Effects of Chrysin and Chrysin-7-sulfate on Ochratoxin A-Albumin Interactions and on the Plasma and Kidney Levels of the Mycotoxin in Rats.

The nephrotoxic mycotoxin ochratoxin A (OTA) is a common food contaminant. OTA binds to the Sudlow's Site I region of serum albumin with very high affinity, resulting in its slow elimination. The displacement of OTA from albumin may be beneficial due to the faster excretion of the mycotoxin, while it may also lead to the increased tissue uptake of OTA. Furthermore, it is challenging to displace the mycotoxin from albumin even with high-affinity Site I ligands. In this study, we tested the impacts of Site I and Heme site ligands on OTA-albumin interactions by applying fluorescence spectroscopic, ultracentrifugation, and modeling studies. Chrysin-7-sulfate (C7S) strongly displaced OTA from both human and rat albumins; therefore, the impacts of C7S (single intravenous administration) and the parent flavonoid chrysin (repeated peroral treatment) were examined on the plasma and kidney levels of OTA in rats. Chrysin barely influenced the concentrations of mycotoxin in plasma and kidneys. In the first few hours, C7S significantly decreased the plasma levels of OTA compared to the control animals; while after 24 h, only minor differences were noticed. Our study highlights the superior displacing ability of C7S vs OTA regarding human and rat albumins.

Interaction of luteolin, naringenin, and their sulfate and glucuronide conjugates with human serum albumin, cytochrome P450 (CYP2C9, CYP2C19, and CYP3A4) enzymes and organic anion transporting polypeptide (OATP1B1 and OATP2B1) transporters.

Luteolin and naringenin are flavonoids found in various foods/beverages and present in certain dietary supplements. After a high intake of these flavonoids, their sulfate and glucuronide conjugates reach micromolar concentrations in the bloodstream. Some pharmacokinetic interactions of luteolin and naringenin have been investigated in previous studies; however, only limited data are available in regard to their metabolites. In this study, we aimed to investigate the interactions of the sulfate and glucuronic acid conjugates of luteolin and naringenin with human serum albumin, cytochrome P450 (CYP2C9, 2C19, and 3A4) enzymes, and organic anion transporting polypeptide (OATP1B1 and OATP2B1) transporters. Our main findings are as follows: (1) Sulfate conjugates formed more stable complexes with albumin than the parent flavonoids. (2) Luteolin and naringenin conjugates showed no or only weak inhibitory action on the CYP enzymes examined. (3) Certain conjugates of luteolin and naringenin are potent inhibitors of OATP1B1 and/or OATP2B1 enzymes. (4) Conjugated metabolites of luteolin and naringenin may play an important role in the pharmacokinetic interactions of these flavonoids.

Testing Serum Albumins and Cyclodextrins as Potential Binders of the Mycotoxin Metabolites Alternariol-3-Sulfate, Alternariol-9-Monomethylether and Alternariol-9-Monomethylether-3-Sulfate.

Alternaria mycotoxins, including alternariol (AOH), alternariol-9-monomethylether (AME), and their masked/modified derivatives (e.g., sulfates or glycosides), are common food contaminants. Their acute toxicity is relatively low, while chronic exposure can lead to the development of adverse health effects. Masked/modified metabolites can probably release the more toxic parent mycotoxin due to their enzymatic hydrolysis in the intestines. Previously, we demonstrated the complex formation of AOH with serum albumins and cyclodextrins; these interactions were successfully applied for the extraction of AOH from aqueous matrices (including beverages). Therefore, in this study, the interactions of AME, alternariol-3-sulfate (AS), and alternariol-9-monomethylether-3-sulfate (AMS) were investigated with albumins (human, bovine, porcine, and rat) and with cyclodextrins (sulfobutylether-ß-cyclodextrin, sugammadex, and cyclodextrin bead polymers). Our major results/conclusions are the following: (1) The stability of mycotoxin-albumin complexes showed only minor species dependent variations. (2) AS and AMS formed highly stable complexes with albumins in a wide pH range, while AME-albumin interactions preferred alkaline conditions. (3) AME formed more stable complexes with the cyclodextrins examined than AS and AMS. (4) Beta-cyclodextrin bead polymer proved to be highly suitable for the extraction of AME, AS, and AMS from aqueous solution. (5) Albumins and cyclodextrins are promising binders of the mycotoxins tested.

Testing the Protective Effects of Sulfobutylether-Βeta-Cyclodextrin (SBECD) and Sugammadex against Chlorpromazine-Induced Acute Toxicity in SH-SY5Y Cell Line and in NMRI Mice.

Chlorpromazine (CPZ) is an antipsychotic drug which can cause several adverse effects and drug poisoning. Recent studies demonstrated that CPZ forms highly stable complexes with certain cyclodextrins (CDs) such as sulfobutylether-ß-CD (SBECD) and sugammadex (SGD). Since there is no available antidote in CPZ intoxication, and considering the good tolerability of these CDs even if when administered parenterally, we aimed to investigate the protective effects of SBECD and SGD against CPZ-induced acute toxicity employing in vitro (SH-SY5Y neuroblastoma cells) and in vivo (zebrafish embryo) models. Our major findings and conclusions are the following: (1) both SBECD and SGD strongly relieved the cytotoxic effects of CPZ in SH-SY5Y cells. (2) SGD co-treatment did not affect or increase the CPZ-induced 24 h mortality in NMRI mice, while SBECD caused a protective effect in a dose-dependent fashion. (3) The binding constants of ligand-CD complexes and/or the in vitro protective effects of CDs can help to estimate the in vivo suitability of CDs as antidotes; however, some other factors can overwrite these predictions.

Analysis and Comparison of Rapid Methods for the Determination of Ochratoxin a Levels in Organs and Body Fluids Obtained from Exposed Mice.

Mycotoxins are bioaccumulative contaminants impacting animals and humans. The simultaneous detection of frequent active exposures and accumulated mycotoxin level (s) in exposed organisms would be the most ideal to enable appropriate actions. However, few methods are available for the purpose, and there is a demand for dedicated, sensitive, reliable, and practical assays. To demonstrate the issue, mice were exposed to a relevant agent Ochratoxin A (OTA), and accumulated OTA was measured by fine-tuned commercial assays. Quantitative high-performance liquid chromatography with fluorescence detection, enzyme-linked immunosorbent assay, and flow cytometry assays have been developed/modified using reagents available as commercial products when appropriate. Assays were performed on excised samples, and results were compared. Accumulated OTA could be detected and quantified; positive correlations (between applied doses of exposure and accumulated OTA levels and the results from assays) were found. Dedicated assays could be developed, which provided comparable results. The presence and accumulation of OTA following even a short exposure could be quantitatively detected. The assays performed similarly, but HPLC had the greatest sensitivity. Blood contained higher levels of OTA than liver and kidney. We demonstrate that specific but flexible and practical assays should be used for specific/local purposes, to measure the exposure itself and accumulation in blood or organs.

Testing the protective effects of cyclodextrins vs. alternariol-induced acute toxicity in HeLa cells and in zebrafish embryos.

Alternariol (AOH) is a mycotoxin produced by Alternaria fungi, it appears as a contaminant in tomatoes, grains, and grapes. The chronic exposure to AOH may cause carcinogenic and xenoestrogenic effects. Cyclodextrins (CDs) are cyclic oligosaccharides, they form host-guest complexes with apolar molecules. In this study, the interactions of AOH with CD monomers and polymers were examined employing fluorescence spectroscopy. Thereafter, the protective effects of certain CDs vs. AOH-induced toxicity were investigated on HeLa cells and on zebrafish embryos. Our major observations are the following: (1) Sugammadex forms highly stable complex with AOH (K = 4.8 ×104 L/mol). (2) Sugammadex abolished the AOH-induced toxicity in HeLa cells, while native ß-CD did not show relevant protective effect. (3) Each CD tested decreased the AOH-induced mortality and sublethal adverse effects in zebrafish embryos: Interestingly, native ß-CD showed the strongest protective impact in this model. (4) CD technology may be suitable to relieve AOH-induced toxicity.

Interaction of the Emerging Mycotoxins Beauvericin, Cyclopiazonic Acid, and Sterigmatocystin with Human Serum Albumin.

Beauvericin (BEA), cyclopiazonic acid (CPA), and sterigmatocystin (STC) are emerging mycotoxins. They appear as contaminants in food and animal feed, leading to economic losses and health risks. Human serum albumin (HSA) forms stable complexes with certain mycotoxins, including ochratoxins, alternariol, citrinin, and zearalenone. HSA binding can influence the toxicokinetics of xenobiotics, and albumin can also be considered and applied as a relatively cheap affinity protein. Therefore, we examined the potential interactions of BEA, CPA, and STC with HSA employing fluorescence spectroscopy, ultracentrifugation, ultrafiltration, and molecular modeling. Spectroscopic and ultracentrifugation studies demonstrated the formation of low-affinity BEA-HSA (Ka ≈ 103 L/mol) and moderately strong CPA-HSA and STC-HSA complexes (Ka ≈ 104 L/mol). In ultrafiltration experiments, CPA slightly displaced each site marker (warfarin, naproxen, and camptothecin) tested, while BEA and STC did not affect significantly the albumin binding of these drugs. Modeling studies suggest that CPA occupies Sudlow's site I, while STC binds to the Heme site (FA1) on HSA. Considering the interactions of CPA with the site markers, the CPA-HSA interaction may have toxicological importance.

In vitro characterization of the furin inhibitor MI-1851: Albumin binding, interaction with cytochrome P450 enzymes and cytotoxicity.

The substrate-analog furin inhibitor MI-1851 can suppress the cleavage of SARS-CoV-2 spike protein and consequently produces significant antiviral effect on infected human airway epithelial cells. In this study, the interaction of inhibitor MI-1851 was examined with human serum albumin using fluorescence spectroscopy and ultrafiltration techniques. Furthermore, the impacts of MI-1851 on human microsomal hepatic cytochrome P450 (CYP) 1A2, 2C9, 2C19, 2D6 and 3A4 activities were assessed based on fluorometric assays. The inhibitory action was also examined on human recombinant CYP3A4 enzyme and on hepatocytes. In addition, microsomal stability (60 min) and cytotoxicity were tested as well. MI-1851 showed no relevant interaction with human serum albumin and was significantly depleted by human microsomes. Furthermore, it did not inhibit CYP1A2, 2C9, 2C19 and 2D6 enzymes. In human hepatocytes, CYP3A4 was significantly suppressed by MI-1851 and weak inhibition was noticed in regard to human microsomes and human recombinant CYP3A4. Finally, MI-1851 did not impair the viability and the oxidative status of primary human hepatocytes (up to 100 µM concentration). Based on these observations, furin inhibitor MI-1851 appears to be potential drug candidates in the treatment of COVID-19, due to the involvement of furin in S protein priming and thus activation of the pandemic SARS-CoV-2.

Interactions of resveratrol and its metabolites (resveratrol-3-sulfate, resveratrol-3-glucuronide, and dihydroresveratrol) with serum albumin, cytochrome P450 enzymes, and OATP transporters.

Resveratrol (RES) is a widely-known natural polyphenol which is also contained by several dietary supplements. Large doses of RES can result in high micromolar levels of its sulfate and glucuronide conjugates in the circulation, due to the high presystemic metabolism of the parent polyphenol. Pharmacokinetic interactions of RES have been extensively studied, while only limited data are available regarding its metabolites. Therefore, in the current study, we examined the interactions of resveratrol-3-sulfate (R3S), resveratrol-3-glucuronide, and dihydroresveratrol (DHR; a metabolite produced by the colon microbiota) with human serum albumin (HSA), cytochrome P450 (CYP) enzymes, and organic anion transporting polypeptides (OATP) employing in vitro models. Our results demonstrated that R3S and R3G may play a major role in the RES-induced pharmacokinetic interactions: (1) R3S can strongly displace the site I marker warfarin from HSA; (2) R3G showed similarly strong inhibitory action on CYP3A4 to RES; (3) R3S proved to be similarly strong (OATP1B1/3) or even stronger (OATP1A2 and OATP2B1) inhibitor of OATPs tested than RES, while R3G and RES showed comparable inhibitory actions on OATP2B1.

Testing the extraction of 12 mycotoxins from aqueous solutions by insoluble beta-cyclodextrin bead polymer.

Mycotoxins are toxic metabolites of filamentous fungi; they are common contaminants in numerous foods and beverages. Cyclodextrins are ring-shaped oligosaccharides, which can form host-guest type complexes with certain mycotoxins. Insoluble beta-cyclodextrin bead polymer (BBP) extracted successfully some mycotoxins (e.g., alternariol and zearalenone) from aqueous solutions, including beverages. Therefore, in this study, we aimed to examine the ability of BBP to remove other 12 mycotoxins (including aflatoxin B1, aflatoxin M1, citrinin, dihydrocitrinone, cyclopiazonic acid, deoxynivalenol, ochratoxin A, patulin, sterigmatocystin, zearalanone, α-zearalanol, and ß-zearalanol) from different buffers (pH 3.0, 5.0, and 7.0). Our results showed that BBP can effectively extract citrinin, dihydrocitrinone, sterigmatocystin, zearalanone, α-zearalanol, and ß-zearalanol at each pH tested. However, for the removal of ochratoxin A, BBP was far the most effective at pH 3.0. Based on these observations, BBP may be a suitable mycotoxin binder to extract certain mycotoxins from aqueous solutions for decontamination and/or for analytical purposes.

In vitro interaction of potential antiviral TMPRSS2 inhibitors with human serum albumin and cytochrome P 450 isoenzymes.

The interactions of four sulfonylated Phe(3-Am)-derived inhibitors (MI-432, MI-463, MI-482 and MI-1900) of type II transmembrane serine proteases (TTSP) such as transmembrane protease serine 2 (TMPRSS2) were examined with serum albumin and cytochrome P450 (CYP) isoenzymes. Complex formation with albumin was investigated using fluorescence spectroscopy. Furthermore, microsomal hepatic CYP1A2, 2C9, 2C19 and 3A4 activities in presence of these inhibitors were determined using fluorometric assays. The inhibitory effects of these compounds on human recombinant CYP3A4 enzyme were also examined. In addition, microsomal stability assays (60-min long) were performed using an UPLC-MS/MS method to determine depletion percentage values of each compound. The inhibitors showed no or only weak interactions with albumin, and did not inhibit CYP1A2, 2C9 and 2C19. However, the compounds tested proved to be potent inhibitors of CYP3A4 in both assays performed. Within one hour, 20%, 12%, 14% and 25% of inhibitors MI-432, MI-463, MI-482 and MI-1900, respectively, were degraded. As essential host cell factor for the replication of the pandemic SARS-CoV-2, the TTSP TMPRSS2 emerged as an important target in drug design. Our study provides further preclinical data on the characterization of this type of inhibitors for numerous trypsin-like serine proteases.

Interactions of Mycotoxin Alternariol with Cytochrome P450 Enzymes and OATP Transporters.

Alternariol (AOH) is an emerging mycotoxin produced by Alternaria strains. The acute toxicity of the mycotoxin is low; however, chronic exposure to AOH may result in the development of endocrine disruptor and/or carcinogenic effects. The toxicokinetic properties of AOH have barely been characterized. Therefore, in this study, we aimed to investigate its interactions with CYP (1A2, 2C9, 2C19, 2D6, and 3A4) enzymes and OATP (1A2, 1B1, 1B3, and 2B1) transporters employing in vitro enzyme assays and OATP overexpressing cells, respectively. Our results demonstrated that AOH is a strong inhibitor of CYP1A2 (IC50 = 0.15 µM) and CYP2C9 (IC50 = 7.4 µM). Based on the AOH depletion assays in the presence of CYP enzymes, CYP1A2 is mainly involved, while CYP2C19 is moderately involved in the CYP-catalyzed biotransformation of the mycotoxin. AOH proved to be a strong inhibitor of each OATP transporter examined (IC50 = 1.9 to 5.4 µM). In addition, both direct and indirect assays suggest the involvement of OATP1B1 in the cellular uptake of the mycotoxin. These findings promote the deeper understanding of certain toxicokinetic interactions of AOH.

Effects of Microenvironmental Changes on the Fluorescence Signal of Alternariol: Magnesium Induces Strong Enhancement in the Fluorescence of the Mycotoxin.

Alternariol (AOH) is an emerging mycotoxin produced by Alternaria molds. It occurs as a contaminant e.g., in oilseeds, cereals, grapes, and tomatoes. Chronic exposure to AOH may cause genotoxic and endocrine disruptor effects. Our recent studies demonstrated that the fluorescence signal of AOH can be strongly affected by the environmental pH as well as by the presence of serum albumin or cyclodextrins. In the current study, we aimed to characterize the most optimal circumstances regarding the highly sensitive fluorescent detection of AOH. Therefore, the further detailed investigation of the microenvironment on the fluorescence signal of the mycotoxin has been performed, including the effects of different buffers, organic solvents, detergents, and cations. Organic solvents (acetonitrile and methanol) caused only slight increase in the emission signal of AOH, while detergents (sodium dodecyl sulfate and Triton-X100) and Ca2+ induced considerably higher enhancement in the fluorescence of the mycotoxin. In addition, Mg2+ proved to be a superior fluorescence enhancer of the AOH. Spectroscopic and modeling studies suggest the formation of low-affinity AOH-Mg2+ complexes. The effect of Mg2+ was also tested in two HPLC assays: Our results show that Mg2+ can considerably increase the fluorescence signal of AOH even in a chromatographic system.

Proof-of-Concept for the Analgesic Effect and Thermoregulatory Safety of Orally Administered Multi-Target Compound SZV 1287 in Mice: A Novel Drug Candidate for Neuropathic Pain.

SZV 1287 (3-(4,5-diphenyl-1,3-oxazol-2-yl)propanal oxime) is a novel multi-target candidate under preclinical development for neuropathic pain. It inhibits amine oxidase copper containing 3, transient receptor potential ankyrin 1 and vanilloid 1 (TRPV1) receptors. Mainly under acidic conditions, it is transformed to the cyclooxygenase inhibitor oxaprozin, which is ineffective for neuropathy. Therefore, an enterosolvent capsule is suggested for oral formulation, which we investigated for nociception, basic kinetics, and thermoregulatory safety in mice. The antihyperalgesic effect of SZV 1287 (10, 20, 50, and 200 mg/kg, p.o.) was determined in partial sciatic nerve ligation-induced traumatic neuropathy by aesthesiometry, brain and plasma concentrations by HPLC, and deep body temperature by thermometry. Its effect on proton-induced TRPV1 activation involved in thermoregulation was assessed by microfluorimetry in cultured trigeminal neurons. The three higher SZV 1287 doses significantly, but not dose-dependently, reduced neuropathic hyperalgesia by 50% of its maximal effect. It was quickly absorbed; plasma concentration was stable for 2 h, and it entered into the brain. Although SZV 1287 significantly decreased the proton-induced TRPV1-mediated calcium-influx potentially leading to hyperthermia, it did not alter deep body temperature. Oral SZV 1287 inhibited neuropathic hyperalgesia and, despite TRPV1 antagonistic action and brain penetration, it did not influence thermoregulation, which makes it a promising analgesic candidate.

Interaction of silymarin components and their sulfate metabolites with human serum albumin and cytochrome P450 (2C9, 2C19, 2D6, and 3A4) enzymes.

Silymarin is a mixture of flavonolignans isolated from the fruit of milk thistle (Silybum marianum (L.) Gaertner). Milk thistle extract is the active ingredient of several medications and dietary supplements to treat liver injury/diseases. After the oral administration, flavonolignans are extensively biotransformed, resulting in the formation of sulfate and/or glucuronide metabolites. Previous studies demonstrated that silymarin components form stable complexes with serum albumin and can inhibit certain cytochrome P450 (CYP) enzymes. Nevertheless, in most of these investigations, silybin was tested; while no or only limited information is available regarding other silymarin components and metabolites. In this study, the interactions of five silymarin components (silybin A, silybin B, isosilybin A, silychristin, and 2,3-dehydrosilychristin) and their sulfate metabolites were examined with human serum albumin and CYP (2C9, 2C19, 2D6, and 3A4) enzymes. Our results demonstrate that each compound tested forms stable complexes with albumin, and certain silymarin components/metabolites can inhibit CYP enzymes. Most of the sulfate conjugates were less potent inhibitors of CYP enzymes, but 2,3-dehydrosilychristin-19-O-sulfate showed the strongest inhibitory effect on CYP3A4. Based on these observations, the simultaneous administration of high dose silymarin with medications should be carefully considered, because milk thistle flavonolignans and/or their sulfate metabolites may interfere with drug therapy.

Inhibitory effects of polyphenols and their colonic metabolites on CYP2D6 enzyme using two different substrates.

Polyphenolic compounds (including flavonoids, chalcones, phenolic acids, and furanocoumarins) represent a common part of our diet, but are also the active ingredients of several dietary supplements and/or medications. These compounds undergo extensive metabolism by human biotransformation enzymes and the microbial flora of the colon. CYP2D6 enzyme metabolizes approximately 25% of the drugs, some of which has narrow therapeutic window. Therefore, its inhibition can lead to the development of pharmacokinetic interactions and the disruption of drug therapy. In this study, the inhibitory effects of 17 plant-derived compounds and 19 colonic flavonoid metabolites on CYP2D6 were examined, employing two assays with different test substrates. The O-demethylation of dextromethorphan was tested employing CypExpress 2D6 kit coupled to HPLC analysis; while the O-demethylation of another CYP2D6 specific substrate (AMMC) was investigated in a plate reader assay with BioVision Fluorometric CYP2D6 kit. Interestingly, some compounds (e.g., bergamottin) inhibited both dextromethorphan and AMMC demethylation; however, certain substances proved to be inhibitors only in one of the assays applied. Our results demonstrate that some polyphenols and colonic metabolites are inhibitors of CYP2D6-catalyzed reactions. Nevertheless, the inhibitory effects showed strong substrate dependence.

Interactions of zearalanone, α-zearalanol, ß-zearalanol, zearalenone-14-sulfate, and zearalenone-14-glucoside with serum albumin.

The xenoestrogenic mycotoxin zearalenone is a Fusarium-derived food and feed contaminant. In mammals, the reduced (e.g., zearalanone, α-zearalanol, and ß-zearalanol) and conjugated (e.g., zearalenone-14-sulfate) metabolites of zearalenone are formed. Furthermore, filamentous fungi and plants are also able to convert zearalenone to conjugated derivatives, including zearalenone-14-sulfate and zearalenone-14-glucoside, respectively. Serum albumin is the dominant plasma protein in the circulation; it interacts with certain mycotoxins, affecting their toxicokinetics. In a previous investigation, we demonstrated the remarkable species differences regarding the albumin binding of zearalenone and zearalenols. In the current study, the interactions of zearalanone, α-zearalanol, ß-zearalanol, zearalenone-14-sulfate, and zearalenone-14-glucoside with human, bovine, porcine, and rat serum albumins were examined, employing fluorescence spectroscopy and affinity chromatography. Zearalanone, zearalanols, and zearalenone-14-sulfate form stable complexes with albumins tested (K = 9.3 × 103 to 8.5 × 105 L/mol), while the albumin binding of zearalenone-14-glucoside seems to be weak. Zearalenone-14-sulfate formed the most stable complexes with albumins examined. Considerable species differences were observed in the albumin binding of zearalenone metabolites, which may have a role in the interspecies differences regarding the toxicity of zearalenone.

Inhibitory Effects of Quercetin and Its Main Methyl, Sulfate, and Glucuronic Acid Conjugates on Cytochrome P450 Enzymes, and on OATP, BCRP and MRP2 Transporters.

Quercetin is a flavonoid, its glycosides and aglycone are found in significant amounts in several plants and dietary supplements. Because of the high presystemic biotransformation of quercetin, mainly its conjugates appear in circulation. As has been reported in previous studies, quercetin can interact with several proteins of pharmacokinetic importance. However, the interactions of its metabolites with biotransformation enzymes and drug transporters have barely been examined. In this study, the inhibitory effects of quercetin and its most relevant methyl, sulfate, and glucuronide metabolites were tested on cytochrome P450 (CYP) (2C19, 3A4, and 2D6) enzymes as well as on organic anion-transporting polypeptides (OATPs) (OATP1A2, OATP1B1, OATP1B3, and OATP2B1) and ATP (adenosine triphosphate) Binding Cassette (ABC) (BCRP and MRP2) transporters. Quercetin and its metabolites (quercetin-3'-sulfate, quercetin-3-glucuronide, isorhamnetin, and isorhamnetin-3-glucuronide) showed weak inhibitory effects on CYP2C19 and 3A4, while they did not affect CYP2D6 activity. Some of the flavonoids caused weak inhibition of OATP1A2 and MRP2. However, most of the compounds tested proved to be strong inhibitors of OATP1B1, OATP1B3, OATP2B1, and BCRP. Our data demonstrate that not only quercetin but some of its conjugates, can also interact with CYP enzymes and drug transporters. Therefore, high intake of quercetin may interfere with the pharmacokinetics of drugs.

Effects of Chrysin and Its Major Conjugated Metabolites Chrysin-7-Sulfate and Chrysin-7-Glucuronide on Cytochrome P450 Enzymes and on OATP, P-gp, BCRP, and MRP2 Transporters.

Chrysin is an abundant flavonoid in nature, and it is also contained by several dietary supplements. Chrysin is highly biotransformed in the body, during which conjugated metabolites chrysin-7-sulfate and chrysin-7-glucuronide are formed. These conjugates appear at considerably higher concentrations in the circulation than the parent compound. Based on previous studies, chrysin can interact with biotransformation enzymes and transporters; however, the interactions of its metabolites have been barely examined. In this in vitro study, the effects of chrysin, chrysin-7-sulfate, and chrysin-7-glucuronide on cytochrome P450 enzymes (2C9, 2C19, 3A4, and 2D6) as well as on organic anion-transporting polypeptides (OATPs; 1A2, 1B1, 1B3, and 2B1) and ATP binding cassette [P-glycoprotein, multidrug resistance-associated protein 2, and breast cancer resistance protein (BCRP)] transporters were investigated. Our observations revealed that chrysin conjugates are strong inhibitors of certain biotransformation enzymes (e.g., CYP2C9) and transporters (e.g., OATP1B1, OATP1B3, OATP2B1, and BCRP) examined. Therefore, the simultaneous administration of chrysin-containing dietary supplements with medications needs to be carefully considered due to the possible development of pharmacokinetic interactions. SIGNIFICANCE STATEMENT: Chrysin-7-sulfate and chrysin-7-glucuronide are the major metabolites of flavonoid chrysin. In this study, we examined the effects of chrysin and its conjugates on cytochrome P450 enzymes and on organic anion-transporting polypeptides and ATP binding cassette transporters (P-glycoprotein, breast cancer resistance protein, and multidrug resistance-associated protein 2). Our results demonstrate that chrysin and/or its conjugates can significantly inhibit some of these proteins. Since chrysin is also contained by dietary supplements, high intake of chrysin may interrupt the transport and/or the biotransformation of drugs.

Probing the Interactions of Ochratoxin B, Ochratoxin C, Patulin, Deoxynivalenol, and T-2 Toxin with Human Serum Albumin.

Ochratoxins, patulin, deoxynivalenol, and T-2 toxin are mycotoxins, and common contaminants in food and drinks. Human serum albumin (HSA) forms complexes with certain mycotoxins. Since HSA can affect the toxicokinetics of bound ligand molecules, the potential interactions of ochratoxin B (OTB), ochratoxin C (OTC), patulin, deoxynivalenol, and T-2 toxin with HSA were examined, employing spectroscopic (fluorescence, UV, and circular dichroism) and ultrafiltration techniques. Furthermore, the influence of albumin on the cytotoxicity of these xenobiotics was also evaluated in cell experiments. Fluorescence studies showed the formation of highly stable OTB-HSA and OTC-HSA complexes. Furthermore, fluorescence quenching and circular dichroism measurements suggest weak or no interaction of patulin, deoxynivalenol, and T-2 toxin with HSA. In ultrafiltration studies, OTB and OTC strongly displaced the Sudlow's site I ligand warfarin, while other mycotoxins tested did not affect either the albumin binding of warfarin or naproxen. The presence of HSA significantly decreased or even abolished the OTB- and OTC-induced cytotoxicity in cell experiments; however, the toxic impacts of patulin, deoxynivalenol, and T-2 toxin were not affected by HSA. In summary, the complex formation of OTB and OTC with albumin is relevant, whereas the interactions of patulin, deoxynivalenol, and T-2 toxin with HSA may have low toxicological importance.