08 ng/ml, respectively. The intra- and inter-day precision was less than 7.6% and 8.5% and the accuracy was from 91.9% to 106.1%. The lowest absolute recoveries of oxypeucedanin hydrate and byak-angelicin were 85.7% and 87.0%, respectively. The method was successfully applied to the pharmacokinetic studies of oxypeucedanin hydrate and byak-angelicin in dog plasma after oral administration of ethanol extracts from A. dahurica.

Parsnip webworms and host plants at home and abroad: trophic complexity in a geographic mosaic

Due to differences in the structure of communities in which interactions are embedded, the intensity of interactions between species may vary with location; thus, what results from differences in outcomes and in degree of specialization is a geographic mosaic, which provides the raw material for divergent coevolutionary trajectories. Where selection intensity is great, reciprocal responses are likely in so-called "hotspots"; in contrast, where selection pressures are relaxed, reciprocal responses in "coldspots" are far less likely to occur. There are few if any studies examining how a gradient of increasing trophic complexity might influence the probability of phenotype matching and, correspondingly, the "temperature" of the coevolutionary interaction. This study was conducted to compare outcomes of the interaction between wild parsnip (Pastinaca sativa) and parsnip webworm (Depressaria pastinacella) in its indigenous area, Europe, to its area of introduction, the midwestern United States. Specifically, we tested the hypothesis that increasing trophic complexity, represented by alternate host plants or the presence of natural enemies, reduces the selective impact of parsnip webworms and hence diminishes linkage between host plant chemistry and webworms that would be expected in coevolutionary hotspots. This comparison of a two-species interaction in its area of introduction and its area of indigeneity revealed common patterns that are more reflective of interaction temperature than of continental origin. Where webworms are rare, parsnips produce lower levels of xanthotoxin and bergapten in both the midwestern United States and Netherlands populations. However, the most striking result from this intercontinental comparison is that what is a ubiquitous two-species interaction in North America is in fact exceptional in Europe; webworms could more reliably be found infesting H. sphondylium even where P. sativa was available as well. This preference for H. sphondylium exists despite the comparatively high probability of parasitism associated with this host plant and may reflect the overall lower furanocoumarin content of H. sphondylium. The interaction of parsnip webworms and wild parsnips at home and away demonstrates clearly the potential for rapid contemporary evolution of chemical traits upon re-association with a coevolved enemy, a potential evolutionary outcome that should be considered in the design and implementation of future weed biological control programs.

Naringin is a major and selective clinical inhibitor of organic anion-transporting polypeptide 1A2 (OATP1A2) in grapefruit juice

We showed previously that grapefruit and orange juices inhibited human enteric organic anion-transporting polypeptide (OATP)1A2 in vitro and lowered oral fexofenadine bioavailability clinically. Inhibition of OATP1A2 transport by flavonoids in grapefruit (naringin) and orange (hesperidin) was conducted in vitro. Two randomized, crossover, pharmacokinetic studies were performed clinically. In one study, 120 mg of fexofenadine was ingested with 300 ml grapefruit juice, an aqueous solution of naringin at the same juice concentration (1,200 microM), or water. In the other study, fexofenadine was administered with grapefruit juice, with or 2 h before aqueous suspension of the particulate fraction of juice containing known clinical inhibitors of enteric CYP3A4, but relatively low naringin concentration (34 microM), or with water. Naringin and hesperidin's half-maximal inhibitions were 3.6 and 2.7 microM, respectively. Fexofenadine area under the plasma drug concentration-time curves (AUCs) with grapefruit juice and naringin solution were 55% (P<0.001) and 75% (P<0.05) of that with water, respectively. Fexofenadine AUCs with grapefruit juice and particulate fractions were 57% (P<0.001), 96% (not significant (NS)), and 97% (NS) of that with water, respectively. Individuals tested in both studies (n=9 of 12) had highly reproducible fexofenadine AUC with water (r(2)=0.85, P<0.001) and extent of reduction of it with grapefruit juice (r(2)=0.72, P<0.01). Naringin most probably directly inhibited enteric OATP1A2 to decrease oral fexofenadine bioavailability. Inactivation of enteric CYP3A4 was probably not involved. Naringin appears to have sufficient safety, specificity, and sensitivity to be a clinical OATP1A2 inhibitor probe. Inherent OATP1A2 activity may be influenced by genetic factors. This appears to be the first report of a single dietary constituent clinically modulating drug transport.

Targeting effector memory T cells with the small molecule Kv1.3 blocker PAP-1 suppresses allergic contact dermatitis

The voltage-gated potassium channel Kv1.3 has been recently identified as a molecular target that allows for selective pharmacological suppression of effector memory T (T(EM)) cells without affecting the function of naïve and central memory T cells. We here investigated whether PAP-1, a small molecule Kv1.3 blocker (EC50=2 nM), could suppress allergic contact dermatitis (ACD). In a rat model of ACD, we first confirmed that the infiltrating cells in the elicitation phase are indeed CD8+ CD45RC- memory T cells with high Kv1.3 expression. In accordance with its selective effect on T(EM) cells, PAP-1 did not impair sensitization, but potently suppressed oxazolone-induced inflammation by inhibiting the infiltration of CD8+ T cells and reducing the production of the inflammatory cytokines IFN-gamma, IL-2, and IL-17 when administered intraperitoneally or orally during the elicitation phase. PAP-1 was equally effective when applied topically, demonstrating that it effectively penetrates skin. We further show that PAP-1 is not a sensitizer or an irritant and exhibits no toxicity in a 28-day toxicity study. Based on these results we propose that PAP-1 could potentially be developed into a drug for the topical treatment of inflammatory skin diseases such as psoriasis.

Understanding the grapefruit-drug interaction

The inhibitory interaction of grapefruit juice and CYP3A4 medication metabolism was discovered in 1989. CYP3A4 enzymes are responsible for the metabolism of more than 60% of orally-administered drugs. Grapefruit components inhibit CYP3A4 drug oxidation and P-glycoprotein transportation, allowing more systemic drug bioavailability. This inhibitory interaction should be kept in mind when prescribing drugs that are metabolized by CYP3A4, such as orally administered midazolam, triazolam, and diazepam.

Two Major Grapefruit Juice Components Differ in Time to Onset of Intestinal CYP3A4 Inhibition

Grapefruit juice elevates blood levels of some drugs taken orally, primarily by inhibiting intestinal CYP3A4-mediated first-pass metabolism. Two prominent furanocoumarins in the juice, 6',7'-dihydroxybergamottin (DHB) and bergamottin (BG), have been demonstrated as important contributors to grapefruit juice-drug interactions. Using CYP3A4-expressing Caco-2 cells and representative probes from distinct CYP3A4 substrate subgroups (midazolam, testosterone), we compared the time-dependent inhibitory properties of DHB and BG. DHB rapidly inhibited CYP3A4 activity in a substrate-independent fashion with maximal inhibition (>/=85%) generally occurring within 30 min. In contrast, BG had a slower onset and exhibited substrate-dependent inhibition. Whereas testosterone 6beta-hydroxylation was inhibited by >50% with all exposure times (0.5-3 h), midazolam 1'-hydroxylation was unaffected, or even activated, with short exposure times (<1 h). After a 3-h exposure, however, BG had begun to "catch up" with DHB, causing >/=70% inhibition, independent of substrate. Likewise, loss of CYP3A4 protein, believed to reflect rapid intracellular degradation of the enzyme following mechanism-based inactivation, was comparable between the furanocoumarins (40-50%). The time course of BG-mediated inhibition was similar after just a 30-min exposure, indicating that the short exposure presumed to occur after juice ingestion is sufficient to initiate the events required to cause substantial inhibition (>/=50%). These results suggest that after ingestion of a glass of grapefruit juice, CYP3A4 is maximally inhibited by DHB before BG has the opportunity to act. However, foods containing BG but not DHB (e.g., lime juice) could produce a substrate-dependent interaction with drugs consumed concomitantly, but a substrate-independent interaction with drugs taken several hours after food consumption.

Disposition of 4,6,4'-trimethylangelicin in mice maintained in the dark and after UVA irradiation

The disposition of the furocoumarin 4,6,4'-trimethylangelicin (4,6,4'-TMA) was studied in mice. After oral administration of (3)H 4,6,4'-TMA, radioactivity measured in serum shows fast absorption and slow elimination. Serum protein binding is higher as compared to 8-methoxypsoralen (8-MOP), currently used in photochemotherapy (PUVA) and linearly declines from 30 min to 6 h after administration. Distribution in the various organs was similar to that of 8-MOP and was relatively uninfluenced by UVA radiation, required for the biological effects of 4,6,4'-TMA. Mice eliminate (3)H 4,6,4'-TMA mostly through the urine, but also through the faeces. Two metabolites were identified in the urine and serum of the treated mice, one of which proved to be a derivative of 4,6,4'-TMA, formed by hydrogenation of the double 4',5' bond of the furocoumarin nucleus.

6'7'-Dihydroxybergamottin contributes to the grapefruit juice effect

OBJECTIVE

Our objective was to assess the contribution of 6',7'-dihydroxybergamottin (DHB) to the inhibitory effect of grapefruit juice toward intestinal cytochrome P450 (CYP) 3A4.

METHODS

An aqueous extract was prepared from grapefruit juice by centrifugation, filtration, and repeated washing of the particulate with water. The concentrations of various furanocoumarins in this grapefruit juice "serum" and in whole grapefruit juice were measured by HPLC and their identities confirmed by liquid chromatography-tandem mass spectrometry. Five healthy volunteers were given a single tablet of felodipine (10 mg) with whole grapefruit juice, orange juice-containing serum, or plain orange juice (control). The pharmacokinetic outcomes of felodipine were evaluated by noncompartmental methods. The effects of serum and purified DHB (at the same concentrations as those measured in the orange juice-containing serum used in the clinical study) were compared, in vitro, with regard to (1) the reversible and mechanism-based inhibition of the catalytic activity of complementary deoxyribonucleic acid-expressed CYP3A4 and (2) the time-dependent loss of immunoreactive CYP3A4 protein in modified Caco-2 cells.

RESULTS

The concentration of DHB in serum was comparable to that measured in whole grapefruit juice (38 micromol/L versus 43 micromol/L), and the concentrations of other known furanocoumarins were well below the lowest published concentration required to inhibit catalytic activity by 50%. Relative to plain orange juice, orange juice-containing serum significantly increased the median felodipine area under the plasma concentration-time curve by 1.9-fold (P =.04) and increased the maximum concentration by 1.7-fold (P =.01). In vitro, serum and purified DHB had similar inhibitory effects toward CYP3A4 activity with respect to both reversible inhibition (95% confidence interval, 85% +/- 5.7% and 75% +/- 4.5%, respectively) and mechanism-based inhibition after a 15-minute preincubation (95% confidence interval, 79% +/- 6.8% and 78% +/- 5.7%, respectively). In Caco-2 cells the time-averaged extents of CYP3A4 protein loss caused by serum and purified DHB were identical (43%).

CONCLUSION

The interaction between grapefruit juice serum and felodipine can be attributed largely to DHB. This establishes DHB as an important contributor to the grapefruit juice effect.

The effect of bergamottin on diazepam plasma levels and P450 enzymes in beagle dogs

Bergamottin, a furanocoumarin isolated from grapefruit juice, was investigated for the ability to increase diazepam bioavailability and for its effect on cytochrome P450 (P450) enzymes in the beagle dog liver and intestine. To study the effect of bergamottin on diazepam pharmacokinetics, male beagle dogs were dosed with bergamottin (1 mg/kg) p.o. 0 or 2 h before p.o. diazepam (10 mg). In a second experiment, bergamottin (0.1 mg/kg) was dosed i.v. or p.o. 1 h before p.o. diazepam (10 mg). Plasma samples were collected over 24 h postdose, analyzed by liquid chromatography/mass tandem spectrometry, and diazepam pharmacokinetic parameters were determined. To study the effect of bergamottin on P450 enzymes, beagle dog liver and jejunum was harvested after a 10-day dosing regimen of bergamottin (1 mg/kg) p.o. per day; microsomes were prepared and analyzed for CYP3A12, CYP2B11, CYP1A1/2, and tolbutamide hydroxylase activity. Bergamottin predosing increased the plasma levels of diazepam as observed by C(max) (278.75 ng/ml versus 5.49 ng/ml) and the area under the curve [AUC((0-TLDC))] (247.69 versus 2.79 ng x hr/ml) in bergamottin versus placebo groups, respectively, indicating P450 enzyme inhibition. Diazepam plasma concentrations were increased to a similar level in the presence of i.v. and p.o. administered bergamottin. In hepatic microsomes, bergamottin treatment for 10 days reduced the activity of CYP3A12 by 50% and CYP1A1/2 by 75%. Tolbutamide hydroxylase activity did not change, and CYP2B11 activity was moderately induced. In jejunal microsomes, CYP3A12 activity doubled with bergamottin treatment. CYP2B11, CYP1A1/2 activity and tolbutamide hydroxylation was not detected. In conclusion, bergamottin is both an inhibitor and an inducer of P450 enzymes.

Inhibition of rat brain monoamine oxidase activities by psoralen and isopsoralen: implications for the treatment of affective disorders

Psoralen and isopsoralen, furocoumarins isolated from the plant Psoralea corylifolia L., were demonstrated to exhibit in vitro inhibitory actions on monoamine oxidase (MAO) activities in rat brain mitochondria, preferentially inhibiting MAO-A activity over MAO-B activity. This inhibition of enzyme activities was found to be dose-dependent and reversible. For MAO-A, the IC50 values are 15.2 +/- 1.3 microM psoralen and 9.0 +/- 0.6 microM isopsoralen. For MAO-B, the IC50 values are 61.8 +/- 4.3 microM psoralen and 12.8 +/- 0.5 microM isopsoralen. Lineweaver-Burk transformation of the inhibition data indicates that inhibition by both psoralen and isopsoralen is non-competitive for MAO-A. The Ki values were calculated to be 14.0 microM for psoralen and 6.5 microM for isopsoralen. On the other hand, inhibition by both psoralen and isopsoralen is competitive for MAO-B. The Ki values were calculated to be 58.1 microM for psoralen and 10.8 microM for isopsoralen. These inhibitory actions of psoralen and isopsoralen on rat brain mitochondrial MAO activities are discussed in relation to their toxicities and their potential applications to treat affective disorders.

[A study on nasal absorption of psoralen and isopsoralen in Psoralea corylifolia L]

OBJECTIVE

To investigate the nasal absorption regularities of psoralen and isopsoralen of different concentrations.

METHOD

Building an experimental model of rat in situ nasal recirculation and determining the contents of psoralen and isopsoralen by HPLC.

RESULT

The nasal absorption of psoralen and isopsoralen fitted in with zero order kinetics, getting saturated with the increase of concentration.

CONCLUSION

A suitable concentration is necessary for the preparation of nasal remedies psoralen and isopsoralen.

Psoralens percutaneous permeation across the human whole skin and the epidermis in respect to their polarity (in vitro study)

8-methoxypsoralen (8-MOP), 5-methoxypsoralen (5-MOP) and 4,5',8-trimethylpsoralen (TMP) are commonly used in PUVA therapy [psoralen (P) + ultraviolet light A (UVA) irradiation] to treat skin diseases such as psoriasis and vitiligo. In order to predict the choice of the suitable drug(s) for topical applications, with appropriate dosage, percutaneous permeation of the psoralens, in connection with their solubilities and partition coefficients in an octanol/water system, were investigated. The percutaneous penetration experiments were accomplished by the deposit of ethanolic psoralen solution onto human skin and epidermis fragments mounted on Franz cells. Six cells were employed for each psoralen solution and for the whole skin layer as well as for the epidermis. The diffused psoralens in the receptor solution (1.4%, of human serum albumin) were quantified by using high performance liquid chromatography. The solubilities and the partition coefficients (PC) were carried out in an octanol/water system, in triplicate by using spectrofluorimetry. The results demonstrated that cumulated permeated quantities (ng/cm2) over 24 h, across the whole skin and the epidermis were in the following order for the three psoralens: 8-MOP > 5-MOP > TMP. The lipophilicity, expressed via the log PC, was as follows: 1.93 +/- 0.01 (8-MOP), 2.00 +/- 0.01 (5-MOP) and 3.14 +/- 0.01 (TMP). It was inversely correlated with cumulated penetrated amounts over 24 h in both whole skin and epidermis. From these results, TMP could be predicted as the most convenient psoralen for topical applications, because of its weak penetrability. Considering the relationship between psoralens lipophilicity and permeation, only 5-MOP and 8-MOP could be used, topically or orally, especially in the case of generalised skin disorders.

[The effect of furanocoumarins on microsomal oxidation in the rat liver]

Puvalen and psoberan are inhibitors of monoxygenase enzyme system activity of the liver. Puvalen exerts the biphase effect on the system, so it may be referred to such classic inhibitors as SKF-525A and pyperonil butoxide. Psoberan does not exert the biphase effect on the monoxygenase system that is apparently connected with its negative action on biomembrane structure of hepatocytes. The results must be taken into consideration when patients are treated with psoralens.

Biopharmaceutics, pharmacokinetics and pharmacology of psoralens

The psoralen derivative 8-methoxypsoralen (8-MOP) and to a lesser extent some other psoralens, including 5-methoxypsoralen (5-MOP) and 4,5',8-trimethylpsoralen (TMP) have acquired a place in the treatment of psoriasis and other dermatoses. They are only active when combined with long-wave ultraviolet light: PUVA therapy (Psoralen plus UVA). Successful PUVA therapy depends on sufficiently high psoralen concentrations coinciding with the time of irradiation. The use of oral or rectal pharmaceutical formulations with 8-MOP dissolved in liquid is preferable to conventional tablets or capsules. Since no formulation of 5-MOP with fast and predictable absorption is available 8-MOP should be preferred in PUVA therapy. The effectiveness of oral TMP is doubtful, because of low serum concentrations, probably due to malabsorption.

Psoralens and related compounds in the treatment of psoriasis

PUVA therapy has radically altered the management of severe psoriasis. It is of greatest benefit in those patients with extensive involvement, and in those unresponsive to conventional therapy. The long term side effects of PUVA currently limit its use to patients with disabling disease. The full extent of long term side effects has yet to be defined. In order to reduce the toxicity and improve the efficacy of PUVA, a better understanding of the molecular aspects of psoralen-DNA interaction, DNA repair, and mutagenesis is required. The action spectrum of PUVA in clearing psoriasis has yet to be defined. By limiting the spectrum of UVA exposure it may be possible to reduce some of the toxic effects of PUVA. The recent advances in the formulation of 8-MOP preparations has yielded a drug with more predictable pharmacokinetics and clinical response. Further research with newer psoralens may produce more effective and less toxic compounds. In the last ten years, PUVA has been both a valuable addition to dermatologists' clinical armamentarium and a useful tool in increasing our understanding of cellular biology and the interaction between ultraviolet radiation and biologic systems.