Regioselectivity of phase II metabolism of luteolin and quercetin by UDP-glucuronosyl transferases

A critical examination of human data for the biological activity of quercetin and its phase-2 conjugates

This critical review examines evidence for beneficial effects of quercetin phase-2 conjugates from clinical intervention studies, volunteer feeding trials, and in vitro work. Plasma concentrations of quercetin-3-O-glucuronide (Q3G) and 3'-methylquercetin-3-O-glucuronide (3'MQ3G) after supplementation may produce beneficial effects in macrophages and endothelial cells, respectively, especially if endogenous deglucuronidation occurs, and lower blood uric acid concentration via quercetin-3'-O-sulfate (Q3'S). Unsupplemented diets produce much lower concentrations (<50 nmol/l) rarely investigated in vitro. At 10 nmol/l, Q3'S and Q3G stimulate or suppress, respectively, angiogenesis in endothelial cells. Statistically significant effects have been reported at 100 nmol/l in breast cancer cells (Q3G), primary neuron cultures (Q3G), lymphocytes (Q3G and3'MQ3G) and HUVECs (QG/QS mixture), but it is unclear whether these translate to a health benefit in vivo. More sensitive and more precise methods to measure clinically significant endpoints are required before a conclusion can be drawn regarding effects at normal dietary concentrations. Future requirements include better understanding of inter-individual and temporal variation in plasma quercetin phase-2 conjugates, their mechanisms of action including deglucuronidation and desulfation both in vitro and in vivo, tissue accumulation and washout, as well as potential for synergy or antagonism with other quercetin metabolites and metabolites of other dietary phytochemicals.

Towards non-target proactive food safety: identification of active compounds in convenience tomato products by ten-dimensional hyphenation with integrated simulated gastrointestinal digestion

Current strategies for non-target food screening focus mainly on known hazardous chemicals (adulterants, residues, contaminants, packaging migrants, etc.) instead of bioactive constituents in general and exclude the biological effect detection. To widen the perspective, a more proactive non-target effect-directed strategy is introduced to complement food safety in order to detect not only known but also unknown bioactive compounds. The developed 10-dimensional hyphenation included on-surface digestion (1D), planar chromatographic separation (2D), visualization using white light (3D), UV light (4D), fluorescence light (5D), effect-directed assay analysis (6D), heart-cut zone elution to an orthogonal reversed phase column chromatography including online desalting (7D) with subsequent diode array detection (8D), high-resolution mass spectrometry (9D), and fragmentation (10D). Metabolism, i.e., intestinal digestion of each sample, was simulated and integrated on the same adsorbent surface to study any changes in the compound profiles. As proof of principle, nine convenience tomato products and a freshly prepared tomato soup were screened via five different planar assays in a non-targeted mode. Non-digested and digested samples were compared side by side. In their effect-directed profiles, 14 bioactive compounds from classes of lipids, plant hormones, spices, and pesticides were identified. In particular, bioactive compounds coming from the lipid class were increased by gastrointestinal digestion, while spices and pesticides remained unaffected. With regard to food safety, the determination of the two dinitrophenol herbicides dinoterb and dinoseb in highly processed tomato products should be given special attention. The hyphenation covered a broad analyte spectrum and showed robust and reliable results.

Anti-Proliferative Potential of Cynaroside and Orientin-In Silico (DYRK2) and In Vitro (U87 and Caco-2) Studies

Luteolin derivates are plant compounds with multiple benefits for human health. Stability to heat and acid hydrolysis and high resistance to (auto)oxidation are other arguments for the laden interest in luteolin derivates today. The present study was designed to compare the in silico and in vitro anti-proliferative potential of two luteolin derivates, luteolin-7-O-glucoside/cynaroside (7-Lut) and luteolin-8-C-glucoside/orientin (8-Lut). In silico investigations were carried out on the molecular target, namely, the human dual specificity tyrosine phosphorylation-regulated kinase 2 (DYRK2) in association with its natural ligand, curcumin (PDB ID: 5ZTN), by CLC Drug Discovery Workbench v. 1.5.1. software and Molegro Virtual Docker (MVD) v. MVD 2019.7.0. software. In vitro studies were performed on two human tumor cell lines, glioblastoma (U87) and colon carcinoma (Caco-2), respectively. Altogether, docking studies have revealed 7-Lut and 8-Lut as effective inhibitors of DYRK2, even stronger than the native ligand curcumin; in vitro studies indicated the ability of both luteolin glucosides to inhibit the viability of both human tumor cell lines, up to 85% at 50 and 100 µg/mL, respectively; the most augmented cytotoxic and anti-proliferative effects were obtained for U87 exposed to 7-Lut (IC50 = 26.34 µg/mL). The results support further studies on cynaroside and orientin to create drug formulas targeting glioblastoma and colon carcinoma in humans.

D-α-tocopherol polyethylene glycol 1000 succinate-based microemulsion delivery system: Stability enhancement of physicochemical properties of luteolin

In the present study, D-α-Tocopherol polyethylene glycol 1000 succinate-based self-microemulsifying drug delivery systems (TPGS-SMEDDS) were introduced to enhance the solubility and stability of luteolin. The ternary phase diagrams were constructed to obtain the maximum area of microemulsion and suitable formulations of TPGS-SMEDDS. The particle size distribution and polydispersity index of selected TPGS-SMEDDS were analyzed to be less than 100 nm and 0.4, respectively. The thermodynamic stability results suggested that the TPGS-SMEDDS was stable during the heat-cool and freeze-thaw cycle. Moreover, the TPGS-SMEDDS exhibited excellent encapsulation capacity (51.21 ± 4.39 to 85.71 ± 2.40%) and loading efficiency (61.46 ± 5.27 to 102.86 ± 2.88 mg/g) to luteolin. In addition, the TPGS-SMEDDS showed an admirable vitro release ability with a ratio of more than 88.40 ± 1.14% for luteolin in 24 h. Therefore, TPGS-based SMEDDS might provide an effective role for the oral administration of luteolin and holds promise as a potential delivery for poorly soluble bioactive compounds.

In Vitro Antiglycation and Methylglyoxal Trapping Effect of Peppermint Leaf (Mentha × piperita L.) and Its Polyphenols

The most significant reactive α-dicarbonyl RCS involved in the pathomechanism of glycation and related diseases is methylglyoxal (MGO). Hyperglycemia promotes the generation of MGO and leads to the formation of advanced glycation end products (AGEs). Therefore, MGO trapping and glycation inhibition appear to be important therapeutic targets in prediabetes, diabetes, and in the early prevention of hyperglycemic complications. Peppermint leaf is commonly used as herbal tea, rich in polyphenols. Eriocitrin, its predominant component, in a double-blind, randomized controlled study reversed the prediabetic condition in patients. However, the antiglycation activity of this plant material and its polyphenols has not been characterized to date. Therefore, the aim of this study was to evaluate the ability of a peppermint leaf dry extract and its polyphenols to inhibit non-enzymatic protein glycation in a model with bovine serum albumin (BSA) and MGO as a glycation agent. Peppermint polyphenols were also evaluated for their potential to trap MGO in vitro, and the resulting adducts were analyzed by UHPLC-ESI-MS. To relate chemical composition to glycation inhibitory activity, the obtained peppermint extract was subjected to qualitative and quantitative analysis. The capability of peppermint leaf polyphenols to inhibit glycation (27.3-77.2%) and form adducts with MGO was confirmed. In the case of flavone aglycones, mono- and di-adducts with MGO were observed, while eriodictyol and eriocitrin effectively produced only mono-adducts. Rosmarinic acid and luteolin-7-O-glycosides did not reveal this action. IC₅₀ of the peppermint leaf dry extract was calculated at 2 mg/mL, equivalent to a concentration of 1.8 μM/mL of polyphenols, including ~1.4 μM/mL of flavonoids and ~0.4 μM/mL of phenolic acids. The contribution of the four major components to the anti-AGE activity of the extract was estimated at 86%, including eriocitrin 35.4%, rosmarinic acid 25.6%, luteolin-7-O-rutinoside 16.9%, luteolin-7-O-β-glucuronoside 8.1%, and others 14%. The effect of peppermint dry extract and polyphenols in inhibiting MGO-induced glycation in vitro was comparable to that of metformin used as a positive control.

Low concentrations of Ambrosia maritima L. phenolic extract protect endothelial cells from oxidative cell death induced by H2O2 and sera from Crohn's disease patients

ETHNOPHARMACOLOGICAL RELEVANCE

A rising resort to herbal therapies in Crohn's disease (CD) alternative treatments has been recently observed due to their remarkable natural efficiency. In this context, the weed plant Ambrosia maritima L., traditionally known as Hachich el Aouinet in Algeria and as Damsissa in Egypt and Sudan, is widely used in North African folk medicine to treat infections, inflammatory diseases, gastrointestinal and urinary tract disturbances, rheumatic pain, respiratory problems, diabetes, hypertension and cancer.

AIM OF THE STUDY

To assess an Ambrosia maritima L. phenolic extract for its phenolic profile composition, its potential antioxidant activity in vitro, and its cytoprotective effect on cultured primary human endothelial cells (ECs) stressed with H₂O₂ and sera from CD patients.

MATERIALS AND METHODS

Phenolic compound extraction was performed with a low-temperature method. Extract chemical profile was attained by HPLC-DAD/ESI-MS. The extract in vitro antioxidant activity was assessed using several methods including cupric ion reducing power, DPPH radical scavenging assay, O-Phenanthroline free radical reducing activity, ABTS cation radical decolourisation assay, Galvinoxyl free radicals scavenging assay. Intracellular reactive oxygen species levels were evaluated in human endothelial cells by H₂DCFDA, while cell viability was assessed by MTT.

RESULTS

The phenolic compounds extraction showed a yield of 17.66% with three di-caffeoylquinic acid isomers detected for the first time in Ambrosia maritima L. Using different analytical methods, a significant in vitro antioxidant activity was reported for the Ambrosia maritima L. extract, with an IC₅₀ value of 14.33 ± 3.86 μg/mL for the Galvinoxyl antioxidant activity method. Challenged with ECs the Ambrosia maritima L. extract showed a biphasic dose-dependent effect on H₂O₂-treated cells, cytoprotective and antioxidant at low doses, and cytotoxic and prooxidant at high doses, respectively. Viability and ROS levels data also demonstrated a prooxidant and cytotoxic effect of CD sera on cultured ECs. Interestingly, 10 μg/mL of Ambrosia maritima L. extract was able to counteract both CD sera-induced oxidative stress and ECs death.

CONCLUSION

Our data indicated Ambrosia maritima L. as a source of bioactive phenolics potentially employable as a natural alternative for CD treatment.

Comparison of metabolism and biological properties among positional isomers of quercetin glucuronide in LPS- and RANKL-challenged RAW264.7 cells

The major quercetin metabolite, quercetin-3-glucuronide, exerts various biological activities, including anti-inflammatory effects. This study aimed to evaluate the metabolic profiles and biological properties of the positional isomers of quercetin monoglucuronides (Q3G, Q7G, Q3'G, and Q4'G) in activated macrophages. In addition to quercetin aglycone, Q7G was more cytotoxic than the other quercetin monoglucuronides (QGs), which corresponded to its lower stability under neutral pH conditions. Q3G was most effective in inhibiting both LPS-dependent induction of IL-6 and RANKL-dependent activation of tartrate-resistant acid phosphatase; however, Q3'G and Q4'G may also help exert biological activities without potential cytotoxicity. The deconjugation efficacy to generate quercetin aglycone differed among QGs, with the highest efficacy in Q3G. These results suggest that the chemical or biological properties and metabolic profiles may depend on the stability of QGs to generate quercetin aglycone using β-glucuronidase.

A Dietary Antioxidant Formulation Ameliorates DNA Damage Caused by γ-Irradiation in Normal Human Bronchial Epithelial Cells In Vitro

Antioxidants can be used as radioprotectants to reduce DNA damage due to exposure to radiation that could result in malignancies, including lung cancer. Mortality rates are consistently higher in lung cancer, which is usually diagnosed at later stages of cancer development and progression. In this preliminary study, we examined the potential of an antioxidant formulation (AOX2) to reduce DNA damage using a cell model of human normal bronchial epithelial cells (BEAS-2B). Cells were exposed to γ-irradiation or smoke-related hydrocarbon 4[(acetoxymethyl)nitrosamino]-1 (3-pyridyl) 1-butanone (NNKOAc) to induce DNA damage. We monitored intracellular reactive oxygen species (ROS) levels and evidence of genotoxic damage including DNA fragmentation ELISA, γ-H2AX immunofluorescence, and comet assays. Pre-incubation of the cells with AOX2 before exposure to γ-irradiation and NNKOAc significantly reduced DNA damage. The dietary antioxidant preparation AOX2 significantly reduced the induction of the tumor suppressor protein p53 and DNA damage-associated γ-H2AX phosphorylation by radiation and the NNKOAc treatment. Thus, AOX2 has the potential to act as a chemoprotectant by lowering ROS levels and DNA damage caused by exposure to radiation or chemical carcinogens.

High-Throughput Measurement and Machine Learning-Based Prediction of Collision Cross Sections for Drugs and Drug Metabolites

Drug metabolite identification is a bottleneck of drug metabolism studies due to the need for time-consuming chromatographic separation and structural confirmation. Ion mobility-mass spectrometry (IM-MS), on the other hand, separates analytes on a rapid (millisecond) time scale and enables the measurement of collision cross section (CCS), a unique physical property related to an ion's gas-phase size and shape, which can be used as an additional parameter for identification of unknowns. A current limitation to the application of IM-MS to the identification of drug metabolites is the lack of reference CCS values. In this work, we assembled a large-scale database of drug and drug metabolite CCS values using high-throughput in vitro drug metabolite generation and a rapid IM-MS analysis with automated data processing. Subsequently, we used this database to train a machine learning-based CCS prediction model, employing a combination of conventional 2D molecular descriptors and novel 3D descriptors, achieving high prediction accuracies (0.8-2.2% median relative error on test set data). The inclusion of 3D information in the prediction model enables the prediction of different CCS values for different protomers, conformers, and positional isomers, which is not possible using conventional 2D descriptors. The prediction models, dmCCS, are available at https://CCSbase.net/dmccs_predictions.

Metabolism, tissue distribution and excretion of taxifolin in rat

The metabolism, tissue distribution and excretion of taxifolin in rat after oral administration of taxifolin encapsulated zein-caseinate Nanoparticles (TZP) were studied. The isomerization of taxifolin in rat small intestine and colon was found. Besides isomers, 16 metabolites of taxifolin were identified in rat feces, plasma and urine by UPLC-QTOF-MS. In colon, taxifolin underwent the metabolism of hydration, dehydration and ring-fission through the gut microflora. The main metabolites of taxifolin found in plasma and urine were its sulfated, glucuronidated, and/or methylated products. The dynamic variation of taxifolin and its metabolites in tissues and urine were quantified by UPLC-QqQ-MS/MS. Taxifolin and its metabolites could be quickly absorbed and distributed in the tissues, and relatively low concentrations were found in the heart and brain. The feces excretion of taxifolin was determined by HPLC. The total excretion during 24 h was 2.83 ± 0.80% to its given does, and the maximum excretion was found during 8-10 h post administration. Compared with feces, the excretion of taxifolin and its metabolites in urine was much faster, and the total excretion was 1.96 ± 0.23% during 12 h.

Quercetin loaded liposomes modified with galactosylated chitosan prevent LPS/D-GalN induced acute liver injury

Quercetin (Que) has been proved to have various biological activities, including anti-oxidation, anti-inflammation and anti-virus, showing great potential in liver protection. However, its water insolubility leads to low bioavailability. Therefore, the development of a suitable drug delivery fashion is imminent. In recent years, liposomes have been widely used in the fields of drug delivery and gene transfer thanks to the cell membrane like structure, easy surface-modification and high encapsulation efficiency. Herein, we fabricated Que loaded anionic liposomes. Galactosylated chitosan (GC) was simply attached to the surfaces of liposomes through electrostatic adsorption to achieve targeted delivery by binding to asialoglycoprotein receptor (ASGPR). The results showed that Que loaded liposomes modified with GC (GC-Que-Lipo) could enrich the liver in mice through tail vein injection. Liposomes could achieve sustained drug release and GC-Que-Lipo promoted M2 polarization of macrophages. More importantly, it could maintain low content of AST, ALT, ALP and high level of GSH while reducing lipid oxidation, thereby protecting the liver from damage in acute liver injury model. In general, we expect to be able to acquire targeted and efficient delivery of quercetin through a facile approach, thus fulfill the prevention and treatment of liver diseases.

Paving Luteolin Therapeutic Potentialities and Agro-Food-Pharma Applications: Emphasis on In Vivo Pharmacological Effects and Bioavailability Traits

Luteolin is a naturally occurring secondary metabolite belonging to the class of flavones. As many other natural flavonoids, it is often found in combination with glycosides in many fruits, vegetables, and plants, contributing to their biological and pharmacological value. Many preclinical studies report that luteolin present excellent antioxidant, anticancer, antimicrobial, neuroprotective, cardioprotective, antiviral, and anti-inflammatory effects, and as a consequence, various clinical trials have been designed to investigate the therapeutic potential of luteolin in humans. However, luteolin has a very limited bioavailability, which consequently affects its biological properties and efficacy. Several drug delivery strategies have been developed to raise its bioavailability, with nanoformulations and lipid carriers, such as liposomes, being the most intensively explored. Pharmacological potential of luteolin in various disorders has also been underlined, but to some of them, the exact mechanism is still poorly understood. Given the great potential of this natural antioxidant in health, this review is aimed at providing an extensive overview on the in vivo pharmacological action of luteolin and at stressing the main features related to its bioavailability, absorption, and metabolism, while essential steps determine its absolute health benefits and safety profiles. In addition, despite the scarcity of studies on luteolin bioavailability, the different drug delivery formulations developed to increase its bioavailability are also listed here.

Potential of Vasoprotectives to Inhibit Non-Enzymatic Protein Glycation, and Reactive Carbonyl and Oxygen Species Uptake

Reactive carbonyl species (RCS) such as methylglyoxal (MGO) or glyoxal (GO) are the main precursors of the formation of advanced glycation end products (AGEs). AGEs are a major factor in the development of vascular complications in diabetes. Vasoprotectives (VPs) exhibit a wide range of activities beneficial to cardiovascular health. The present study aimed to investigate selected VPs and their structural analogs for their ability to trap MGO/GO, inhibit AGE formation, and evaluate their antioxidant potential. Ultra-high-performance liquid chromatography coupled with an electrospray ionization mass spectrometer (UHPLC-ESI-MS) and diode-array detector (UHPLC-DAD) was used to investigate direct trapping capacity and kinetics of quenching MGO/GO, respectively. Fluorimetric and colorimetric measurements were used to evaluate antiglycation and antioxidant action. All tested substances showed antiglycative effects, but hesperetin was the most effective in RCS scavenging. We demonstrated that rutin, diosmetin, hesperidin, and hesperetin could trap both MGO and GO by forming adducts, whose structures we proposed. MGO-derived AGE formation was inhibited the most by hesperetin, and GO-derived AGEs by diosmetin. High reducing and antiradical activity was confirmed for quercetin, rutin, hesperetin, and calcium dobesilate. Therefore, in addition to other therapeutic applications, some VPs could be potential candidates as antiglycative agents to prevent AGE-related complications of diabetes.

Bioaccessibility and Bioactivity of Cereal Polyphenols: A Review

Cereal bioactive compounds, especially polyphenols, are known to possess a wide range of disease preventive properties that are attributed to their antioxidant and anti-inflammatory activity. However, due to their low plasma concentrations after oral intake, there is controversy regarding their therapeutic benefits in vivo. Within the gastrointestinal tract, some cereal polyphenols are absorbed in the small intestine, with the majority accumulating and metabolised by the colonic microbiota. Chemical and enzymatic processes occurring during gastrointestinal digestion modulate the bioactivity and bioaccessibility of phenolic compounds. The interactions between the cereal polyphenols and the intestinal epithelium allow the modulation of intestinal barrier function through antioxidant, anti-inflammatory activity and mucin production thereby improving intestinal health. The intestinal microbiota is believed to have a reciprocal interaction with polyphenols, wherein the microbiome produces bioactive and bioaccessible phenolic metabolites and the phenolic compound, in turn, modifies the microbiome composition favourably. Thus, the microbiome presents a key link between polyphenol consumption and the health benefits observed in metabolic conditions in numerous studies. This review will explore the therapeutic value of cereal polyphenols in conjunction with their bioaccessibility, impact on intestinal barrier function and interaction with the microbiome coupled with plasma anti-inflammatory effects.

Inhibitory effects of quercetin and its major metabolite quercetin-3-O-β-D-glucoside on human UDP-glucuronosyltransferase 1A isoforms by liquid chromatography-tandem mass spectrometry

Quercetin is a flavonoid that is widely present in plant-derived food. Quercetin-3-O-β-D-glucoside (Q3GA) is a predominant metabolite of quercetin in animal and human plasma. The inhibitory effects of the UDP-glucuronosyl transferases (UGTs) caused by herbal components may be a key factor for the clinical assessment of herb-drug interactions (HDIs). The present study aimed to investigate the inhibitory profile of quercetin and Q3GA on recombinant UGT1A isoforms in vitro. The metabolism of the nonspecific substrate 4-methylumbelliferone (4-MU) by the UGT1A isoforms was assessed by liquid chromatography-tandem mass spectrometry. Preliminary screening experiments indicated that quercetin exhibited stronger inhibitory effects on UGT1A1, UGT1A3, UGT1A6 and UGT1A9 enzymes than Q3GA. Kinetic experiments were performed to characterize the type of inhibition caused by quercetin and Q3GA towards these UGT isoforms. Quercetin exerted non-competitive inhibition on UGT1A1 and UGT1A6, with half maximal inhibitory concentration (IC₅₀) values of 7.47 and 7.07 µM and inhibition kinetic parameter (K_i) values of 2.18 and 28.87 µM, respectively. Quercetin also exhibited competitive inhibition on UGT1A3 and UGT1A9, with IC₅₀ values of 10.58 and 2.81 µM and K_i values of 1.60 and 0.51 µM, respectively. However, Q3GA displayed weak inhibition on UGT1A1, UGT1A3 and UGT1A6 enzymes with IC₅₀ values of 45.21, 106.5 and 51.37 µM, respectively. In the present study, quercetin was a moderate inhibitor of UGT1A1 and UGT1A3, a weak inhibitor of UGT1A6, and a strong inhibitor on UGT1A9. The results of the present study suggested potential HDIs that may occur following quercetin co-administration with drugs that are mainly metabolized by UGT1A1, UGT1A3 and UGT1A9 enzymes.

Role of luteolin in overcoming Parkinson's disease

Parkinson's disease (PD) is the second most common neurodegenerative disorder affecting elderly people (>60 years old) worldwide. There is no permanent cure for the disease but the symptomatic relief can be obtained by using dopamine agonists besides L-dopa therapy. The longer use of the drugs is associated with several side effects. Hence, the researchers have made a considerable attention toward the development of neuroprotective agents from plants. A number of phytochemicals have been demonstrated for their protective effects in various in vitro, in vivo, and clinical studies. In this context, luteolin, a flavone which is present in fruits and vegetables has been attributed to a number of pharmacological properties including neuroprotective. The present review demonstrates the bioavailability, oral absorption, and mechanism of action against PD.

Potential Herb-Drug Interactions in the Management of Age-Related Cognitive Dysfunction

Late-life mild cognitive impairment and dementia represent a significant burden on healthcare systems and a unique challenge to medicine due to the currently limited treatment options. Plant phytochemicals have been considered in alternative, or complementary, prevention and treatment strategies. Herbals are consumed as such, or as food supplements, whose consumption has recently increased. However, these products are not exempt from adverse effects and pharmacological interactions, presenting a special risk in aged, polymedicated individuals. Understanding pharmacokinetic and pharmacodynamic interactions is warranted to avoid undesirable adverse drug reactions, which may result in unwanted side-effects or therapeutic failure. The present study reviews the potential interactions between selected bioactive compounds (170) used by seniors for cognitive enhancement and representative drugs of 10 pharmacotherapeutic classes commonly prescribed to the middle-aged adults, often multimorbid and polymedicated, to anticipate and prevent risks arising from their co-administration. A literature review was conducted to identify mutual targets affected (inhibition/induction/substrate), the frequency of which was taken as a measure of potential interaction. Although a limited number of drugs were studied, from this work, interaction with other drugs affecting the same targets may be anticipated and prevented, constituting a valuable tool for healthcare professionals in clinical practice.

Chrysoeriol Prevents TNFα-Induced CYP19 Gene Expression via EGR-1 Downregulation in MCF7 Breast Cancer Cells

Estrogen overproduction is closely associated with the development of estrogen receptor-positive breast cancer. Aromatase, encoded by the cytochrome P450 19 (CYP19) gene, regulates estrogen biosynthesis. This study aimed to identify active flavones that inhibit CYP19 expression and to explore the underlying mechanisms. CYP19 expression was evaluated using reverse transcription PCR, quantitative real-time PCR, and immunoblot analysis. The role of transcription factor early growth response gene 1 (EGR-1) in CYP19 expression was assessed using the short-hairpin RNA (shRNA)-mediated knockdown of EGR-1 expression in estrogen receptor-positive MCF-7 breast cancer cells. We screened 39 flavonoids containing 26 flavones and 13 flavanones using the EGR1 promoter reporter activity assay and observed that chrysoeriol exerted the highest inhibitory activity on tumor necrosis factor alpha (TNFα)-induced EGR-1 expression. We further characterized and demonstrated that chrysoeriol inhibits TNFα-induced CYP19 expression through inhibition of extracellular signal-regulated kinase 1/2 (ERK1/2)-mediated EGR-1 expression. Chrysoeriol may be beneficial as a dietary supplement for the prevention of estrogen receptor-positive breast cancer, or as a chemotherapeutic adjuvant in the treatment of this condition.

Bioavailability and Pharmaco-therapeutic Potential of Luteolin in Overcoming Alzheimer's Disease

Luteolin is a naturally occurring, yellow crystalline flavonoid found in numerous dietary supplements we frequently have in our meals. Studies in the last 2 decades have revealed its therapeutic potential to reduce the Alzheimer's disease (AD) symptoms in various in vitro and in vivo models. The anti-Alzheimer's potential of luteolin is attributed to its ability to suppress Aβ as well as tau aggregation or promote their disaggregation, down-regulate the expression of COX-2, NOS, MMP-9, TNF-α, interleukins and chemokines, reduce oxidative stress by scavenging ROS, modulate the activities of transcription factors CREB, cJun, Nrf-1, NF-κB, p38, p53, AP-1 and β-catenine and inhibiting the activities of various protein kinases. In several systems, luteolin has been described as a potent antioxidant and anti-inflammatory agent. In addition, we have also discussed about the bio-availability of the luteolin in the plasma. After being metabolized luteolin persists in plasma as glucuronides and sulphate-conjugates. Human clinical trials indicated no dose limiting toxicity when administered at a dose of 100 mg/day. Improvements in the formulations and drug delivery systems may further enhance the bioavailability and potency of luteolin. The current review describes in detail the data supporting these studies.

Low dose of luteolin activates Nrf2 in the liver of mice at start of the active phase but not that of the inactive phase

A flavone luteolin has various health-promoting activities. Several studies reported that high dose of luteolin activates the Nrf2/ARE pathway in the liver. However, the effect of the low dose of luteolin that can be taken from a dietary meal on the Nrf2 activation remain unclear. It is expected that the flavonoid metabolism possesses a circadian rhythm, since nutritional metabolism processes daily cycle. In this study we investigated whether an administration affects the Nrf2 activation. ICR mice were orally administered 0.01–10 mg/kg body weight of luteolin once a day for 7 days at two time-points: at the start of active phase (ZT12) or at that of inactive phase (ZT0). Luteolin increased the nuclear translocation of Nrf2, resulting in the increases in its target gene products HO-1 and NQO1 at ZT12 but not at ZT0. The expression level of Nrf2 was lower at ZT12 than at ZT0 in the liver. We also found that the level of luteolin aglycon in the plasma is higher at ZT12 than at ZT0. These results suggest that the low dose of luteolin can activate Nrf2 pathway and the aglycon form of luteolin may mainly contribute to activate the Nrf2 pathway at ZT12 in the liver.

Homology Modeling of Human Uridine-5'-diphosphate-glucuronosyltransferase 1A6 Reveals Insights into Factors Influencing Substrate and Cosubstrate Binding

The elimination of numerous endogenous compounds and xenobiotics via glucuronidation by uridine-5'-diphosphate glycosyltransferase enzymes (UGTs) is an essential process of the body's chemical defense system. UGTs have distinct but overlapping substrate preferences, but the molecular basis for their substrate specificity remains poorly understood. Three-dimensional protein structures can greatly enhance our understanding of the interactions between enzymes and their substrates, but because of the inherent difficulties in purifying and crystallizing integral endoplasmic reticulum membrane proteins, no complete mammalian UGT structure has yet been produced. To address this problem, we have created a homology model of UGT1A6 using I-TASSER to explore, in detail, the interactions of human UGT1A6 with its substrates. Ligands were docked into our model in the presence of the cosubstrate uridine-5'-diphosphate-glucuronic acid, interacting residues were examined, and poses were compared to those cocrystallized with various plant and bacterial glycosyltransferases (GTs). Our model structurally resembles other GTs, and docking experiments replicated many of the expected UGT-substrate interactions. Some bias toward the template structures' protein-substrate interactions and binding preferences was evident.

Metabolism and Pharmacokinetics of Phytochemicals in the Human Body

Background:

Phytochemicals are obtained from various plants and used for the treatment of diseases as both traditional and modern medicines. Poor bioavailability of phytochemicals is a major concern in applying phytochemicals as a therapeutic agent. It is, therefore, necessary to understand the metabolism and pharmacokinetics of phytochemicals for its implication as a therapeutic agent.

Methods:

Articles on the metabolism of phytochemicals from the PubMed database. The articles were classified into the digestion, absorption, metabolism, excretion, toxicity, and bioavailability of phytochemicals and the effect of gut microbiota on the metabolism of phytochemicals.

Results:

The metabolism of each phytochemical is largely dependent on the individual's digestive ability, membrane transporters, metabolizing enzymes and gut microbiota. Further, the form of the phytochemical and genetic make-up of the individual greatly influences the metabolism of phytochemicals.

Conclusion:

The metabolism of phytochemicals is mostly depended on the form of phytochemicals and individualspecific variations in the metabolism of phytochemicals. Understanding the metabolism and pharmacokinetics of phytochemicals might help in applying plant-based medicines for the treatment of various diseases.

Importance of OATP1B1 and 1B3 in the Liver Uptake of Luteolin and Its Consequent Glucuronidation Metabolites

Luteolin is a typical flavonoid and broadly distributed in the plants. Oral bioavailability of luteolin is low owing to extensive metabolism. Regioselective glucuronidation by UDP-glucuronosyltransferases (UGTs) and liver uptake by organic anion transporting polypeptides (OATPs) of luteolin and consequent glucuronidation metabolites were studied. Luteolin-3'-O-glucuronide (L-3'-G) and luteolin-7-O-glucuronide (L-7-G) were the major metabolites in human liver microsomes. Further study demonstrated that UGT1A9 played a predominant role in the glucuronidation of luteolin. Transporter study showed that OATP1B1- and 1B3-transfected cells selectively uptake L-3'-G into cells but not luteolin or L-7-G. After intravenous administration of luteolin to mice, the area under the curve of L-3'-G in the plasma was the highest among luteolin, L-3'-G, and L-7-G. In the liver, the concentration of L-3'-G was significantly greater than L-7-G. In conclusion, OATP1B1 and OATP1B3 play an important role in the liver disposition of luteolin and its glucuronidation metabolites.

Characterization of the Impact of Drug Metabolism on the Gas-Phase Structures of Drugs Using Ion Mobility-Mass Spectrometry

Conventional strategies for drug metabolite identification employ a combination of liquid chromatography-mass spectrometry (LC-MS), which offers higher throughput but provides limited structural information, and nuclear magnetic resonance spectroscopy, which can achieves the most definitive identification but lacks throughput. Ion mobility-mass spectrometry (IM-MS) is a rapid, two-dimensional analysis that separates ions on the basis of their gas-phase size and shape (reflected by collision cross section, CCS) and their mass-to-charge (m/z) ratios. The rapid nature of IM separation combined with the structural information provided by CCS make IM-MS a promising technique for obtaining more structural information on drug metabolites without sacrificing analytical throughput. Here, we present an in vitro biosynthesis coupled with IM-MS strategy for rapid generation and analysis of drug metabolites. Drug metabolites were generated in vitro using pooled subcellular fractions derived from human liver and analyzed using a rapid flow injection-IM-MS method. We measured CCS values for 19 parent drugs and their 37 metabolites generated in vitro (78 values in total), representing a wide variety of metabolic modifications. Post-IM fragmentation and computational modeling were used to support metabolite identifications and explore the structural characteristics driving behaviors observed in IM separation. Overall, we found the effects of metabolic modifications on the gas-phase structures of the metabolites to be highly dependent upon the structural characteristics of the parent compounds and the specific position of the modification. This in vitro biosynthesis coupled with rapid IM-MS analysis workflow represents a promising platform for rapid and high-confidence identification of drug metabolites, applicable at a large scale.

Comprehensive Analyses of Quercetin Conjugates by LC/MS/MS Revealed That Isorhamnetin-7- O-glucuronide-4'- O-sulfate Is a Major Metabolite in Plasma of Rats Fed with Quercetin Glucosides

Quercetin glycosides in the diet are absorbed and converted to glucuronides, sulfates, or mixed conjugates of glucuronide and sulfate in plasma. Physiological effects of quercetin conjugates (Q-conjugates) differ depending on the type and position of conjugation. We developed a comprehensive analysis of Q-conjugates, including mixed conjugates, by LC/MS/MS. The whole species of Q-conjugates in tail blood plasma was measured on days 1, 3, and 12 in rats fed a 0.24% quercetin glucoside-containing diet. Twenty-three Q-conjugate molecules were detected, and 16 Q-conjugates among these were quantified using standard compounds. The most abundant metabolite in the plasma was mixed conjugates, comprising isorhamnetin-7- O-glucuronide-4'- O-sulfate, followed by quercetin-7- O-glucuronide-4'- O-sulfate; together, they accounted for 86% of total Q-conjugates on day 12. The profile of quercetin conjugate species did not significantly change during 12 days. The total Q-conjugate molecules quantified by our method was comparable with the total Q-conjugates quantified using an enzymatic deconjugation method.

The UDP-Glycosyltransferase (UGT) Superfamily: New Members, New Functions, and Novel Paradigms

UDP-glycosyltransferases (UGTs) catalyze the covalent addition of sugars to a broad range of lipophilic molecules. This biotransformation plays a critical role in elimination of a broad range of exogenous chemicals and by-products of endogenous metabolism, and also controls the levels and distribution of many endogenous signaling molecules. In mammals, the superfamily comprises four families: UGT1, UGT2, UGT3, and UGT8. UGT1 and UGT2 enzymes have important roles in pharmacology and toxicology including contributing to interindividual differences in drug disposition as well as to cancer risk. These UGTs are highly expressed in organs of detoxification (e.g., liver, kidney, intestine) and can be induced by pathways that sense demand for detoxification and for modulation of endobiotic signaling molecules. The functions of the UGT3 and UGT8 family enzymes have only been characterized relatively recently; these enzymes show different UDP-sugar preferences to that of UGT1 and UGT2 enzymes, and to date, their contributions to drug metabolism appear to be relatively minor. This review summarizes and provides critical analysis of the current state of research into all four families of UGT enzymes. Key areas discussed include the roles of UGTs in drug metabolism, cancer risk, and regulation of signaling, as well as the transcriptional and posttranscriptional control of UGT expression and function. The latter part of this review provides an in-depth analysis of the known and predicted functions of UGT3 and UGT8 enzymes, focused on their likely roles in modulation of levels of endogenous signaling pathways.

An update on polyphenol disposition via coupled metabolic pathways

INTRODUCTION

Polyphenols, which are widely distributed in plants and the human diets, are known to have numerous biological activities. However, the low bioavailability of polyphenols is mediated by coupled metabolic pathways. Areas covered: The key role of the interplay between drug metabolic enzymes (DMEs) and efflux transporters (ETs), nuclear receptors (NRs), and intestinal microflora in the disposition of polyphenols is summarized. Expert opinion: ETs are shown to act as a 'revolving door', facilitating and/or controlling cellular polyphenol glucuronide/sulfate excretion. Elucidating the mechanisms underlying the glucuronidation/sulfation-transport interplay and structure-activity relationships (SAR) of glucuronide/sulfate efflux by an ET is important. Some new physiologically based pharmacokinetic (PBPK) models could be developed to predict the interplay between glucuronides/sulfates and ETs. Additionally, the combined actions of uridine-5'-diphosphate glucuronosyltransferases, ETs, and intestinal microflora/enterocyte-derived β-glucuronidase enable triple recycling (local, enteric, and enterohepatic recycling), thereby increasing the residence time of polyphenols and their glucuronides in the local intestine and liver. Further studies are necessary to explore these recycling mechanisms and interactions between polyphenols and the intestinal microbiota. Since NRs govern the inducible expression of target genes that encode DMEs and ETs. Determination of the regulation mechanism mediated by NRs using transgenic and knockout animals is still needed.

Differential Impact of Flavonoids on Redox Modulation, Bioenergetics, and Cell Signaling in Normal and Tumor Cells: A Comprehensive Review

SIGNIFICANCE

Flavonoids can interact with multiple molecular targets to elicit their cellular effects, leading to changes in signal transduction, gene expression, and/or metabolism, which can, subsequently, affect the entire cell and organism. Immortalized cell lines, derived from tumors, are routinely employed as a surrogate for mechanistic studies, with the results extrapolated to tissues in vivo. Recent Advances: We review the activities of selected flavonoids on cultured tumor cells derived from various tissues in comparison to corresponding primary cells or tissues in vivo, mainly using quercetin and flavanols (epicatechin and (-)-epigallocatechin gallate) as exemplars. Several studies have indicated that flavonoids could retard cancer progression in vivo in animal models as well as in tumor cell models.

CRITICAL ISSUES

Extrapolation from in vitro and animal models to humans is not straightforward given both the extensive conjugation and complex microbiota-dependent metabolism of flavonoids after consumption, as well as the heterogeneous metabolism of different tumors.

FUTURE DIRECTIONS

Comparison of data from studies on primary cells or in vivo are essential not only to validate results obtained from cultured cell models, but also to highlight whether any differences may be further exploited in the clinical setting for chemoprevention. Tumor cell models can provide a useful mechanistic tool to study the effects of flavonoids, provided that the limitations of each model are understood and taken into account in interpretation of the data.

Simultaneous collection of the portal and superior vena cava blood in conscious rats defined that intestinal epithelium is the major site of glucuronidation, but not sulfation and methylation, of quercetin

Quercetin is a flavonoid with many physiological effects. Absorbed quercetin is rapidly conjugated in the intestinal epithelium and liver. Different positional isomers of quercetin conjugates have different physiological properties. However, the mechanisms of quercetin conjugation in the intestine are not fully clarified. We examined the regioselective quercetin conjugate formation in the intestine after oral administration of quercetin glycosides, by simultaneous sampling of blood from the portal vein and superior vena cava, and quantifying various positional isomers of quercetin glucuronides and sulfates in conscious rats. Concentrations of quercetin glucuronides were higher in blood from the portal vein than the superior vena cava, showing that glucuronidation mainly occurred in the intestine. Such differences were not observed for quercetin sulfates. Regioselectivity of the intestinal glucuronidation in quercetin hydroxyl groups were 7- >3'- >3- >4'-OH. Quercetin was mainly sulfated on 3'-OH at 30 min, but on 4'-OH at 240 min.

Long-Term Administration of Conjugated Estrogen and Bazedoxifene Decreased Murine Fecal β-Glucuronidase Activity Without Impacting Overall Microbiome Community

Conjugated estrogens (CE) and Bazedoxifene (BZA) combination is used to alleviate menopause-associated symptoms in women. CE+BZA undergo first-pass-metabolism in the liver and deconjugation by gut microbiome via β-glucuronidase (GUS) enzyme inside the distal gut. To date, the impact of long-term exposure to CE+BZA on the gut microbiome or GUS activity has not been examined. Our study using an ovariectomized mouse model showed that CE+BZA administration did not affect the overall cecal or fecal microbiome community except that it decreased the abundance of Akkermansia, which was identified as a fecal biomarker correlated with weight gain. The fecal GUS activity was reduced significantly and was positively correlated with the abundance of Lactobacillaceae in the fecal microbiome. We further confirmed in Escherichia coli K12 and Lactobacillus gasseri ADH that Tamoxifen-, 4-hydroxy-Tamoxifen- and Estradiol-Glucuronides competed for GUS activity. Our study for the first time demonstrated that long-term estrogen supplementation directly modulated gut microbial GUS activity. Our findings implicate that long-term estrogen supplementation impacts composition of gut microbiota and microbial activity, which affects estrogen metabolism in the gut. Thus, it is possible to manipulate such activity to improve the efficacy and safety of long-term administered estrogens for postmenopausal women or breast cancer patients.

Bioavailability of Quercetin in Humans with a Focus on Interindividual Variation

After consumption of plant-derived foods or beverages, dietary polyphenols such as quercetin are absorbed in the small intestine and metabolized by the body, or they are subject to catabolism by the gut microbiota followed by absorption of the resulting products by the colon. The resulting compounds are bioavailable, circulate in the blood as conjugates with glucuronide, methyl, or sulfate groups attached, and they are eventually excreted in the urine. In this review, the various conjugates from different intervention studies are summarized and discussed. In addition, the substantial variation between different individuals in the measured quercetin bioavailability parameters is assessed in detail by examining published human intervention studies where sources of quercetin have been consumed in the form of food, beverages, or supplements. It is apparent that most reported studies have examined quercetin and/or metabolites in urine and plasma from a relatively small number of volunteers. Despite this limitation, it is evident that there is less interindividual variation in metabolites which are derived from absorption in the small intestine compared to catabolites derived from the action of microbiota in the colon. There is also some evidence that a high absorber of intact quercetin conjugates could be a low absorber of microbiota-catalyzed phenolics, and vice versa. From the studies reported so far, the reasons or causes of the interindividual differences are not clear, but, based on the known metabolic pathways, it is predicted that dietary history, genetic polymorphisms, and variations in gut microbiota metabolism would play significant roles. In conclusion, quercetin bioavailability is subject to substantial variation between individuals, and further work is required to establish if this contributes to interindividual differences in biological responses.

Defining Metabolic and Nonmetabolic Regulation of Histone Acetylation by NSAID Chemotypes

Nonsteroidal anti-inflammatory drugs (NSAIDs) are well-known for their effects on inflammatory gene expression. Although NSAIDs are known to impact multiple cellular signaling mechanisms, a recent finding is that the NSAID salicylate can disrupt histone acetylation, in part through direct inhibition of the lysine acetyltransferase (KAT) p300/CBP. While salicylate is a relatively weak KAT inhibitor, its CoA-linked metabolite is more potent; however, the ability of NSAID metabolites to inhibit KAT enzymes biochemically and in cells remains relatively unexplored. Here we define the role of metabolic and nonmetabolic mechanisms in inhibition of KAT activity by NSAID chemotypes. First, we screen a small panel of NSAIDs for biochemical inhibition of the prototypical KAT p300, leading to the finding that many carboxylate-containing NSAIDs, including ibuprofen, are able to function as weak inhibitors. Assessing the inhibition of p300 by ibuprofen-CoA, a known NSAID metabolite, reveals that linkage of ibuprofen to CoA increases its biochemical potency toward p300 and other KAT enzymes. In cellular studies, we find that carboxylate-containing NSAIDs inhibit histone acetylation. Finally, we exploit the stereoselective metabolism of ibuprofen to assess the role of its acyl-CoA metabolite in regulation of histone acetylation. This unique strategy reveals that formation of ibuprofen-CoA and histone acetylation are poorly correlated, suggesting metabolism may not be required for ibuprofen to inhibit histone acetylation. Overall, these studies provide new insights into the ability of NSAIDs to alter histone acetylation, and illustrate how selective metabolism may be leveraged as a tool to explore the influence of metabolic acyl-CoAs on cellular enzyme activity.

Absorption Properties of Luteolin and Apigenin in Genkwa Flos Using In Situ Single-Pass Intestinal Perfusion System in the Rat

The flower bud of Daphne genkwa (Genkwa Flos) is a commonly used herbal medicine in Asian countries. Luteolin and apigenin are two recognized active flavonoids in Genkwa Flos. The aim of this study was to investigate the intestinal absorption mechanisms of Genkwa Flos flavonoids using in situ single-pass intestinal perfusion rat model. Using HPLC, we determined its major effective flavonoids luteolin, apigenin, as well as, hydroxygenkwanin and genkwanin in biological samples. The intestinal absorption mechanisms of the total flavonoids in Genkwa Flos (TFG) were investigated using in situ single-pass intestinal perfusion rat model. Comparing the TFG absorption rate in different intestinal segments, data showed that the small intestine absorption was significantly higher than that of the colon ([Formula: see text]). Compared with duodenum and ileum, the jejunum was the best small intestinal site for TFG absorption. The high TFG concentration (61.48[Formula: see text][Formula: see text]g/ml) yielded the highest permeability ([Formula: see text]). Subsequently, three membrane protein inhibitors (verapamil, pantoprazole and probenecid) were used to explore the TFG absorption pathways. Data showed probenecid, a multidrug resistance protein (or MRP) inhibitor, effectively enhanced the TFG absorption ([Formula: see text]). Furthermore, by comparing commonly used natural absorption enhancers on TFG, it was observed that camphor was the most effective. In Situ single-pass intestinal perfusion experiment shows that TFG absorption is much higher in the small intestine than in the colon, and the TFG is absorbed mainly via an active transport pathway with MRP-mediated efflux mechanism. Camphor obviously enhanced the TFG absorption, and this could be an effective TFG formulation preparation method to increase clinical effectiveness after Genkwa Flos administration. Our study elucidated the TFG absorption mechanisms, and provided new information for its formulation preparation.

Glucuronidated Flavonoids in Neurological Protection: Structural Analysis and Approaches for Chemical and Biological Synthesis

Both plant and mammalian cells express glucuronosyltransferases that catalyze glucuronidation of polyphenols such as flavonoids and other small molecules. Oral administration of select polyphenolic compounds leads to the accumulation of the corresponding glucuronidated metabolites at μM and sub-μM concentrations in the brain, associated with amelioration of a range of neurological symptoms. Determining the mechanisms whereby botanical extracts impact cognitive wellbeing and psychological resiliency will require investigation of the modes of action of the brain-targeted metabolites. Unfortunately, many of these compounds are not commercially available. This article describes the latest approaches for the analysis and synthesis of glucuronidated flavonoids. Synthetic schemes include both standard organic synthesis, semisynthesis, enzymatic synthesis and use of synthetic biology utilizing heterologous enzymes in microbial platform organisms.

In vitro-in silico-based analysis of the dose-dependent in vivo oestrogenicity of the soy phytoestrogen genistein in humans

BACKGROUND AND PURPOSE

The in vivo oestrogenicity of genistein and its glycoside genistin is still under debate. The present study aimed to develop a physiologically based kinetic (PBK) model that provides insight in dose-dependent plasma concentrations of genistein aglycone and its metabolites and enables prediction of in vivo oestrogenic effective dose levels of genistein and genistin in humans.

EXPERIMENTAL APPROACH

A PBK model for genistein and genistin in humans was developed based on in vitro metabolic parameters. The model obtained was used to translate in vitro oestrogenic concentration-response curves of genistein to in vivo oestrogenic dose-response curves for intake of genistein and genistin.

KEY RESULTS

The model predicted that genistein-7-O-glucuronide was the major circulating metabolite and that levels of the free aglycone were generally low [0.5-17% of total plasma genistein at oral doses from 0.01 to 50 mg (kg·bw)^-1 ]. The predicted in vivo benchmark dose for 5% response values for oestrogenicity varied between 0.06 and 4.39 mg kg^-1 genistein. For genistin, these values were 1.3-fold higher. These values are in line with reported human data and show that oestrogenic responses can be expected at an Asian dietary and a supplementary intake, while intake resulting from a Western diet may not be effective.

CONCLUSIONS AND IMPLICATIONS

The present study shows how plasma concentrations of genistein and its metabolites and oestrogenic dose levels of genistein in humans can be predicted by combining in vitro oestrogenicity with PBK model-based reverse dosimetry, eliminating the need for human intervention studies.

Flavones: Food Sources, Bioavailability, Metabolism, and Bioactivity

Flavones are a class of flavonoids that are a subject of increasing interest because of their biological activities in vitro and in vivo. This article reviews the major sources of flavones and their concentrations in food and beverages, which vary widely between studies. It also covers the roles of flavones in plants, the influence of growing conditions on their concentrations, and their stability during food processing. The absorption and metabolism of flavones are also reviewed, in particular the intestinal absorption of both O- and C-glycosides. Pharmacokinetic studies in both animals and humans are described, comparing differences between species and the effects of glycosylation on bioavailability. Biological activity in animal models and human dietary intervention studies is also reviewed. A better understanding of flavone sources and bioavailability is needed to understand mechanisms of action and nutritional intervention.

Structural Pharmacokinetics of Polymethoxylated Flavones in Rat Plasma Using HPLC-MS/MS

The purpose of this study was to investigate the pharmacokinetics of the polymethoxylated flavonoids kumatakenin, pachypodol, and retusin, which contain two, three, or four methoxy substitutions, using a validated ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method in rats. The pharmacokinetic results demonstrated that the elimination half-lives for kumatakenin, pachypodol, and retusin were 30 ± 11.6, 39.4 ± 19.5, and 106.9 ± 26 min, respectively, for the low dose group and 54.5 ± 16.5, 33.8 ± 10, and 134.6 ± 34.7 min for the high dose group. The results suggested that the area under the curve values (AUC) for the analytes did not correlate with the number of methoxy groups. Pachypodol had the lowest AUC, which may have been correlated with lipophilicity, for both the low and high dose groups. In conclusion, the polymethoxylated flavonoid pachypodol is more hydrophilic than kumatakenin or retusin, which were correlated with the pharmacokinetic results.

Physiologically based kinetic modeling of hesperidin metabolism and its use to predict in vivo effective doses in humans

SCOPE

To develop a physiologically based kinetic (PBK) model that describes the absorption, distribution, metabolism, and excretion of hesperidin in humans, enabling the translation of in vitro concentration-response curves to in vivo dose-response curves.

METHODS AND RESULTS

The PBK model for hesperidin in humans was developed based on in vitro metabolic parameters. Hesperidin was predicted to mainly occur in the systemic circulation as different monoglucuronides. The plasma concentrations of hesperidin aglycone (hesperetin) was predicted to be <0.02 mg/L at an oral dose of 50 mg/kg bw. The developed PBK model allowed conversion of in vitro concentration-response curves for different effects to in vivo dose-response curves. The BMD₀₅ (benchmark dose for 5% response) values for protein kinase A inhibition ranged between 135 and 529 mg/kg bw hesperidin, and for inhibition of endothelial cell migration and prostaglandin E₂ and nitric oxide production ranged between 2.19 and 44 mg/kg bw hesperidin. These values are in line with reported human data showing in vivo effects by hesperidin and show that these effects may occur at Western dietary and supplementary intake of hesperidin.

CONCLUSIONS

The developed PBK model adequately predicts absorption, distribution, metabolism, and excretion of hesperidin in humans and allows to evaluate the human in vivo situation without the need for human intervention studies.