Flavonoids: a class of modulators with bifunctional interactions at vicinal ATP- and steroid-binding sites on mouse P-glycoprotein

The plant matrix of Artemisia annua L. for the treatment of malaria: Pharmacodynamic and pharmacokinetic studies

Artemisinin-based combination therapies (ACTs) constitute the principal strategy for combating malaria in contemporary times, and research into the multifaceted components of Artemisia annua L. (A. annua) has garnered widespread interest among scientists. The aim of this study was to prepare A. annua extracts (nACTs) and to explore whether nACTs have higher bioavailability and efficacy than artemisinin (ART) alone due to its multiple bioactive components. Initially, the in vivo antimalarial activity of nACTs was evaluated by two murine malaria models. The results revealed that the antimalarial effect of nACTs was about 10-fold higher than that of ART alone when administered at the same dosage of ART. Then, we analyzed the pharmacokinetic characteristics of nACTs in rat plasma. Remarkably, nACTs exhibited significantly enhanced oral bioavailability, longer half-life as well as extended mean retention time in rats. In addition, the impact of nACTs on P-glycoprotein (P-gp) was evaluated using the Caco-2 cell line. The results showed that both ART and nACTs reduced the efflux rate of the P-gp substrate rhodamine 123 (R123) and induced the expression of P-gp in Caco-2 cells over a range of concentrations. nACTs had certain components-deoxyartemisinin (DEART), artemisinic acid (AA), and dihydroartemisinic acid (DHAA)-that inhibited the efflux and translocation of P-gp and facilitated the reduction of ART efflux. In conclusion, A. annua extracts significantly improved the antimalarial efficacy and bioavailability compared with ART.

A Molecular Dynamic Simulation, Structural Analysis, and Ex Vivo Insights into the P-glycoprotein Mediated Interactions of Dietary Polyphenols with Cyclin-dependent Kinase Inhibitors: A Potential Strategy to Counteract Drug Efflux

INTRODUCTION

P-glycoprotein, an ATP-dependent efflux transporter, plays a crucial role in eliminating cellular toxins and affects the intracellular concentration and bioavailability of CDK 4/6 inhibitors. Moreover, dietary flavonoids are natural bio-enhancers that can effectively inhibit the efflux function of these transporters. Therefore, this study aimed to assess the impact of dietary polyphenols on the inhibition of P-glycoprotein and the subsequent efflux of CDK inhibitors palbociclib and ribociclib.

METHODS

A molecular docking approach was implemented to evaluate the binding interaction characteristics of CDK4/6 inhibitors in the presence of dietary polyphenols at the ATP binding site. Furthermore, the stability of the complexes was evaluated in two conformations of P-glycoprotein, followed by an ex vivo everted gut sac experiment.

RESULTS

The findings demonstrated that the binding of curcumin and quercetin with high affinity (-51.63 and -47.16 Kcal/mol) to ATP binding sites of P-glycoprotein-palbociclib and ribociclib inward conformation complexes resulted in good stability of complex and minimal fluctuation throughout the course of the simulation. It was evident from the everted gut sac ex vivo study that the presence of 100 μM of curcumin resulted in an increase of 1.77 and 4.20-fold in the intestinal transit of palbociclib and ribociclib, respectively.

CONCLUSION

The study emphasizes the significance of curcumin and quercetin as inhibitors of P-glycoprotein, demonstrating their potential to decrease the efflux of palbociclib and ribociclib, consequently contributing to their bioavailability enhancement.

Exploring flavonoids as potent SLC46A3 inhibitors: Insights from the structural characteristics of flavonoid-SLC46A3 interactions

SLC46A3, a transporter for lysosomal steroid conjugates and bile acids, plays a pivotal role in the pharmacological effects of noncleavable antibody-drug conjugates using maytansine as a payload. SLC46A3 may exert negative effects on various phenomena, including copper homeostasis, mitochondrial function in the liver, and the uptake of lipid-based nanoparticles (NPs) in tumor cells. Consequently, inhibiting SLC46A3 may be a promising strategy for treating hepatic disease or enhancing lipid NP delivery to tumor cells, although the underlying mechanisms remain unknown. This study investigates flavonoids, the largest subgroup of polyphenols characterized by a simple C6-C3-C6 structure, as potential SLC46A3 inhibitors and provides insights into the structural requirements for flavonoid-SLC46A3 interactions. Screening revealed several flavonoids, including dihydrochalcones, flavonols, isoflavones, flavanones, and flavones, as effective inhibitors of 5-carboxyfluorescein (5-CF) uptake in MDCKII (Mardin-Darby canine kidney type II) cells stably expressing a mutant SLC46A3 localized to the plasma membrane. Notably, apigenin and luteolin exhibited marked 5-CF uptake inhibition, with IC50 values of 10.8 and 8.7 µM, respectively. Additionally, 4',7-dihydroxyflavone significantly inhibited 5-CF uptake, exhibiting an IC50 value of 9.3 µM, whereas acacetin and genkwanin possessing methoxy group substitutions for the hydroxy group at the 4'- or 7-position of apigenin, respectively, did not affect the uptake. Luteolin's inhibition mechanism was found to be of a mixed type involving increased Km and decreased Vmax. These findings emphasize the importance of hydroxy groups at 4'- and 7-positions in flavone-SLC46A3 interactions.

Medicinal plants as a potential resource for the discovery of novel structures towards cancer drug resistance treatment

Despite extensive research in chemotherapy, global cancer concerns persist, exacerbated by the challenge of drug resistance, which imposes economic and medical burdens. Natural compounds, particularly secondary metabolites from medicinal plants, present promising avenues for overcoming cancer drug resistance due to their diverse structures and essential pharmacological effects. This review provides a comprehensive exploration of cancer cell resistance mechanisms and target actions for reversing resistance and highlights the in vitro and in vivo efficacy of noteworthy alkaloids, flavonoids, and other compounds, emphasizing their potential as therapeutic agents. The molecular properties supporting ligand interactions are thoroughly examined, providing a robust theoretical foundation. The review concludes by discussing methods including quantitative structure-activity relationships and molecular docking, offering insights into screening potential candidates. Current trends in clinical treatment, contributing to a holistic understanding of the multifaceted approaches to address cancer drug resistance are also outlined.

Anti-bacterial, anti-biofilm and anti-quorum sensing activities of honey: A review

ETHNOPHARMACOLOGICAL RELEVANCE

Man has used honey to treat diseases since ancient times, perhaps even before the history of medicine itself. Several civilizations have utilized natural honey as a functional and therapeutic food to ward off infections. Recently, researchers worldwide have been focusing on the antibacterial effects of natural honey against antibiotic-resistant bacteria.

AIM OF THE STUDY

This review aims to summarize research on the use of honey properties and constituents with their anti-bacterial, anti-biofilm, and anti-quorum sensing mechanisms of action. Further, honey's bacterial products, including probiotic organisms and antibacterial agents which are produced to curb the growth of other competitor microorganisms is addressed.

MATERIALS AND METHODS

In this review, we have provided a comprehensive overview of the antibacterial, anti-biofilm, and anti-quorum sensing activities of honey and their mechanisms of action. Furthermore, the review addressed the effects of antibacterial agents of honey from bacterial origin. Relevant information on the antibacterial activity of honey was obtained from scientific online databases such as Web of Science, Google Scholar, ScienceDirect, and PubMed.

RESULTS

Honey's antibacterial, anti-biofilm, and anti-quorum sensing activities are mostly attributed to four key components: hydrogen peroxide, methylglyoxal, bee defensin-1, and phenolic compounds. The performance of bacteria can be altered by honey components, which impact their cell cycle and cell morphology. To the best of our knowledge, this is the first review that specifically summarizes every phenolic compound identified in honey along with their potential antibacterial mechanisms of action. Furthermore, certain strains of beneficial lactic acid bacteria such as Bifidobacterium, Fructobacillus, and Lactobacillaceae, as well as Bacillus species can survive and even grow in honey, making it a potential delivery system for these agents.

CONCLUSION

Honey could be regarded as one of the best complementary and alternative medicines. The data presented in this review will enhance our knowledge of some of honey's therapeutic properties as well as its antibacterial activities.

Total flavonoids extracted from Penthorum chinense Pursh mitigates CCl4-induced hepatic fibrosis in rats via inactivation of TLR4-MyD88-mediated NF-κB pathways and regulation of liver metabolism

Background: Penthorum chinense Pursh (PCP) is widely utilized in China to treat a variety of liver diseases. It has been shown that flavonoids inhibit inflammation and have the potential to attenuate tissue damage and fibrosis. However, the mechanisms underlying how total flavonoids isolated from PCP (TFPCP) exert their anti-fibrotic effects remain unclear. Methods: The chemical composition of TFPCP was determined using UHPLC-Q-Orbitrap HRMS. Subsequently, rats were randomly assigned to a control group (Control), a carbon tetrachloride (CCl4)-induced hepatic fibrosis model group (Model), a positive control group [0.2 mg/(kg∙day)] of Colchicine), and three TFPCP treatment groups [50, 100, and 150 mg/(kg∙day)]. All substances were administered by gavage and treatments lasted for 9 weeks. Simultaneously, rats were intraperitoneally injected with 10%-20% CCl4 for 9 weeks to induce liver fibrosis. At the end of the experiment, the liver ultrasound, liver histomorphological, biochemical indicators, and inflammatory cytokine levels were tested respectively. The underlying mechanisms were assessed using Western blot, immunohistochemistry, immunofluorescence, RT-qPCR, and metabolomics. Results: Fourteen flavonoids were identified in TFPCP. Compared with control animals, CCl4-treated rats demonstrated obvious liver injury and fibrosis, manifested as increases in gray values, distal diameter of portal vein (DDPV) and a decrease in blood flow velocity (VPV) in the ultrasound analysis; increased biochemical index values (serum levels of ALT, AST, TBIL, and ALP); marked increases in the contents of fibrotic markers (PC III, COL4, LN, HA) and inflammatory factors (serum TNF-α, IL-6, and IL-1β); and significant pathological changes. However, compared with the Model group, the ultrasound parameters were significantly improved and the serum levels of inflammatory cytokines were reduced in the TFPCP group. In contrast, the expression of TGF-β1, TLR4, and MyD88, as well as the p-P65/P65 and p-IκBα/IκBα ratios, were considerably reduced following TFPCP treatment. In addition, we identified 32 metabolites exhibiting differential abundance in the Model group. Interestingly, TFPCP treatment resulted in the restoration of the levels of 20 of these metabolites. Conclusion: Our findings indicated that TFPCP can ameliorate hepatic fibrosis by improving liver function and morphology via the inactivation of the TLR4/MyD88-mediated NF-κB pathway and the regulation of liver metabolism.

Flavonoids as P-glycoprotein inhibitors for multidrug resistance in cancer: an in-silico approach

Cancer has become a leading cause of mortality due to non-communicable diseases after cardiovascular disease worldwide and is increasing day by day at a daunting pace. According to an estimate by 2040 there will be 28.4 million cancer cases. Occurrence of multidrug resistance has further worsened the scenario of available cancer treatment. Among different mechanisms of multidrug resistance efflux of xenobiotics by ABC transporter is of prime importance. P-glycoprotein (P-gp) is the major factor behind occurrence of multidrug resistance due to its wide distribution and invariably big binding cavity. Various generations of chemical inhibitors for P-gp have been designed and tested are not devoid of major side effects. Thus, in present study flavonoids a major class of natural compounds was virtually screened in order to find molecules which can be used as selective P-gp inhibitors to be used along with chemotherapeutics. After screening 4275 molecules from different classes of flavonoids i.e. flavan, flavanol, flavonone, flavone, anthocyanins, and isoflavone, through Glide docking top ten hit molecules were selected based on their binding affinity, binding energy calculation and pharmacokinetic properties. All the hit molecules were found to have docking score within the range of -11.202 to -9.699 kcal/mol showing very strong interaction with the amino acid residues of binding pocket. Whereas, dock score of standard P-gp inhibitor verapamil was -4.984 kcal/mol. The ligand and protein complex were found to be quite stable while run through molecular dynamics simulations.Communicated by Ramaswamy H. Sarma.

ATP modulation of osmotically activated anionic current in the membrane of Phycomyces blakesleeanus sporangiophore

Ion channels are vital components of filamentous fungi signaling in communication with their environment. We exploited the ability of the apical region of growing sporangiophores of Phycomyces blakesleeanus to form membrane-enveloped cytoplasmic droplets (CDs), to examine ion currents in the filamentous fungi native plasma membrane. In hypoosmotic conditions, the dominant current in the CDs is ORIC, an osmotically activated, anionic, outwardly rectified, fast inactivating instantaneous current that we have previously characterized. Here, we examined the effect of ATP on ORIC. We show that CDs contain active mitochondria, and that respiration inhibition by azide accelerates ORIC inactivation. ATP, added intracellularly, reduced ORIC run-down and shifted the voltage dependence of inactivation toward depolarized potentials, in a manner that did not require hydrolysis. Notably, ATP led to slowing down of ORIC inactivation, as evidenced by an increased time constant of inactivation, τ_in, and slower decline of τ_in during prolonged recordings. Flavonoids (genistein and quercetin) had the effect on ORIC opposite to ATP, acting as current inhibitors, possibly by disrupting the stabilizing effect of ATP on ORIC. The integration of osmotic sensing with ATP dependence of the anionic current, typical of vertebrate cells, is described here for the first time in filamentous fungi.

Probing the Allosteric Modulation of P-Glycoprotein: A Medicinal Chemistry Approach Toward the Identification of Noncompetitive P-Gp Inhibitors

A medicinal chemistry approach combining in silico and in vitro methodologies was performed aiming at identifying and characterizing putative allosteric drug-binding sites (aDBSs) at the interface of the transmembrane- and nucleotide-binding domains (TMD-NBD) of P-glycoprotein. Two aDBSs were identified, one in TMD1/NBD1 and another one in TMD2/NBD2, by means of in silico fragment-based molecular dynamics and characterized in terms of size, polarity, and lining residues. From a small library of thioxanthone and flavanone derivatives, experimentally described to bind at the TMD-NBD interfaces, several compounds were identified to be able to decrease the verapamil-stimulated ATPase activity. An IC₅₀ of 81 ± 6.6 μM is reported for a flavanone derivative in the ATPase assays, providing evidence for an allosteric efflux modulation in P-glycoprotein. Molecular docking and molecular dynamics gave additional insights on the binding mode on how flavanone derivatives may act as allosteric inhibitors.

Computational binding affinity and molecular dynamic characterization of annonaceous acetogenins at nucleotide binding domain (NBD) of multi-drug resistance ATP-binding cassette sub-family B member 1 (ABCB1)

Multi drug resistance (MDR) in tumor might be caused leading to the overexpression of transporters, such as ATP-binding cassette sub-family B member 1 (ABCB1). A combination of non-toxic and potent ABC inhibitors along with conventional anti-cancer drugs is needed to reverse MDR in tumors. A variety of phytochemicals have been previously shown to reverse MDR. Annonaceous acetogenins (AAs) with C₃₅/C₃₇ long-chain fatty acids were reported for their anti-tumor activity, however, their effect on reversing MDR is not yet investigated. We aimed to investigate some selective AAs against the B1 subtype of ABC transporter using computational studies. Various modules of Maestro software were utilized for our in-silico analysis. Few well-characterized AAs were screened for their drug-likeness properties and tested for binding affinity at ATP and drug binding sites of ABCB1 through molecular docking. The stability of the ligand-protein complex (lowest docking score) was then determined by a molecular dynamic (MD) simulation study. Out of 24 AAs, Annonacin A (-8.10 kcal/mol) and Annohexocin (-10.49 kcal/mol) docked with a greater binding affinity at the ATP binding site than the first-generation inhibitor of ABCB1 (Verapamil: -3.86 kcal/mol). MD simulation of Annonacin A: ABCB1 complex for 100 ns also indicated that Annonacin A would stably bind to the ATP binding site. We report that Annonacin A binds at a greater affinity with ABCB1 and might act as a potential drug lead to reverse MDR in tumor cells. Communicated by Ramaswamy H. Sarma.

The Tetrahydroisoquinoline Scaffold in ABC Transporter Inhibitors that Act as Multidrug Resistance (MDR) Reversers

BACKGROUND

The failure of anticancer chemotherapy is often due to the development of resistance to a variety of anticancer drugs. This phenomenon is called multidrug resistance (MDR) and is related to the overexpression of ABC transporters, such as P-glycoprotein, multidrug resistance- associated protein 1 and breast cancer resistance protein. Over the past few decades, several ABC protein modulators have been discovered and studied as a possible approach to evade MDR and increase the success of anticancer chemotherapy. Nevertheless, the co-administration of pump inhibitors with cytotoxic drugs, which are substrates of the transporters, does not appear to be associated with an improvement in the therapeutic efficacy of antitumor agents. However, more recently discovered MDR reversing agents, such as the two tetrahydroisoquinoline derivatives tariquidar and elacridar, are characterized by high affinity towards the ABC proteins and by reduced negative properties. Consequently, many analogs of these two derivatives have been synthesized, with the aim of optimizing their MDR reversal properties.

OBJECTIVE

This review aims to describe the MDR modulators carrying the tetraidroisoquinoline scaffold reported in the literature in the period 2009-2021, highlighting the structural characteristics that confer potency and/or selectivity towards the three ABC transport proteins.

RESULTS AND CONCLUSION

Many compounds have been synthesized in the last twelve years showing interesting properties, both in terms of potency and selectivity. Although clear structure-activity relationships can be drawn only by considering strictly related compounds, some of the compounds reviewed could be promising starting points for the design of new ABC protein inhibitors.

Methoxylated flavones with potential therapeutic and photo-protective attributes: Theoretical investigation of substitution effect

The molecular and electronic structure of parent flavone and 49 (poly)methoxylated flavones (P)MFs were studied theoretically. Selected group of flavonoids consists of compounds naturally occurring in citrus plants or synthetic derivatives of flavone. These compounds exhibit several bioactivities in vitro and in vivo and can protect plants from solar ultraviolet (UV) radiation. Substitution induced structural changes in (P)MFs were correlated with published experimental values of P-glycoprotein inhibition effect. We have demonstrated that the C5-C10 bond length of 1-benzopyran-4-one moiety represents a suitable structural descriptor for this bioactivity. Obtained linear equations for the compounds with substituted and non-substituted C3 position enable the prediction of the potential anti-cancer chemo-preventive effect of the rest of studied (P)MFs. Consequently, potentially more effective substances were suggested. Optical properties of (P)MFs and their relationship with the molecular structure was examined in detail for methanol environment, as well. The multiple linear regression model was applied to assess the correlation between experimental absorption and fluorescence wavelengths with the theoretically predicted ones. The UV photo-protective potential of studied derivatives was estimated from the calculated optical properties.

Influences of Solubility and Vehicle Carriers on Eriodictyol Pharmacokinetics in Rats

In this study, the pharmacokinetics of oral doses of eriodictyol in 1% sodium carboxymethylcellulose and in saline/PEG400/Tween80 (75/20/5, v/v/v) in rats were compared. The pharmacokinetics of eriocitrin administered as a dissolved solution in water were also characterized. Metabolites of eriodictyol and eriocitrin in whole blood consisted mainly of eriodictyol, homoeriodictyol, and hesperetin glucuronides and ring-fission metabolites. In whole blood, no free nonconjugated flavanone aglycones were detected. Significant differences were observed in the pharmacokinetics of eriodictyol administered as a suspension in 1% sodium carboxymethylcellulose versus administration as a dissolved solution in saline/PEG400/Tween80 (75/20/5, v/v/v). At a dose of 25 mg kg^-1 eriodictyol administered with 1% sodium carboxymethylcellulose, a biphasic pharmacokinetic curve was observed, while only a single concentration peak was observed following an administration of 25 mg kg^-1 eriodictyol dissolved in saline/PEG400/Tween80 (75/20/5, v/v/v). For all trials, the pharmacokinetics of eriodictyol differed from those of eriocitrin dissolved in water.

Transport and Interactions of Co-incubated Bi-functional Flavonoids through Inhibiting the Function of P-Glycoprotein (P-gp) Using KB/Multidrug-Resistant (MDR) Cells and Rat Everted Gut Sacs

This study aims to evaluate the interaction of flavonoid-flavonoid by inhibiting the function of P-glycoprotein (P-gp). The cellular uptake of seven substrates and eleven co-incubated inhibitors was measured in KB/MDR cells. The effect of galangin or morin on the absorption of silibinin or wogonin was carried out in the rat everted gut sacs. Docking was performed to evaluate the interactions between inhibitors and P-gp. Most substrates were greatly enhanced by at least five co-incubated inhibitors. Conversely, the increased uptake of substrates coincided with a decrease or without affecting the uptake of inhibitors, implying a competitive/non-competitive inhibition on P-gp. The enhancement effect by galangin or morin on the transport of silibinin or wogonin was verified in everted gut sacs. Docking explained the inhibition of flavonoids on P-gp by competitively binding to the ATP site. These results provide a strategy for increasing the absorption of flavonoids by co-administration.

Reckoning apigenin and kaempferol as a potential multi-targeted inhibitor of EGFR/HER2-MEK pathway of metastatic colorectal cancer identified using rigorous computational workflow

In the past two decades, the treatment of metastatic colorectal cancer (mCRC) has been revolutionized as multiple cytotoxic, biological, and targeted drugs are being approved. Unfortunately, tumors treated with single targeted agents or therapeutics usually develop resistance. According to pathway-oriented screens, mCRC cells evade EGFR inhibition by HER2 amplification and/or activating Kras-MEK downstream signaling. Therefore, treating mCRC patients with dual EGFR/HER2 inhibitors, MEK inhibitors, or the combination of the two drugs envisaged to prevent the resistance development which eventually improves the overall survival rate. In the present study, we aimed to screen potential phytochemical lead compounds that could multi-target EGFR, HER2, and MEK1 (Mitogen-activated protein kinase kinase) using a computer-aided drug design approach that includes molecular docking, endpoint binding free energy calculation using MM-GBSA, ADMET, and molecular dynamics (MD) simulations. Docking studies revealed that, unlike all other ligands, apigenin and kaempferol exhibit the highest docking score against all three targets. Details of ADMET analysis, MM/GBSA, and MD simulations helped us to conclusively determine apigenin and kaempferol as potentially an inhibitor of EGFR, HER2, and MEK1 apigenin and kaempferol against mCRC at a systemic level. Additionally, both apigenin and kaempferol elicited antiangiogenic properties in a dose-dependent manner. Collectively, these findings provide the rationale for drug development aimed at preventing CRC rather than intercepting resistance.

A state-of-the-art review and prospective therapeutic applications of prenyl flavonoids as chemosensitizers against antifungal multidrug resistance in Candida albicans

Multidrug resistance (MDR) in the opportunistic pathogen Candida albicans is defined as non-susceptibility to at least one agent in two or more drug classes. This phenomenon has been increasingly reported since the rise in the incidence of fungal infections in immunocompromised patients at the end of the last century. After the discovery of efflux pump overexpression as a principal mechanism causing MDR in Candida strains, drug discovery targeting fungal efflux transporters has had a growing impact. Chemosensitization aims to enhance azole intracellular concentrations through combination therapy with transporter inhibitors. Consequently, the use of drug efflux inhibitors combined with the antifungal agent will sensitize the pathogen. As a result, the use of lower drug concentrations will reduce possible adverse effects on the host. Through an extensive revision of the literature, this review aims to provide an exhaustive and critical analysis of the studies carried out in the past two decades, regarding the chemosensitization strategy to cope with multidrug resistance in C. albicans. This work provides a deep analysis of the research about the inhibition of drug-efflux membrane transporters by prenylated flavonoids and the interactions of these phytocompounds with azole antifungals as an approach to chemosensitize multidrug-resistant C. albicans strains. We highlight the importance of prenylflavonoids and their particular chemical and pharmacological characteristics that make them excellent candidates with therapeutic potential as chemosensitizers. Finally, we propose the need for further research of prenyl flavonoids as inhibitors of drug-efflux mediated fungal resistance.

The role of dietary flavonoids for modulation of ATP binding cassette transporter mediated multidrug resistance

Flavonoids are widely existing compounds with enormous pharmacological effects from food and medicine. However, the low bioavailability in intestinal absorption and metabolism limits their clinical application. Intestinal efflux ABC (ATP binding cassette) transporters, including P-glycoprotein (P-gp), breast cancer resistance protein (BCRP) and multidrug resistance-associated proteins (MRPs), act as "pumping doors" to regulate the efflux of flavonoids from intestinal epithelial cells into the intestinal cavity or the systemic circulation. The present review describes the critical effect of ABC transporters involved in the efflux of flavonoids which depend on its efflux direction. And the role of flavonoids for modulation of intestinal ABC transporters was emphasized and several examples were given. We summarized that the resistance effect of flavonoid-mediated multidrug on ABC transporters may influence the bioavailability of drugs, bioactive ingredients and/or toxic compounds upon dietary uptake. Meanwhile, flavonoids functionalized as reversing agents of the ABC transporter may be an important mechanism for unexpected food-drug, food-toxin or food-food interactions. The overview also indicates that elucidation of the action and mechanism of the intestinal metabolic enzymes-efflux transporters coupling will lay a foundation for improving the bioavailability of flavonoids <i>in vivo</i> and increasing their clinical efficacy.

The Role of Genetic Pathways in the Development of Chemoradiation Resistance in Nasopharyngeal Carcinoma (NPC) Patients

Management of nasopharyngeal carcinoma (NPC) remains elusive despite new developments and advancement that has been made in the current management approaches. A patient's survival and prognosis remain dismal especially for a late-stage disease. This is highly attribute to the chemoradiation resistance. Arrays of genes and molecular mechanisms underlie the development of chemoradiation resistance in NPC. Imperatively, unravelling the true pathogenesis of chemoradiation resistance is crucial as these significant proteins and genes can be modulated to produce an effective therapeutic target. It is pivotal to identify the chemoradiation resistance at the very beginning in order to combat the chemoradiation resistance efficiently. Intense research in the genetic ecosphere is critical, as the discovery and development of novel therapeutic targets can be used for screening, diagnosis, and treating the chemoradiation resistance aggressively. This will escalate the management trajectory of NPC patients. This article highlights the significance of genetic and molecular factors that play critical roles in the chemoradiation resistance and how these factors may be modified for next-generation targeted therapy products.

Structure-activity relationship and mechanism of flavonoids on the inhibitory activity of P-glycoprotein (P-gp)-mediated transport of rhodamine123 and daunorubicin in P-gp overexpressed human mouth epidermal carcinoma (KB/MDR) cells

This study was aimed to investigate the inhibitory activity of flavonoids on P-glycoprotein (P-gp). Effects of 39 flavonoids on the cellular uptake (CU) of rhodamine123 (Rho) and daunomycin (DNR) were investigated in both parental KB and P-gp overexpressed KB/MDR cells. The inhibition mechanism of selected flavonoids was further investigated by measuring the ATPase activity and expression level of P-gp. Twelve flavonoids improved the uptake of Rho (↑Rho_F) and nineteen flavonoids increased the uptake of DNR (↑DNR_F) in KB/MDR cells with nine flavonoids overlapped. Structure-activity relationship (SAR) indicated that 8-OCH₃, and 2'-OH have a negative effect on Rho and DNR transport. Whereas 5-OH, 5-OCH₃, 6-OH, 7-OCH₃, 3'-OH, and 4'-OH, are essential for inhibition of flavonoids on P-gp and reversing the resistance of Rho and DNR. Eleven selected flavonoids significantly induced the basal P-gp-ATPase activity but much lower than that induced by verapamil. Tangeretin, galangin, kaempferol, quercetin, and morin significantly reversed the ATPase activity stimulated by verapamil. Six of eleven flavonoids significantly decreased P-gp expression, whereas three flavonoids slightly increased P-gp expression. These results provide valuable information that flavonoids can effectively reverse multidrug resistance of P-gp-mediated transport of nutraceutical and drugs by co-administration.

Heat Stress in Broiler Chickens and the Effect of Dietary Polyphenols, with Special Reference to Willow (Salix spp.) Bark Supplements-A Review

Over the last decade, there has been a growing interest in the use of a wide range of phytoadditives to counteract the harmful effects of heat stress in poultry. Willow (Salix spp.) is a tree with a long history. Among various forms, willow bark is an important natural source of salicin, β-O-glucoside of saligenin, but also of polyphenols (flavonoids and condensed tannins) with antioxidant, antimicrobial, and anti-inflammatory activity. In light of this, the current review presents some literature data aiming to: (1) describe the relationship between heat stress and oxidative stress in broilers, (2) present or summarize literature data on the chemical composition of Salix species, (3) summarize the mechanisms of action of willow bark in heat-stressed broilers, and (4) present different biological effects of the extract of Salix species in different experimental models.

Modifications of Plasma Membrane Organization in Cancer Cells for Targeted Therapy

Modifications of the composition or organization of the cancer cell membrane seem to be a promising targeted therapy. This approach can significantly enhance drug uptake or intensify the response of cancer cells to chemotherapeutics. There are several methods enabling lipid bilayer modifications, e.g., pharmacological, physical, and mechanical. It is crucial to keep in mind the significance of drug resistance phenomenon, ion channel and specific receptor impact, and lipid bilayer organization in planning the cell membrane-targeted treatment. In this review, strategies based on cell membrane modulation or reorganization are presented as an alternative tool for future therapeutic protocols.

Surface plasmon resonance biosensor combined with lentiviral particle stabilization strategy for rapid and specific screening of P-Glycoprotein ligands

A novel surface plasmon resonance-based P-gp ligand screening system (SPR-PLSS) combined with lentiviral particle (LVP) stabilization strategy was constructed to screen out potential P-gp inhibitors from natural products. Firstly, we constructed LVPs with high and low expression levels of P-gp. The LVPs can ensure the natural conformation of P-gp based on the principle that LVPs germinated from packaging cells will contain cell membrane fragments and P-gp they carry. Then the LVPs with high P-gp expression for active channel and LVPs with low P-gp expression for reference channel were immobilized on CM5 chip respectively. The affinity detection was thus carried out with the signal reduction on the two channels. The P-gp inhibitors, Valspodar (Val) and cyclosporin (CsA), as positive compounds, were detected to characterize the chip's activity, and the K_D of Val and CsA were 14.09 μM and 16.41 μM, respectively. Forty compounds from natural product library were screened using the SPR CM5 chip, and magnolol (Mag), honokiol (Hon), and resveratrol (Res) were screened out as potential P-gp ligands, showing a significant response signal. This work presented a novel P-gp ligand screening system based on LVP-immobilized biosensor to rapidly screen out P-gp ligands from natural product library. Compared with traditional cell experiments which the screening time may take up to several days, our method only takes several hours. Furthermore, this study has also provided solid evidences to support that some complicated membrane proteins would apply to the lentivirus-based SPR screening system.

Naphthylphthalamic acid associates with and inhibits PIN auxin transporters

N-1-naphthylphthalamic acid (NPA) is a key inhibitor of directional (polar) transport of the hormone auxin in plants. For decades, it has been a pivotal tool in elucidating the unique polar auxin transport-based processes underlying plant growth and development. Its exact mode of action has long been sought after and is still being debated, with prevailing mechanistic schemes describing only indirect connections between NPA and the main transporters responsible for directional transport, namely PIN auxin exporters. Here we present data supporting a model in which NPA associates with PINs in a more direct manner than hitherto postulated. We show that NPA inhibits PIN activity in a heterologous oocyte system and that expression of NPA-sensitive PINs in plant, yeast, and oocyte membranes leads to specific saturable NPA binding. We thus propose that PINs are a bona fide NPA target. This offers a straightforward molecular basis for NPA inhibition of PIN-dependent auxin transport and a logical parsimonious explanation for the known physiological effects of NPA on plant growth, as well as an alternative hypothesis to interpret past and future results. We also introduce PIN dimerization and describe an effect of NPA on this, suggesting that NPA binding could be exploited to gain insights into structural aspects of PINs related to their transport mechanism.

Quercetin acts as a P-gp modulator via impeding signal transduction from nucleotide-binding domain to transmembrane domain

The inherent ability of the cancer cells to resist chemotherapeutic agents is a major challenge in drug discovery. Chemotherapy is one of the most widely used treatment methods for cancer, but due to multidrug resistance (MDR) development in cancer cells, the healing procedure often fails. Various factors impart cancer resistance to cells; among them, P-glycoprotein (P-gp) overexpression is directly linked to MDR in cancer cells. P-gp leads to the efflux of drug molecules to the extracellular space. Several molecules have been reported to inhibit the P-gp activity. Among them, quercetin has revealed a great potential to modulate P-gp activity. However, the mechanistic understanding of quercetin induced modulation is not entirely elucidated. In the present work, we showed that quercetin binds in the interacting region between the transmembrane domain and nucleotide-binding domain out of the three plausible binding sites of P-gp and restrict the conformational change from inward- to outward-facing conformation of P-gp. Due to the absence of the inward-facing structure of human P-gp, we first modeled an inward-facing P-gp structure. Using molecular docking, the interacting residues of P-gp were identified, and the stability and interaction dynamics of the complex were studied using molecular dynamics simulation. Our work reveals the mechanistic understanding of quercetin induced modulation of P-gp and indicates its importance in cancer treatment.Communicated by Ramaswamy H. Sarma.

Molecular interaction and cellular studies on combination photodynamic therapy with rutoside for melanoma A375 cancer cells: an in vitro study

Background

Melanoma as a type of skin cancer, is associated with a high mortality rate. Therefore, early diagnosis and efficient surgical treatment of this disease is very important. Photodynamic therapy (PDT) involves the activation of a photosensitizer by light at specific wavelength that interacts with oxygen and creates singlet oxygen molecules or reactive oxygen species (ROS), which can lead to tumor cell death. Furthermore, one of the main approches in the prevention and treatment of various cancers is plant compounds application. Phenolic compounds are essential class of natural antioxidants, which play crucial biological roles such as anticancer effects. It was previously suggested that flavonoid such as rutoside could acts as pro-oxidant or antioxidant. Hence, in this study, we aimed to investigate the effect of rutoside on the combination therapy with methylene blue (MB) assisted by photodynamic treatment (PDT) using red light source (660 nm; power density: 30 mW/cm²) on A375 human melanoma cancer cells.

Methods

For this purpose, the A375 human melanoma cancer cell lines were treated by MB-PDT and rutoside. Clonogenic cell survival, MTT assay, and cell death mechanisms were also determined after performing the treatment. Subsequently, after the rutoside treatment and photodynamic therapy (PDT), cell cycle and intracellular reactive oxygen species (ROS) generation were measured.

Results

The obtained results showed that, MB-PDT and rutoside had better cytotoxic and antiprolifrative effects on A375 melanoma cancer cells compared to each free drug, whereas the cytotoxic effect on HDF human dermal fibroblast cell was not significant. MB-PDT and rutoside combination induced apoptosis and cell cycle arrest in the human melanoma cancer cell line. Intracellular ROS increased in A375 cancer cell line after the treatment with MB-PDT and rutoside.

Conclusion

The results suggest that, MB-PDT and rutoside could be considered as novel approaches as the combination treatment of melanoma cancer.

Nitrogen-containing naringenin derivatives for reversing multidrug resistance in cancer

Naringenin (1), isolated from Euphorbia pedroi, was previously derivatized yielding compounds 2-13. In this study, aiming at expanding the pool of analogues of the flavanone core towards better multidrug resistance (MDR) reversal agents, alkylation reactions and chemical modification of the carbonyl moiety was performed (15-39). Compounds structures were assigned mainly by 1D and 2D NMR experiments. Compounds 1-39 were assessed as MDR reversers, in human ABCB1-transfected mouse T-lymphoma cells, overexpressing P-glycoprotein (P-gp). The results revealed that O-methylation at C-7, together with the introduction of nitrogen atoms and aromatic moieties at C-4 or C-4', significantly improved the activity, being compounds 27 and 37 the strongest P-gp modulators and much more active than verapamil. In combination assays, synergistic interactions of selected compounds with doxorubicin substantiated the results. While molecular docking suggested that flavanone derivatives act as competitive modulators, molecular dynamics showed that dimethylation promotes binding to a modulator-binding site. Moreover, flavanones may also interact with a vicinal ATP-binding site in both nucleotide-binding domains, hypothesizing an allosteric mode of action.

The effect of green tea catechins on breast cancer resistance protein activity and intestinal efflux of aflatoxin B1 via breast cancer resistance protein in Caco-2 cells

Aflatoxin B₁ (AFB₁), a mycotoxin produced by Aspergillus spp., was proved as one of the major causes of human hepatocellular carcinoma (HCC) when chronically consumed. An efflux of AFB₁ was reported to be associated with breast cancer resistance protein (BCRP) whose activity could also be modulated by green tea catechins. The purpose of this study was, therefore, to examine the impacts of green tea catechins on BCRP activity in Caco-2 cells by H33342 (bis-benzamide, BCRP substrate) accumulation and AFB₁ efflux. Results showed a significant decrease (p < 0.05) of AFB₁ in the efflux ratio following the incubation with Ko143, a specific BCRP inhibitor, and sodium fluoride, confirming the association of BCRP in AFB₁ efflux transport across the cells. Pre-incubation with green tea and gallate catechins (ECG and EGCG) significantly reduced the efflux ratio of AFB₁ (p < 0.05) and significantly increased the intracellular H33342 substrate (p < 0.05) in Caco-2 cells, clearly indicating the inhibitory effects of green tea and gallate catechins on BCRP function. Further study on H33342 accumulation revealed a dose-dependent increment of intracellular H33342 when co-administered with increasing concentrations of AFB₁. This result implied a possible role of AFB₁ as a BCRP competitive inhibitor. The findings from this study concluded the roles of BCRP as an efflux transporter for AFB₁ and could be modulated by the exposure of green tea catechins. Owing to a reduction of its efflux, an inhibitory effect of BCRP when pre-exposed with green tea catechins could be crucial for AFB₁ cellular accumulation.

Phytochemicals: Potential Lead Molecules for MDR Reversal

Multidrug resistance (MDR) is one of the main impediments in the treatment of cancers. MDR cancer cells are resistant to multiple anticancer drugs. One of the major mechanisms of MDR is the efflux of anticancer drugs by ABC transporters. Increased activity and overexpression of these transporters are important causes of drug efflux and, therefore, resistance to cancer chemotherapy. Overcoming MDR is a fundamental prerequisite for developing an efficient treatment of cancer. To date, various types of ABC transporter inhibitors have been employed but no effective anticancer drug is available at present, which can completely overcome MDR. Phytochemicals can reverse MDR in cancer cells via affecting the expression or activity of ABC transporters, and also through exerting synergistic interactions with anticancer drugs by addressing additional molecular targets. We have listed numerous phytochemicals which can affect the expression and activity of ABC transporters in MDR cancer cell lines. Phytochemicals in the groups of flavonoids, alkaloids, terpenes, carotenoids, stilbenoids, lignans, polyketides, and curcuminoids have been examined for MDR-reversing activity. The use of MDR-reversing phytochemicals with low toxicity to human in combination with effective anticancer agents may result in successful treatment of chemotherapy-resistant cancer. In this review, we summarize and discuss published evidence for natural products with MDR modulation abilities.

Theoretical insights on helix repacking as the origin of P-glycoprotein promiscuity

P-glycoprotein (P-gp, ABCB1) overexpression is, currently, one of the most important multidrug resistance (MDR) mechanisms in tumor cells. Thus, modulating drug efflux by P-gp has become one of the most promising approaches to overcome MDR in cancer. Yet, more insights on the molecular basis of drug specificity and efflux-related signal transmission mechanism between the transmembrane domains (TMDs) and the nucleotide binding domains (NBDs) are needed to develop molecules with higher selectivity and efficacy. Starting from a murine P-gp crystallographic structure at the inward-facing conformation (PDB ID: 4Q9H), we evaluated the structural quality of the herein generated human P-gp homology model. This initial human P-gp model, in the presence of the “linker” and inserted in a suitable lipid bilayer, was refined through molecular dynamics simulations and thoroughly validated. The best human P-gp model was further used to study the effect of four single-point mutations located at the TMDs, experimentally related with changes in substrate specificity and drug-stimulated ATPase activity. Remarkably, each P-gp mutation is able to induce transmembrane α-helices (TMHs) repacking, affecting the drug-binding pocket volume and the drug-binding sites properties (e.g. volume, shape and polarity) finally compromising drug binding at the substrate binding sites. Furthermore, intracellular coupling helices (ICH) also play an important role since changes in the TMHs rearrangement are shown to have an impact in residue interactions at the ICH-NBD interfaces, suggesting that identified TMHs repacking affect TMD-NBD contacts and interfere with signal transmission from the TMDs to the NBDs.

Curcumin effect on cancer cells' multidrug resistance: An update

Chemotherapy is one of the main methods for cancer treatment. However, despite many advances in the design of anticancer drugs, their efficiency is limited due to their high toxicity and resistance of cells to chemotherapeutic drugs. In order to improve the cancer therapy, it is essential to use the compounds that can overcome drug resistance and increase treatment efficiency. Researchers have studied the effects of natural compounds for the controlling various drug resistance mechanisms. Curcumin is a natural phenolic compound which shows potent anticancer activities in different tumors, alone or as an adjuvant with other antitumor drugs to prevent or inhibit the survival and cancer progression by various mechanisms. The role of curcumin in overcoming drug resistance was followed by reviewing different applications of curcumin in cancer therapy. Afterward, the clinical impacts of curcumin, role of curcumin in decreasing drug resistance in different cancer cells and its mechanisms were discussed. It has been demonstrated that curcumin regulates signaling pathways in cancer cells, reduces the expression of proteins related to drug resistance, and increases the performance of antitumor drugs at various levels. Curcumin reverses multidrug resistance mechanisms and increases sensitivity of resistance cells to chemotherapy. This review mainly focuses on different mechanisms of drug resistance and curcumin as a nontoxic natural substance to eliminate the effects of drug resistance through modulation and controlling cell resistance pathways and eventually suggests curcumin as a potent chemosensitizer in cancers.

Flavonoids as P-gp Inhibitors: A Systematic Review of SARs

P-glycoprotein, also known as ABCB1 in the ABC transporter family, confers the simultaneous resistance of metastatic cancer cells towards various anticancer drugs with different targets and diverse chemical structures. The exploration of safe and specific inhibitors of this pump has always been the pursuit of scientists for the past four decades. Naturally occurring flavonoids as benzopyrone derivatives were recognized as a class of nontoxic inhibitors of P-gp. The recent advent of synthetic flavonoid dimer FD18, as a potent P-gp modulator in reversing multidrug resistance both in vitro and in vivo, specifically targeted the pseudodimeric structure of the drug transporter and represented a new generation of inhibitors with high transporter binding affinity and low toxicity. This review concerned the recent updates on the structure-activity relationships of flavonoids as P-gp inhibitors, the molecular mechanisms of their action and their ability to overcome P-gp-mediated MDR in preclinical studies. It had crucial implications on the discovery of new drug candidates that modulated the efflux of ABC transporters and also provided some clues for the future development in this promising area.

Effect of piperine and quercetin alone or in combination with marbofloxacin on CYP3A37 and MDR1 mRNA expression levels in broiler chickens

After oral route of administration, drug absorption is unpredictable and is governed by various factors such as multi drug resistance-1 (MDR1) an efflux transporter and drug metabolizing enzymes (like CYP3A4, CYP3A37, CYP2D6) at intestine and liver. Naturally available phyto chemicals like piperine and quercetin as well as some floroquinolones are known to inhibit MDR1 and CYP3A37 activity and increases bioavailability of co-administered drugs. This study was carried out to investigate the effect of piperine and quercetin alone or in combination with marbofloxacin on CYP3A37 and MDR1 mRNA expression levels in liver and intestine of broiler chicken. After oral administration of piperine and quercetin for 3 consecutive days followed by with or without oral administration of marbofloxacin for 5 days, CYP3A37 and MDR1 mRNA expression levels were determined using quantitative real-time PCR. Total of 36 broiler chickens in seven individual groups were treated with different regimen and the mRNA expression levels at duodenum and liver were analyzed with apt statistical tools. After piperine and quercetin combined treatment with marbofloxacin, CYP3A37 mRNA expression levels were significantly down regulated by 20.57 (p = .034) and 25.95 (p = .003) folds; and MDR1 mRNA expression levels were also significantly down regulated by 11.33 (p = .012) and 33.59 (p = .006) folds in liver and duodenum, respectively. Down regulation of CYP3A37 and MDR1 mRNA in liver and duodenum indicate the combined pretreatment of piperine and quercetin may be useful for improving the pharmacokinetics of orally administered drugs which are substrates for CYP3A37 and MDR1.

Ficus extract-A promising agent for antimammary tumorigenesis: A review on current status and future possibilities

Pharmacological studies have shown that various species of Ficus have antiviral, antidiarrheal, antipyretic, hypolipidemic, antidiabetic, antioxidant, anticancer, antiparasitic, antiangiogenic, anti-inflammatory, antibacterial, antiplatelet, reproductive, dermatological, immunological, endocrine, and hepato and nephron protective effects. But there is no sufficient research on biomolecules present in the leaf extract of Ficus religiosa and its mechanism of action. We have previously reported that bioavailable constituents of F. religiosa leaf extract exert photosensitizing and apoptosis-inducing capability through the generation of intracellular reactive oxygen species on breast cancer cells. In this review, we have evaluated the expression of checkpoint proteins of G1/S and sub G0 phase with wet lab data and also have done a data mining of other research for other potential mechanistic action of the F. religiosa leaf extract.

Effect of chrysin on the formation of N-acetyl-p-benzoquinoneimine, a toxic metabolite of paracetamol in rats and isolated rat hepatocytes

Paracetamol (N-acetyl-para amino phenol) is the most commonly used analgesic and antipyretic around the world. Its causes hepatotoxicity and nephrotoxicity at overdose or even at therapeutic doses. It is primarily metabolized by glucuronidation and sulfate conjugation. It is also metabolized by cytochrome-P450 system (CYP2E1, CYP1A2 and CYP 3A4), leading to the formation of N-acetyl-p-benzoquinoneimine (NAPQI). The present study was planned to investigate the influence of chrysin (known CYP2E1 and CYP3A4 inhibitor) on the bioactivation of paracetamol to NAPQI using rat liver microsomes in vitro and rats in vivo. Paracetamol (80 mg/kg) was administered orally without or with silymarin (100 mg/kg), a known CYP2E1 inhibitor and chrysin (100 and 200 mg/kg) to rats for 15 consecutive days. The area under the plasma concentration-time curve (AUC_0-∞) and the peak plasma concentration (C_max) of paracetamol were dose-dependently increased with chrysin (100 and 200 mg/kg) compared to paracetamol control group. On the other hand, the AUC_0-∞ and C_max of NAPQI were decreased significantly with chrysin (100 and 200 mg/kg). The elevated liver and kidney function markers were significantly reduced by chrysin and silymarin compared to paracetamol control group (P < 0.01). Histopathological studies of liver and kidney also well correlated with liver and kidney function tests. Chrysin also reduced the formation of NAPQI in the incubation samples of rat hepatocytes. The present study (both in vivo and in vitro) results revealed that chrysin might be inhibited the CYP2E1, CYP1A2 and CYP3A4-mediated metabolism of paracetamol; thereby decreased the formation of NAPQI and protected the liver and kidney.

In silico analysis of nsSNPs in ABCB1 gene affecting breast cancer associated protein P-glycoprotein (P-gp)

Breast cancer is one of the most common cancers among women and increased expression of some polymorphic genes, which is rare within families, enhances the risk of breast cancer incidence. The correct identification of the functional SNPs of such genes is important for characterizing the functional aspect of these SNPs which can be assessed by evaluating their significant influence on the structure and function of proteins. Since the presence of SNPs in these genes affects the quality of life of a breast cancer patient, thus, the associated diagnostic markers have a reliable potential for assessing the prognosis of breast cancer. ATP-binding cassette (ABC) genes have been shown to obstruct the treatment of breast cancer by providing resistance to malignant cells from anti-cancer drugs. Some allelic variants of ABCG2 and ABCB1 are also associated with occurrence of skin toxicity during the treatment of breast cancer with anti-cancer drugs. The present study has incorporated comprehensive bioinformatics analysis to explore the possible disease-associated mutations of ABCB1 gene, a gene that resulted from gene-environment interaction study, and understand their consequential effect on the structural and functional behavior of P-glycoprotein. Two gene variants (R538S and M701R) of P-glycoprotein were selected as potentially detrimental point mutations, and these variants were modeled. Molecular dynamic simulation (MDS) studies unraveled the atomic interactions and motion trajectories of the native as well as the two mutant (R538S and M701R) structures and were predicted to have a deleterious effect on breast cancer associated P-gp. Thus, the present study may broaden the way to design novel potent drugs for overcoming the problems associated with multidrug resistance (MDR) resulting from a change in protein conformation due to a mutation in ABCB1 gene.

Analysis of Fluorescence Spectra of Citrus Polymethoxylated Flavones and Their Incorporation into Mammalian Cells

Citrus polymethoxylated flavones (PMFs) influence biochemical cascades in human diseases, yet little is known about how these compounds interact with cells and how these associations influence the actions of these compounds. An innate attribute of PMFs is their ultraviolet-light-induced fluorescence, and the fluorescence spectra of 14 PMFs and 7 PMF metabolites were measured in methanol. These spectra were shown to be strongly influenced by the compounds' hydroxy and methoxy substituents. For a subset of these compounds, the fluorescence spectra were measured when bound to human carcinoma Huh7.5 cells. Emission-wavelength maxima of PMF metabolites with free hydroxyl substituents exhibited 70-80 nm red shifts when bound to the Huh7.5 cells. Notable solvent effects of water were observed for nearly all these compounds, and these influences likely reflect the effects of localized microenvironments on the resonance structures of these compounds when bound to human cells.

Simultaneous Determination of Chrysin and Tectochrysin from Alpinia oxyphylla Fruits by UPLC-MS/MS and Its Application to a Comparative Pharmacokinetic Study in Normal and Dementia Rats

A simple and rapid ultra-performance liquid chromatography⁻tandem mass spectrometry (UPLC⁻MS/MS) coupled with a one-step liquid-liquid extraction method has been developed and validated for the simultaneous determination of two flavonoids (chrysin, tectochrysin) from Alpinia oxyphylla fruits extract in rat plasma. Plasma samples were extracted with diethyl ether and separated on an ACQUITY UPLC BEH C₁₈ column (100 mm × 2.1 mm, 1.7 μm) using gradient elution consisting of 0.1% formic acid in water (A) and methanol (B). The multiple reaction monitoring (MRM) mode with electrospray ionization in the positive ion mode was used for detection. The linear range was 0.1 ng/mL to 50 ng/mL for chrysin and tectochrysin, respectively. The accuracy (relative error, RE%) ranged from -8.8% to 7.5% and the intra-day and inter-day precision were within 15% and had a mean extraction recovery rate of 80.3% to 86.7%. The validated method was applied to a comparative pharmacokinetic study after oral administration of Alpinia oxyphylla fruit ethanol extract between normal rats and dementia rats. The area under the curve (AUC) and peak plasma concentration (C_max) of the two constituents were remarkably increased in dementia rats than in normal rats.

Dietary Intake of Curcumin Improves eIF2 Signaling and Reduces Lipid Levels in the White Adipose Tissue of Obese Mice

White adipose tissue (eWAT) plays a crucial role in preventing metabolic syndrome. We aimed to investigate WAT distribution and gene expression and lipidomic profiles in epididymal WAT (eWAT) in diet-induced obese mice, reflecting a Western-style diet of humans to elucidate the bioactive properties of the dietary antioxidant curcumin in preventing lifestyle-related diseases. For 16 weeks, we fed C57BL/6J mice with a control diet, a high-fat, high-sucrose and high-cholesterol Western diet or Western diet supplemented with 0.1% (w/w) curcumin. Although the dietary intake of curcumin did not affect eWAT weight or plasma lipid levels, it reduced lipid peroxidation markers’ levels in eWAT. Curcumin accumulated in eWAT and changed gene expressions related to eukaryotic translation initiation factor 2 (eIF2) signalling. Curcumin suppressed eIF2α phosphorylation, which is induced by endoplasmic reticulum (ER) stress, macrophage accumulation and nuclear factor-κB (NF-κB) p65 and leptin expression, whereas it’s anti-inflammatory effect was inadequate to decrease TNF-α and IFN-γ levels. Lipidomic and gene expression analysis revealed that curcumin decreased some diacylglycerols (DAGs) and DAG-derived glycerophospholipids levels by suppressing the glycerol-3-phosphate acyltransferase 1 and adipose triglyceride lipase expression, which are associated with lipogenesis and lipolysis, respectively. Presumably, these intertwined effects contribute to metabolic syndrome prevention by dietary modification.

Optimizing the flavanone core toward new selective nitrogen-containing modulators of ABC transporters

Aim: Naringenin (1), isolated in large amount from the aerial parts of Euphorbia pedroi, was chemically derivatized to yield 18 imine derivatives (2–19) and three alkylated derivatives through a Mannich-type reaction (20–22) that were tested as multidrug resistance (MDR) reversers in cancer cells. Results/methodology: While hydrazone (2–4) and azine (5–13) derivatives showed an improvement in their MDR reversal activities against the breast cancer resistance protein, carbohydrazides 14–19 revealed an enhancement in MDR reversal activity toward the multidrug resistance protein 1. Conclusion: The observed activities, together with pharmacophoric analysis and molecular docking studies, identified the spatial orientation of the substituents as a key structural feature toward a possible mechanism by which naringenin derivatives may reverse MDR in cancer.

In vitro screening of dual flavonoid combinations for reversing P-glycoprotein-mediated multidrug resistance: Focus on antiepileptic drugs

The combined use of different P-glycoprotein (P-gp) inhibitors may be a relevant approach to the synergistic and safer inhibition of the P-gp-mediated drug efflux. Herein, we aimed to explore dual combinations of the flavonoids baicalein, (-)-epigallocatechin gallate, kaempferol, quercetin and silymarin to reverse the interference of P-gp on the intracellular accumulation of antiepileptic drugs (AEDs). The intracellular accumulation of rhodamine 123 (a classic P-gp substrate) and of several commonly used AEDs (carbamazepine, phenytoin, oxcarbazepine) or their metabolites (carbamazepine-10,11-epoxide and licarbazepine) was evaluated in MDCK-MDR1 cells in the presence and absence of individual flavonoids and their combinations. A selected flavonoid combination [(-)-epigallocatechin gallate/silymarin] was also evaluated in transepithelial transport experiments using licarbazepine (active metabolite of oxcarbazepine) as a model compound. Most flavonoid combinations increased rhodamine 123 intracellular uptake in a greater extent than their additive individual effects at similar concentrations. Moreover, selected (-)-epigallocatechin gallate/silymarin and kaempferol/baicalein combinations also enhanced the intracellular accumulation of all AEDs and metabolites. Overall, the combination of (-)-epigallocatechin gallate/silymarin was the most promising one. Thus, dual flavonoid combinations may be useful to overcome the P-gp-mediated efflux of AEDs and their metabolites, making their association to AED therapy a potentially valuable approach to circumvent pharmacoresistance in epilepsy.

Pharmacokinetic interaction of green tea beverage containing cyclodextrins and high concentration catechins with P-glycoprotein substrates in LLC-GA5-COL150 cells in vitro and in the small intestine of rats in vivo

OBJECTIVES

Possible interaction of green tea beverage (GT) containing cyclodextrins and high concentration catechins, a drinking water, with P-glycoprotein (P-gp) substrates was examined in vitro and in vivo.

METHODS

Effects of GT on the uptake of rhodamine 123 by LLC-GA5-COL150 cells and intestinal efflux of rhodamine 123 from blood, intestinal absorption of quinidine from ileum loop and oral absorption of digoxin were examined in rats. Effects of GT and GT components on digoxin solubility were also examined.

KEY FINDINGS

Green tea increased the uptake of rhodamine 123 by LLC-GA5-COL150 cells, suppressed the intestinal efflux of rhodamine 123 from blood and increased the absorption of quinidine in the ileum of rats. Also, GT increased the solubility of digoxin, and ingestion of GT significantly increased the oral absorption of digoxin given at a high dose in rats.

CONCLUSIONS

Green tea suppressed the P-gp-mediated efflux transport of hydrophilic compounds and increased the solubility of lipophilic compounds. Thus, GT may cause interaction with various P-gp substrates, due to the combined effects of catechins and cyclodextrins. Especially, cyclodextrin alone can cause interaction with various low-solubility compounds in vivo. In taking low-solubility drugs including low-solubility P-gp substrates, cyclodextrin-containing foods and beverages such as GT should be avoided.

A Critical View on ABC Transporters and Their Interacting Partners in Auxin Transport

Different subclasses of ATP-binding cassette (ABC) transporters have been implicated in the transport of native variants of the phytohormone auxin. Here, the putative, individual roles of key members belonging to the ABCB, ABCD and ABCG families, respectively, are highlighted and the knowledge of their assumed expression and transport routes is reviewed and compared with their mutant phenotypes. Protein-protein interactions between ABC transporters and regulatory components during auxin transport are summarized and their importance is critically discussed. There is a focus on the functional interaction between members of the ABCB family and the FKBP42, TWISTED DWARF1, acting as a chaperone during plasma membrane trafficking of ABCBs. Further, the mode and relevance of functional ABCB-PIN interactions is diagnostically re-evaluated. A new nomenclature describing precisely the most likely ABCB-PIN interaction scenarios is suggested. Finally, available tools for the detection and prediction of ABC transporter interactomes are summarized and the potential of future ABC transporter interactome maps is highlighted.

Flavonoids as modulators of metabolic enzymes and drug transporters

Flavonoids, natural compounds found in plants and in plant-derived foods and beverages, have been extensively studied with regard to their capacity to modulate metabolic enzymes and drug transporters. In vitro, flavonoids predominantly inhibit the major phase I drug-metabolizing enzyme CYP450 3A4 and the enzymes responsible for the bioactivation of procarcinogens (CYP1 enzymes) and upregulate the enzymes involved in carcinogen detoxification (UDP-glucuronosyltransferases, glutathione S-transferases (GSTs)). Flavonoids have been reported to inhibit ATP-binding cassette (ABC) transporters (multidrug resistance (MDR)-associated proteins, breast cancer-resistance protein) that contribute to the development of MDR. P-glycoprotein, an ABC transporter that limits drug bioavailability and also induces MDR, was differently modulated by flavonoids. Flavonoids and their phase II metabolites (sulfates, glucuronides) inhibit organic anion transporters involved in the tubular uptake of nephrotoxic compounds. In vivo studies have partially confirmed in vitro findings, suggesting that the mechanisms underlying the modulatory effects of flavonoids are complex and difficult to predict in vivo. Data summarized in this review strongly support the view that flavonoids are promising candidates for the enhancement of oral drug bioavailability, chemoprevention, and reversal of MDR.