Metabolism and transport of the citrus flavonoid hesperetin in Caco-2 cell monolayers

Sweeteners Show a Plasticizing Effect on PVP K30-A Solution for the Hot-Melt Extrusion of Fixed-Dose Amorphous Curcumin-Hesperetin Solid Dispersions

The co-administration of curcumin and hesperetin might be beneficial in terms of neuroprotective activity; therefore, in this study, we attempted to develop a fixed-dose formulation comprising these two compounds in an amorphous state. The aim of obtaining an amorphous state was to overcome the limitations of the low solubility of the active compounds. First, we assessed the possibility of using popular sweeteners (erythritol, xylitol, and sorbitol) as plasticizers to reduce the glass transition temperature of PVP K30 to prepare the polymer-excipient blends, which allowed the preparation of amorphous solid dispersions via hot-melt extrusion at a temperature below the original glass transition of PVP K30. Erythritol proved to be the superior plasticizer. Then, we focused on the development of fixed-dose amorphous solid dispersions of curcumin and hesperetin. Powder X-ray diffraction and thermal analysis confirmed the amorphous character of dispersions, whereas infrared spectroscopy helped to assess the presence of intermolecular interactions. The amorphous state of the produced dispersions was maintained for 6 months, as shown in a stability study. Pharmaceutical parameters such as dissolution rate, solubility, and in vitro permeability through artificial membranes were evaluated. The best improvement in these features was noted for the dispersion, which contained 15% of the total content of the active compounds with erythritol used as the plasticizer.

Amorphous System of Hesperetin and Piperine-Improvement of Apparent Solubility, Permeability, and Biological Activities

The low bioaccessibility of hesperetin and piperine hampers their application as therapeutic agents. Piperine has the ability to improve the bioavailability of many compounds when co-administered. The aim of this paper was to prepare and characterize the amorphous dispersions of hesperetin and piperine, which could help to improve solubility and boost the bioavailability of both plant-origin active compounds. The amorphous systems were successfully obtained by means of ball milling, as confirmed by XRPD and DSC studies. What's more, the FT-IR-ATR study was used to investigate the presence of intermolecular interactions between the systems' components. Amorphization enhanced the dissolution rate as a supersaturation state was reached, as well as improving the apparent solubility of both compounds by 245-fold and 183-fold, respectively, for hesperetin and piperine. In the in vitro permeability studies simulating gastrointestinal tract and blood-brain barrier permeabilities, these increased by 775-fold and 257-fold for hesperetin, whereas they were 68-fold and 66-fold for piperine in the GIT and BBB PAMPA models, respectively. Enhanced solubility had an advantageous impact on antioxidant as well as anti-butyrylcholinesterase activities-the best system inhibited 90.62 ± 0.58% of DPPH radicals and 87.57 ± 1.02% butyrylcholinesterase activity. To sum up, amorphization considerably improved the dissolution rate, apparent solubility, permeability, and biological activities of hesperetin and piperine.

Systematic comparison of transcriptomes of Caco-2 cells cultured under different cellular and physiological conditions

There is a need for standardized in vitro models emulating the functionalities of the human intestinal tract to study human intestinal health without the use of laboratory animals. The Caco-2 cell line is a well-accepted and highly characterized intestinal barrier model, which has been intensively used to study intestinal (drug) transport, host-microbe interactions and chemical or drug toxicity. This cell line has been cultured in different in vitro models, ranging from simple static to complex dynamic microfluidic models. We aimed to investigate the effect of these different in vitro experimental variables on gene expression. To this end, we systematically collected and extracted data from studies in which transcriptome analyses were performed on Caco-2 cells grown on permeable membranes. A collection of 13 studies comprising 100 samples revealed a weak association of experimental variables with overall as well as individual gene expression. This can be explained by the large heterogeneity in cell culture practice, or the lack of adequate reporting thereof, as suggested by our systematic analysis of experimental parameters not included in the main analysis. Given the rapidly increasing use of in vitro cell culture models, including more advanced (micro) fluidic models, our analysis reinforces the need for improved, standardized reporting protocols. Additionally, our systematic analysis serves as a template for future comparative studies on in vitro transcriptome and other experimental data.

The effects of citrus flavonoids and their metabolites on immune-mediated intestinal barrier disruption using an in vitro co-culture model

Hesperidin and naringin are citrus flavonoids with known anti-oxidative and anti-inflammatory properties. Evidence from previous studies indicates that both these compounds and the metabolites that are formed during intestinal metabolism are able to exert beneficial effects on intestinal barrier function and inflammation. However, so far, studies investigating the relative contributions of the various compounds are lacking. Therefore, we assessed the effect of citrus flavonoids and their intestinal metabolites on immune-mediated barrier disruption in an in vitro co-culture model. Caco-2 cell monolayers were placed in co-culture with phorbol 12-myristate 13-acetate-stimulated THP-1-Blue™ NF-κB cells for 30 h. At baseline, the citrus flavonoids and their metabolites were added to the apical compartment (50 or 100 µM per compound). After 24 h, THP-1 cells were incubated with lipopolysaccharide (LPS) in the basolateral compartment for 6 h. Incubation with citrus flavonoids and their metabolites did not induce changes in transepithelial electrical resistance, fluorescein isothiocyanate-dextran 4 kDa permeation or gene expression of barrier-related genes for any of the compounds tested. After LPS stimulation, NF-κB activity was significantly inhibited by all compounds (100 µM) except for one metabolite (all P ≤ 0·03). LPS-induced production of the cytokines IL-8, TNF-α and IL-6 was inhibited by most compounds (all P < 0·05). However, levels of IL-1β were increased, which may contribute to the lack of an improved barrier effect. Overall, these results suggest that citrus flavonoids may decrease intestinal inflammation via reduction of NF-κB activity and that the parent compounds and their metabolites formed during intestinal metabolism are able to exert comparable effects.

Review of factors affecting citrus polyphenol bioavailability and their importance in designing in vitro, animal, and intervention studies

Evidence from in vitro, animal, and human studies links citrus fruit consumption with several health-promoting effects. However, many in vitro studies disregard bioavailability data, a key factor determining responses in humans. Citrus (poly)phenol metabolism and bioavailability follow specific pathways that vary widely among individuals and are affected by several intrinsic (age, sex, gut microbiota, metabolic state, genetic polymorphisms) and extrinsic (food matrix, co-consumed food, (poly)phenol solubility, dose, food processing, lifestyle) factors. The gut microbiota is crucial to both absorption of citrus (poly)phenols and the production of catabolites, and absorption of both takes place mostly in the colon. Citrus (poly)phenol absorption can reach up to 100% in some individuals when the sum of the gut microbiota products are taken into account. This review emphasizes the importance of understanding citrus (poly)phenol absorption, metabolism, and bioavailability using evidence primarily derived from human studies in designing in vitro, animal, and further human clinical studies.

Novel O-Methylglucoside Derivatives of Flavanone in Interaction with Model Membrane and Transferrin

Flavonoids were biotransformed using various microorganisms, in order to obtain new compounds with potentially high biological activity. The aim of this work was to determine and compare the biological activity of four novel 6-methylflavanone O-methylglucosides. The tested compounds have the same flavonoid core structure and an attached O-methylglucose and hydroxyl group at different positions of ring A or B. The studies on their biological activity were conducted in relation to phosphatidylcholine membrane, erythrocytes and their membrane, and with human transferrin. These studies determined the compounds' toxicity and their impact on the physical properties of the membranes. Furthermore, the binding ability of the compounds to holo-transferrin was investigated. The obtained results indicate that used compounds bind to erythrocytes, change their shape and decrease osmotic fragility but do not disrupt the membrane structure. Furthermore, the used compounds ordered the area of the polar heads of lipids and increased membrane fluidity. However, the results indicate the binding of these compounds in the hydrophilic region of the membranes, like other flavonoid glycosides. The used flavanones formed complexes with transferrin without inducing conformational changes in the protein's structure. The relationship between their molecular structure and biological activity was discussed.

Association between Single Nucleotide Polymorphisms of SULT1A1, SULT1C4, ABCC2 and Phase II Flavanone Metabolites Excretion after Orange Juice Intake

Citrus fruits and juices are a major source of dietary flavanones, and the regular consumption of these foods is inversely associated with the development of cardiometabolic diseases. However, the biological benefits depend on the bioavailability of these compounds, and previous studies have reported a large interindividual variability in the absorption and excretion of these compounds. Different factors, such as age, gender or genetic polymorphism of genes coding enzymes involved in the metabolism and transport of the flavanones, may explain this heterogeneity. This study aimed to assess the impact of single nucleotide polymorphism of sulfotransferases SULT1A1 and SULT1C4, and ABCC2 transporter genes on excretion of phase II flavanone metabolites in volunteers after 24 h of orange juice intake. Forty-six volunteers ingested a single dose of 500 mL of orange juice and 24-h urine was collected. The hesperetin and naringenin phase II metabolites were quantified in urine, and SNPs in SULT1A1, SULT1C4 and ABCC2 genes were genotyped. A significant (p < 0.05) relationship between the SNPs in these genes and the high excretion of phase II flavanone metabolites were observed. These results identified novel polymorphisms associated with higher absorption of flavanones, which may provide bases for future personalized nutritional guidelines for consuming flavanone-rich foods rich in these nutrients for better benefit from their health properties.

Hesperetin, a Promising Treatment Option for Diabetes and Related Complications: A Literature Review

The morbidity and mortality of diabetes have increased dramatically in recent decades. Novel strategies for treating diabetes and its complications with minimal side effects are in urgent need. New monomeric molecules extracted from herbal medicine, which is a form of alternative medicine, are being sought as drug candidates for the treatment of diabetes and its complications. Hesperetin (Hst), a citrus flavonoid, is of increasing interest in scientific studies recently due to its properties in combating diabetes and its complications, whereas existing studies are scattered and unsystematic. Here, we summarized the literature studies over the last 10 years to review the potential therapeutic role of Hst in the prevention and mitigation of diabetes and its complications, intending to provide promising strategies for the clinical management of diabetes and its complications.

Hesperidin and its aglycone hesperetin in breast cancer therapy: A review of recent developments and future prospects

Breast cancer (BC) has high incidence and mortality rates, making it a major global health issue. BC treatment has been challenging due to the presence of drug resistance and the limited availability of therapeutic options for triple-negative and metastatic BC, thereby urging the exploration of more effective anti-cancer agents. Hesperidin and its aglycone hesperetin, two flavonoids from citrus species, have been extensively evaluated for their anti-cancer potentials. In this review, available literatures on the chemotherapeutic and chemosensitising activities of hesperidin and hesperetin in preclinical BC models are reported. The safety and bioavailability of hesperidin and hesperetin as well as the strategies to enhance their bioavailability are also discussed. Overall, hesperidin and hesperetin can inhibit cell proliferation, migration and BC stem cells as well as induce apoptosis and cell cycle arrest in vitro. They can also inhibit tumour growth, metastasis and neoplastic changes in tissue architecture in vivo. Moreover, the co-administration of hesperidin or hesperetin with doxorubicin, letrozole or tamoxifen can enhance the efficacies of these clinically available agents. These chemotherapeutic and chemosensitising activities of hesperidin and hesperetin have been linked to several mechanisms, including the modulation of signalling pathways, glucose uptake, enzymes, miRNA expression, oxidative status, cell cycle regulatory proteins, tumour suppressor p53, plasma and liver lipid profiles as well as DNA repair mechanisms. However, poor water solubility, extensive phase II metabolism and apical efflux have posed limitations to the bioavailability of hesperidin and hesperetin. Various strategies for bioavailability enhancement have been studied, including the utilisation of nano-based drug delivery systems and the co-administration of hesperetin with other flavonoids. In particular, nanoformulated hesperidin and hesperetin possess greater chemotherapeutic and chemosensitising activities than free compounds. Despite promising preclinical results, further safety and efficacy evaluation of hesperidin and hesperetin as well as their nanoformulations in clinical trials is required to ascertain their potentials to be developed as clinically useful agents for BC treatment.

Negligible Effect of Quercetin in the Pharmacokinetics of Sulfasalazine in Rats and Beagles: Metabolic Inactivation of the Interaction Potential of Quercetin with BCRP

Breast cancer resistance protein (BCRP) mediates pharmacokinetic drug interactions. This study evaluated the potential of quercetin to inhibit and induce BCRP in vitro and in vivo. The inhibition of BCRP was investigated for quercetin and its metabolites using BCRP/mBcrp1-overexpressing MDCKII cells by flow cytometry. The induction of BCRP was investigated in LS174T cells using quantitative PCR. The expression of rat BCRP in rat small intestine, liver, and kidney was also measured after multiple administrations of quercetin in rats (50, 100, and 250 mg/kg, seven days). The in vivo pharmacokinetic changes of sulfasalazine following single or multiple administration of quercetin in rats and beagles were investigated. Although the induction effect of quercetin on BCRP was observed in vitro, the in vivo expression of rat BCRP was not changed by multiple quercetin administrations. Oral administration of quercetin did not affect the plasma concentration or pharmacokinetic parameters of sulfasalazine, regardless of dose and dosing period in either rats or beagles. In addition, the inhibitory effect of quercetin metabolites on BCRP/mBcrp1 was not observed. These results suggest that the in vivo drug interaction caused by quercetin via BCRP was negligible, and it may be related to the metabolic inactivation of quercetin for the inhibition of BCRP.

Microbial Phosphorylation Product of Hesperetin by Bacillus subtilis BCRC 80517 Improves Oral Bioavailability in Rats

The flavanoid hesperidin (Hsd) is one of the major polyphenols in citrus fruits. Hsd and its aglycone hesperetin (Hst) have a broad array of bioactivities; however, their low aqueous solubility and low intestinal permeability lead to their limited oral bioavailability. In the present study, we generated two water-soluble derivatives of Hst, namely, Hst 7-O-phosphate and Hst3'-O-phosphate, by a unique bioconversion process of Bacillus subtilis var. natto BCRC80517. The phosphorylated products showed superior aqueous solubility and distinct physicochemical properties compared with the original Hst. The Hst phosphate derivatives (HstPs) remained stable in simulated gastric and intestinal fluids for 240 min and could revert to the original Hst form by alkaline phosphatase treatment in Caco-2 cells, showing enhanced intestinal permeability in vitro. After oral administration in rats, HstPs greatly elevated plasma exposure to Hst and showed better bioavailability than did Hsd. HstPs may be a potential and efficient alternative to Hst.

Extensive metabolism of flavonoids relevant to their potential efficacy on Alzheimer's disease

Alzheimer's disease (AD) is an age-related neurodegenerative disorder, the incidence of which is climbing with ever-growing aged population, but no cure is hitherto available. The epidemiological studies unveiled that chronic intake of flavonoids was negatively associated with AD risk. Flavonoids, a family of natural polyphenols widely distributed in human daily diets, were readily conjugated by phase II drug metabolizing enzymes after absorption in vivo, and glucuronidation could occur in 1 min following intravenous administration. Recently, as many as 191 metabolites were obtained after intragastric administration of a single flavonoid, indicating that other bioactive metabolites, besides conjugates, might be formed and account for the contradiction between efficacy of flavonoids in human or animal models and low systematic exposure of flavonoid glycosides or aglycones. In this review, metabolism of complete 68 flavonoid monomers potential for AD treatment, grouped in flavonoid O-glycosides, flavonoid aglycones, flavonoid C-glycosides, flavonoid dimers, flavonolignans and prenylated flavonoids according to their common structural elements, respectively, has been systematically retrospected, summarized and discussed, including their unequivocally identified metabolites, metabolic interconversions, metabolic locations, metabolic sites (regio- or stereo-selectivity), primarily involved metabolic enzymes or intestinal bacteria, and interspecies correlations or differences in metabolism, and their bioactive metabolites and the underlying mechanism to reverse AD pathology were also reviewed, providing whole perspective about advances on extensive metabolism of diverse potent flavonoids in vivo and in vitro up to date and aiming at elucidation of mechanism of actions of flavonoids on AD or other central nervous system (CNS) disorders.

Contribution of Biotransformations Carried Out by the Microbiota, Drug-Metabolizing Enzymes, and Transport Proteins to the Biological Activities of Phytochemicals Found in the Diet

The consumption of dietary phytochemicals has been associated with several health benefits and relevant biological activities. It is postulated that biotransformations of these compounds regulated by the microbiota, Phase I/II reactions, transport proteins, and deconjugating enzymes contribute not only to their metabolic clearance but also, in some cases, to their bioactivation. A number of factors (age, genetics, sex, physiopathological conditions, and the interplay with other dietary phytochemicals) modulating metabolic activities are important sources and contributors to the interindividual variability observed in clinical studies evaluating the biological activities of phytochemicals. In this review, we discuss all the processes that can affect the bioaccessibility and beneficial effects of these bioactive compounds. Herein, we argue that the role of these factors must be further studied to correctly understand and predict the effects observed following the intake of phytochemicals. This is, in particular, with regard to in vitro investigations, which have shown great inconsistency with preclinical and clinical studies. The complexity of in vivo metabolic activity and biotransformation should therefore be considered in the interpretation of results in vitro and their translation to human physiopathology.

Mechanism of the Intestinal Absorption of Six Flavonoids from Zizyphi Spinosi Semen Across Caco-2 Cell Monolayer Model

BACKGROUND

Flavonoid compounds are one kind of active ingredients isolated from a traditional Chinese herb Zizyphi spinosae semen (ZSS). Studies have shown that ZSS flavonoids have significant antioxidant effects.

METHODS

In this study, the Caco-2 cell monolayer model was constructed to investigate the intestinal absorption characteristics and mechanism of Isovitexin (IV), Swertisin (ST), Isovitexin-2''-O-β-D-glucopyranoside (IVG), Spinosin (S), 6'''-p-coumaroylspinosin (6-CS) and 6'''-feruloylspinosin (6-FS).

RESULTS

The results of the bidirectional transport assay showed that the six flavonoids have good intestinal absorption in a near-neutral and 37°C environment, and the absorbability in descending order was 6-FS>6- CS>IVG>S>IV>ST. The results of carrier inhibition experiments and transport kinetics indicated that the absorption mechanism of six flavonoids was energy-dependent monocarboxylate transporter (MCT)-mediated active transport. In particular, the para-cellular pathway also participated in the transport of IV, ST, IVG and S. Furthermore, the efflux process of six flavonoids was mediated by P-glycoprotein (P-gp) and multidrug resistance protein (MRP), which may result in a decrease of bioavailability.

CONCLUSION

Our findings provide significant information for revealing the relationship between the intestinal absorption mechanism of flavonoids and its structure as well as laying a basis for the research of flavonoid preparations.

The biological fate and bioefficacy of citrus flavonoids: bioavailability, biotransformation, and delivery systems

Citrus fruits are among the most popularly consumed fruits worldwide, including oranges, grapefruits, pomelos and lemons. Citrus flavonoids such as hesperidin, naringin and nobiletin have shown an array of health benefits in cell, animal and clinical studies, including antioxidative, anti-inflammatory, neuroprotective, anticancer, and anti-obesity activities. Citrus flavonoids have limited bioavailability after oral administration, leaving the major part unabsorbed and persisted in the colon. Recent studies have highlighted the important role of the gut microbiota and in vivo biotransformation on the bioactivity of citrus flavonoids. This article discusses the biological fate of citrus flavonoids from the viewpoint of their absorption, distribution, metabolism and excretion in vivo. Many delivery systems have been designed to enhance the oral bioavailability of citrus flavonoids, such as emulsions, self-emulsifying systems, nanoparticles and solid dispersions. The ultimate goal of these delivery systems is to enhance the bioefficacy of citrus flavonoids. Several studies have found that the increased bioavailability leads to enhanced bioefficacy of citrus flavonoids in specific animal models. Regarding the complex dynamics of citrus flavonoids and gut microbiota, the bioavailability-bioactivity relationship is an interesting but under-discussed area. Comprehensively understanding the biological fate and bioefficacy of citrus flavonoids would be helpful to develop functional foods with better health benefits.

Stratification of Volunteers According to Flavanone Metabolite Excretion and Phase II Metabolism Profile after Single Doses of 'Pera' Orange and 'Moro' Blood Orange Juices

Large interindividual variations in the biological response to citrus flavanones have been observed, and this could be associated with high variations in their bioavailability. The aim of this study was to identify the main determinants underlying interindividual differences in citrus flavanone metabolism and excretion. In a randomized cross-over study, non-obese and obese volunteers, aged 19-40 years, ingested single doses of Pera and Moro orange juices, and urine was collected for 24 h. A large difference in the recovery of the urinary flavanone phase II metabolites was observed, with hesperetin-sulfate and hesperetin-sulfo-O-glucuronide being the major metabolites. Subjects were stratified according to their total excretion of flavanone metabolites as high, medium, and low excretors, but the expected correlation with the microbiome was not observed at the genus level. A second stratification was proposed according to phase II flavanone metabolism, whereby participants were divided into two excretion groups: Profiles A and B. Profile B individuals showed greater biotransformation of hesperetin-sulfate to hesperetin-sulfo-O-glucuronide, as well as transformation of flavanone-monoglucuronide to the respective diglucuronides, suggestive of an influence of polymorphisms on UDP-glucuronosyltransferase. In conclusion, this study proposes a new stratification of volunteers based on their metabolic profiles. Gut microbiota composition and polymorphisms of phase II enzymes may be related to the interindividual variability of metabolism.

Physiological relevance of food antioxidants

Dietary antioxidants are associated with prevention of oxidative stress related chronic diseases including certain types of cancer, cardiovascular diseases, diabetes, and neurodegenerative diseases. In recent years, there has been a growing interest in extending the knowledge on their physiological effects in human body. There are numbers of epidemiological, clinical, meta-analysis, and in vitro studies to explain formation mechanisms of each chronic diseases as well as the potential effects of dietary antioxidants on these diseases and gut health. Comprehensive studies for food antioxidants' journey from dietary intake to target tissues/organs deserve a serious consideration to have a clear understanding on the physiological effects of dietary antioxidants. Therefore, absorption and metabolism of dietary antioxidants, and the factors affecting their absorption, such as solubility of antioxidants, food matrix, and interaction between antioxidants have been evaluated in several research articles. This chapter provides an overview about potential health effects of dietary antioxidants considering with their absorption and metabolism in human body.

In Vitro Metabolism of Isopropylated and tert-Butylated Triarylphosphate Esters Using Human Liver Subcellular Fractions

Isopropylated and tert-butylated triarylphosphate esters (ITPs and TBPPs, respectively) are plasticizers and flame retardants that are ubiquitous in indoor environments; however, no studies to date have characterized their metabolism. Using human liver subcellular S9 fractions, phase I and II in vitro metabolism of triphenyl phosphate (TPHP), 4-tert-butylphenyl diphenyl phosphate (4tBPDPP), 2-isopropylphenyl diphenyl phosphate (2IPPDPP), and 4-isopropylphenyl diphenyl phosphate (4IPPDPP) was investigated at 1 and 10 μM doses. Parent depletion and the formation of known or suspected metabolites (e.g., likely hydrolysis or hydroxylated products), including diphenyl phosphate (DPHP), hydroxyl-triphenyl phosphate (OH-TPHP), isopropylphenyl phenyl phosphate (ip-PPP), and tert-butylphenyl phenyl phosphate (tb-PPP), were monitored and quantified via GC/MS or LC-MS/MS. tb-PPP and its conjugates were identified as the major in vitro metabolites of 4tBPDPP and accounted for 71% and 49%, respectively, of the parent molecule that was metabolized during the incubation. While the mass balance between parents and metabolites was conserved for TPHP and 4tBPDPP, approximately 20% of the initial parent mass was unaccounted for after quantifying suspected metabolites of 2IPPDPP and 4IPPDPP that had authentic standards available. Two novel ITP metabolites, mono-isopropenylphenyl diphenyl phosphate and hydroxy-isopropylphenyl diphenyl phosphate, were tentatively identified by high-resolution mass spectrometry and screened for in recently collected human urine where mono-isopropenylphenyl diphenyl phosphate was detected in one of nine samples analyzed. This study provides insight into the biological fate of ITP and TBPP isomers in human tissues and is useful in identifying appropriate biomarkers of exposure to monitor, particularly in support of epidemiological studies.

Flavonoids and type 2 diabetes: Evidence of efficacy in clinical and animal studies and delivery strategies to enhance their therapeutic efficacy

Diabetes mellitus type 2 (T2DM) is a metabolic disorder develops due to the overproduction of free radicals where oxidative stress could contribute it. Possible factors are defective insulin signals, glucose oxidation, and degradation of glycated proteins as well as alteration in glutathione metabolism which induced hyperglycemia. Previous studies revealed a link between T2DM with oxidative stress, inflammation and insulin resistance which are assumed to be regulated by numerous cellular networks such as NF-κB, PI3K/Akt, MAPK, GSK3 and PPARγ. Flavonoids are ubiquitously present in the nature and classified according to their chemical structures for example, flavonols, flavones, flavan-3-ols, anthocyanidins, flavanones, and isoflavones. Flavonoids indicate poor bioavailability which could be improved by employing various nano-delivery systems against the occurrences of T2DM. These bioactive compounds exert versatile anti-diabetic activities via modulating targeted cellular signaling networks, thereby, improving glucose metabolism, α -glycosidase, and glucose transport or aldose reductase by carbohydrate metabolic pathway in pancreatic β-cells, hepatocytes, adipocytes and skeletal myofibres. Moreover, anti-diabetic properties of flavonoids also encounter diabetic related complications. This review article has designed to shed light on the anti-diabetic potential of flavonoids, contribution of oxidative stress, evidence of efficacy in clinical, cellular and animal studies and nano-delivery approaches to enhance their therapeutic efficacy. This article might give some new insights for therapeutic intervention against T2DM in near future.

Search for Natural Compounds That Increase Apolipoprotein A-I Transcription in HepG2 Cells: Specific Attention for BRD4 Inhibitors

Although increasing apolipoprotein A‐I (apoA‐I) might lower the cardiovascular disease risk, knowledge on natural compounds that elevate apoA‐I transcription is limited. Therefore, the aim of this study was to discover natural compounds that increase apoA‐I transcription in HepG2 cells. Since BRD4 inhibition is known to elevate apoA‐I transcription, we focused on natural BRD4 inhibitors. For this, the literature was screened for compounds that might increase apoA‐I and or inhibit BRD4. This resulted in list A, (apoA‐I increasers with unknown BRD4 inhibitor capacity), list B (known BRD4 inhibitors that increase apoA‐I), and list C (BRD4 inhibitors with unknown effect on apoA‐I). These compounds were compared with the compounds in two natural compound databases. This resulted in (1) a common substructure (ethyl‐benzene) in 60% of selected BRD4‐inhibitors, and (2) four compounds that increased ApoA‐I: hesperetin, equilenin, 9(S)‐HOTrE, and cymarin. Whether these increases are regulated via BRD4 inhibition and the ethyl‐benzene structure inhibits BRD4 requires further study.

The pharmacokinetics of flavanones

The intake of flavanones, the predominant flavonoid in the Citrus genus in human diets is variable but considerable. It is thus unsurprising that they have attracted interest for their claimed positive effects on health. However, to substantiate any purported impact on health and decipher the underlying mechanism(s), knowledge of pharmacokinetics is crucial. The aim of this article is to review currently known aspects of the fate of flavanones in the organism including absorption, metabolism, distribution, and excretion as well as possible kinetic interactions with clinically used drugs. There are three principal keynotes: (1) The level of parent flavanones in plasma is negligible. The major reason for this is that although flavanones are absorbed into enterocytes after oral intake, they are rapidly metabolized, in particular, into conjugates, sulfates and glucuronides, which are the major forms circulating in plasma. (2) A large fraction reaches the colon where it is efficiently metabolized into small absorbable phenolics. (3) The form (aglycone vs. glycoside) and species (e.g. human vs. rat) have important impact. In conclusion, knowledge of the pharmacokinetics of flavanones, in particular of metabolites, their achievable plasma concentration and half-lives, should be borne in mind when their biological effects are investigated.

Absorption and Metabolic Behavior of Hesperidin (Rutinosylated Hesperetin) after Single Oral Administration to Sprague-Dawley Rats

We investigated the absorption and metabolic behavior of hesperidin (hesperetin-7-O-rutinoside) in the blood system of Sprague-Dawley rats by liquid chromatography- and matrix-assisted laser desorption ionization mass spectrometries (LC-MS and MALDI-MS). After a single oral administration of hesperidin (10 mg/kg), which was expected to be absorbed in its degraded hesperetin form, we detected intact hesperidin in the portal vein blood (t_max, 2 h) for the first time. We successfully detected glucuronized hesperidin in the circulating bloodstream, while intact hesperidin had disappeared. Further MS analyses revealed that homoeriodictyol and eriodictyol conjugates were detected in both portal and circulating blood systems. This indicated that hesperidin and/or hesperetin are susceptible to methylation and demethylation during the intestinal membrane transport process. Sulfated and glucuronized metabolites were also detected in both blood systems. In conclusion, hesperidin can enter into the circulating bloodstream in its conjugated forms, together with the conjugated forms of hesperetin, homoeriodictyol, and/or eriodictyol.

Enhanced water solubility, antioxidant activity, and oral absorption of hesperetin by D-α-tocopheryl polyethylene glycol 1000 succinate and phosphatidylcholine

Hesperetin, an abundant bioactive component of citrus fruits, is poorly water-soluble, resulting in low oral bioavailability. We developed new formulations to improve the water solubility, antioxidant activity, and oral absorption of hesperetin. Two nano-based formulations were developed, namely hesperetin-TPGS (D-α-tocopheryl polyethylene glycol 1000 succinate) micelles and hesperetin-phosphatidylcholine (PC) complexes. These two formulations were prepared by a simple technique called solvent dispersion, using US Food and Drug Administration (FDA)-approved excipients for drugs. Differential scanning calorimetry (DSC) and dynamic light scattering (DLS) were used to characterize the formulations' physical properties. Cytotoxicity analysis, cellular antioxidant activity assay, and a pharmacokinetic study were performed to evaluate the biological properties of these two formulations. The final weight ratios of both hesperetin to TPGS and hesperetin to PC were 1:12 based on their water solubility, which increased to 21.5- and 20.7-fold, respectively. The hesperetin-TPGS micelles had a small particle size of 26.19 nm, whereas the hesperetin-PC complexes exhibited a larger particle size of 219.15 nm. In addition, the cellular antioxidant activity assay indicated that both hesperetin-TPGS micelles and hesperetin-PC complexes increased the antioxidant activity of hesperetin to 4.2- and 3.9-fold, respectively. Importantly, the in vivo oral absorption study on rats indicated that the micelles and complexes significantly increased the peak plasma concentration (C_max) from 2.64 μg/mL to 20.67 and 33.09 μg/mL and also increased the area under the concentration-time curve of hesperetin after oral administration to 16.2- and 18.0-fold, respectively. The micelles and complexes increased the solubility and remarkably improved the in vitro antioxidant activity and in vivo oral absorption of hesperetin, indicating these formulations' potential applications in drugs and healthcare products.

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.

Hesperetin, a citrus flavonoid, attenuates testicular damage in diabetic rats via inhibition of oxidative stress, inflammation, and apoptosis

AIM

This study was designed to assess the beneficial effect of hesperetin on diabetes-associated testicular injury in the rat.

MAIN METHODS

Oral treatment with hesperetin started 10 days after diabetes induction by streptozotocin (60 mg/kg, i.p.) for 46 days. Testicular damage was evaluated by histological evaluation of seminiferous tubules in addition to assessment of epididymal sperm count, motility, and viability. In addition, testicular biomarkers of apoptosis, inflammation, and oxidative stress were also determined.

KEY FINDINGS

Hesperetin treatment of diabetic group prevented body weight loss and reduced serum glucose in addition to improvement of serum testosterone. Additionally, hesperetin-treated diabetic group had lower levels of malondialdehyde (MDA), reactive oxygen species (ROS), protein carbonyl, DNA fragmentation, and caspase 3 activity as specific biomarkers of oxidative stress and/or apoptosis. Furthermore, hesperetin augmented testicular antioxidant system as shown by higher levels of glutathione (GSH), mitochondrial membrane potential (MMP), and ferric reducing antioxidant power (FRAP) in addition to improvement of superoxide dismutase (SOD), catalase, and glutathione peroxidase (GPx). Moreover, hesperetin administration to diabetic rats attenuated testicular indices of inflammation consisting of tumor necrosis factor α (TNFα) and interleukin 17 (IL-17) and prevented damage of seminiferous tubules as revealed by higher levels of sperm count, motility, and viability in diabetic rats.

SIGNIFICANCE

Collectively, hesperetin could alleviate testicular damage in DM, at least through inhibition of apoptosis, oxidative stress, and inflammation in addition to its up-regulation of endogenous enzymatic and non-enzymatic antioxidants.

Prenylation enhances the biological activity of dietary flavonoids by altering their bioavailability

Flavonoids are distributed across the plant kingdom and have attracted substantial attention owing to their potential benefits for human health. Several studies have demonstrated that flavonoids prenylation enhances various biological activities, suggesting an attractive tool for developing functional foods. This review provides an overview of the current knowledge on how prenylation influences the biological activity and bioavailability of flavonoids. The enhancement effect of prenylation on the biological activities of dietary flavonoids in mammals was demonstrated by comparing the effect of 8-prenyl naringenin (8PN) with that of parent naringenin in the prevention of disuse muscle atrophy in mice. This enhancement results from higher muscular accumulation of 8PN than naringenin. As to bioavailability, despite the lower absorption of 8-prenyl quercetin (8PQ) compared with quercetin, higher 8PQ accumulation was found in the liver and kidney. These data imply that prenylation interferes with the elimination of flavonoids from tissues.

A fast screening model for drug permeability assessment based on native small intestinal extracellular matrix

The Caco-2 cell monolayer model is widely utilized to predict drug permeability across human intestinal epithelial cells. However, at least 21 days is required for the formation and maturation of a well-tight Caco-2 cell monolayer, thereby restricting the throughput of the screening model during drug discovery. To address this challenge, a fast (7 days), and more physiologically relevant screening model integrating both the Caco-2 cell model and a small intestinal submucosa (SIS) hydrogel was developed in this study. The 7 day model exhibited desirable phenotype and functional similarity to the conventional 21 day Caco-2 model with respect to paracellular resistance, alkaline phosphatase (ALP) activities, and the mRNA expression level of three transporters (PEPT1, OATP1A2, and P-gp) as well as their mediated influx or efflux. Besides, the increased gene expression of two excretive transporters (BCRP, MRP2) and their enhanced functionality were observed in the current fast model compared to the traditional 21 day model. More importantly, a strong correlation (r² = 0.9458) was obtained between the absorptive P_app values of 19 model compounds in the 7 day model and those in the conventional 21 day model. These results revealed the pivotal role of the native extracellular matrix (SIS) in facilitating the differentiation of Caco-2 cells, leading to the reconstruction of the accelerated 7 day model, which presents a promising tool for screening drug permeability in future drug discovery.

Application of a native decellularized small intestinal extracellular matrix for the construction of a fast screening model for drug absorption evaluation.

Glucuronidation: driving factors and their impact on glucuronide disposition

Glucuronidation is a well-recognized phase II metabolic pathway for a variety of chemicals including drugs and endogenous substances. Although it is usually the secondary metabolic pathway for a compound preceded by phase I hydroxylation, glucuronidation alone could serve as the dominant metabolic pathway for many compounds, including some with high aqueous solubility. Glucuronidation involves the metabolism of parent compound by UDP-glucuronosyltransferases (UGTs) into hydrophilic and negatively charged glucuronides that cannot exit the cell without the aid of efflux transporters. Therefore, elimination of parent compound via glucuronidation in a metabolic active cell is controlled by two driving forces: the formation of glucuronides by UGT enzymes and the (polarized) excretion of these glucuronides by efflux transporters located on the cell surfaces in various drug disposition organs. Contrary to the common assumption that the glucuronides reaching the systemic circulation were destined for urinary excretion, recent evidences suggest that hepatocytes are capable of highly efficient biliary clearance of the gut-generated glucuronides. Furthermore, the biliary- and enteric-eliminated glucuronides participate into recycling schemes involving intestinal microbes, which often prolong their local and systemic exposure, albeit at low systemic concentrations. Taken together, these recent research advances indicate that although UGT determines the rate and extent of glucuronide generation, the efflux and uptake transporters determine the distribution of these glucuronides into blood and then to various organs for elimination. Recycling schemes impact the apparent plasma half-life of parent compounds and their glucuronides that reach intestinal lumen, in addition to prolonging their gut and colon exposure.

Regioselective Glucuronidation of Diosmetin and Chrysoeriol by the Interplay of Glucuronidation and Transport in UGT1A9-Overexpressing HeLa Cells

This study aimed to determine the reaction kinetics of the regioselective glucuronidation of diosmetin and chrysoeriol, two important methylated metabolites of luteolin, by human liver microsomes (HLMs) and uridine-5′-diphosphate glucuronosyltransferase (UGTs) enzymes. This study also investigated the effects of breast cancer resistance protein (BCRP) on the efflux of diosmetin and chrysoeriol glucuronides in HeLa cells overexpressing UGT1A9 (HeLa—UGT1A9). After incubation with HLMs in the presence of UDP-glucuronic acid, diosmetin and chrysoeriol gained two glucuronides each, and the OH—in each B ring of diosmetin and chrysoeriol was the preferable site for glucuronidation. Screening assays with 12 human expressed UGT enzymes and chemical-inhibition assays demonstrated that glucuronide formation was almost exclusively catalyzed by UGT1A1, UGT1A6, and UGT1A9. Importantly, in HeLa—UGT1A9, Ko143 significantly inhibited the efflux of diosmetin and chrysoeriol glucuronides and increased their intracellular levels in a dose-dependent manner. This observation suggested that BCRP-mediated excretion was the predominant pathway for diosmetin and chrysoeriol disposition. In conclusion, UGT1A1, UGT1A6, and UGT1A9 were the chief contributors to the regioselective glucuronidation of diosmetin and chrysoeriol in the liver. Moreover, cellular glucuronidation was significantly altered by inhibiting BCRP, revealing a notable interplay between glucuronidation and efflux transport. Diosmetin and chrysoeriol possibly have different effects on anti-cancer due to the difference of UGT isoforms in different cancer cells.

Challenges and Opportunities with Predicting in Vivo Phase II Metabolism via Glucuronidation from in Vitro Data

Glucuronidation is the most important phase II metabolic pathway which is responsible for the clearance of many endogenous and exogenous compounds. To better understand the elimination process for compounds undergoing glucuronidation and identify compounds with desirable in vivo pharmacokinetic properties, many efforts have been made to predict in vivo glucuronidation using in vitro data. In this article, we reviewed typical approaches used in previous predictions. The problems and challenges in prediction of glucuronidation were discussed. Besides that different incubation conditions can affect the prediction accuracy, other factors including efflux / uptake transporters, enterohepatic recycling, and deglucuronidation reactions also contribute to the disposition of glucuronides and make the prediction more difficult. PBPK modeling, which can describe more complicated process in vivo, is a promising prediction strategy which may greatly improve the prediction of glucuronidation and potential DDIs involving glucuronidation. Based on previous studies, we proposed a transport-glucuronidation classification system, which was built based on the kinetics of both glucuronidation and transport of the glucuronide. This system could be a very useful tool to achieve better in vivo predictions.

Chronic exposure to short-chain fatty acids modulates transport and metabolism of microbiome-derived phenolics in human intestinal cells

Dietary fiber-derived short-chain fatty acids (SCFA) and phenolics produced by the gut microbiome have multiple effects on health. We have tested the hypothesis that long-term exposure to physiological concentrations of SCFA can affect the transport and metabolism of (poly)phenols by the intestinal epithelium using the Caco-2 cell model. Metabolites and conjugates of hesperetin (HT) and ferulic acid (FA), gut-derived from dietary hesperidin and chlorogenic acid, respectively, were quantified by LC-MS with authentic standards following transport across differentiated cell monolayers. Changes in metabolite levels were correlated with effects on mRNA and protein expression of key enzymes and transporters. Propionate and butyrate increased both FA transport and rate of appearance of FA glucuronide apically and basolaterally, linked to an induction of MCT1. Propionate was the only SCFA that augmented the rate of formation of basolateral FA sulfate conjugates, possibly via basolateral transporter up-regulation. In addition, propionate enhanced the formation of HT glucuronide conjugates and increased HT sulfate efflux toward the basolateral compartment. Acetate treatment amplified transepithelial transport of FA in the apical to basolateral direction, associated with lower levels of MCT1 protein expression. Metabolism and transport of both HT and FA were curtailed by the organic acid lactate owing to a reduction of UGT1A1 protein levels. Our data indicate a direct interaction between microbiota-derived metabolites of (poly)phenols and SCFA through modulation of transporters and conjugating enzymes and increase our understanding of how dietary fiber, via the microbiome, may affect and enhance uptake of bioactive molecules.

Intestinal transport of HDND-7, a novel hesperetin derivative, in in vitro MDCK cell and in situ single-pass intestinal perfusion models

1. Hesperetin (HDND) possesses extensive bioactivities, however, its poor solubility and low bioavailability limit its application. HDND-7, a derivative of HDND, has better solubility and high bioavailability. In this study, we investigated the intestinal absorption mechanisms of HDND-7. 2. MDCK cells were used to examine the transport mechanisms of HDND-7 in vitro, and a rat in situ intestinal perfusion model was used to characterize the absorption of HDND-7. The concentration of HDND-7 was determined by HPLC. 3. In MDCK cells, HDND-7 was effectively absorbed in a concentration-dependent manner in both directions. Moreover, HDND-7 showed pH-dependent and TEER-independent transport in both directions. The transport of HDND-7 was significantly reduced at 4 °C or in the presence of NaN3. Furthermore, the efflux of HDND-7 was apparently reduced in the presence of MRP2 inhibitors MK-571 or probenecid. However, P-gp inhibitor verapamil had no effect on the transport of HDND-7. The in situ intestinal perfusion study indicated HDND-7 was well-absorbed in four intestinal segments. Furthermore, MRP2 inhibitors may slightly increase the absorption of HDND-7 in jejunum. 4. In summary, all results indicated that HDND-7 might be absorbed mainly by passive diffusion via transcellular pathway, MRP2 but P-gp may participate in the efflux of HDND-7.

Mechanistic studies of the transport of peimine in the Caco-2 cell model

Fritillaria thunbergii Miq. has been widely used in traditional Chinese medicine for its expectorant, antitussive, antiinflammatory and analgesic properties. Moreover, modern pharmacological studies have demonstrated that F. thunbergii Miq. has efficacy in the treatment of leukemia and cancers of the liver and cervix. Although the alkaloid, peimine, is largely responsible for these pharmacological effects, it has very low oral bioavailability. The aim of this study was to investigate the intestinal absorption of peimine in Caco-2 cell monolayers. Having demonstrated that peimine is non-toxic to Caco-2 cells at concentrations <200 μmol/L, the effect of peimine concentration, pH, temperature, efflux transport protein inhibitors and EDTA-Na₂ on peimine transport were studied. The results show that peimine transport is concentration-dependent; that at pH 6.0 and 7.4, the P_app(AP-BL) of peimine is not significantly different but the P_app(BL-AP)) is; that both P_app(AP-BL) and P_app(BL-AP) at 4 °C are significantly higher than their corresponding values at 37 °C; that the P-glycoprotein (P-gp) inhibitors, verapamil and cyclosporin A, increase absorption of peimine; and that EDTA-Na₂ has no discernible effect. In summary, the results demonstrate that the intestinal absorption of peimine across Caco-2 cell monolayers involves active transport and that peimine is a substrate of P-gp.

Co-delivery of hesperetin enhanced bicalutamide induced apoptosis by exploiting mitochondrial membrane potential via polymeric nanoparticles in a PC-3 cell line

In this research, we reported the co-delivery of anti-androgen drug Bicalutamide with Hesperetin in chitosan coated polycaprolactone nanoparticles to increase their therapeutic efficacy against an androgen independent prostate cancer cell lines.

Hesperetin and its sulfate and glucuronide metabolites inhibit TNF-α induced human aortic endothelial cell migration and decrease plasminogen activator inhibitor-1 (PAI-1) levels

Hesperetin and its derived metabolites, at physiologically relevant concentrations, significantly attenuated TNF-α-induced cell migration.