A multitarget semi-synthetic derivative of the flavonoid morin with improved in vitro vasorelaxant activity: Role of CaV1.2 and KCa1.1 channels

Bioguided Identification of Polymethoxyflavones as Novel Vascular CaV1.2 Channel Blockers from Citrus Peel

The huge amount of citrus peel produced worldwide represents an economic burden for society. However, this agricultural by-product is a rich source of natural molecules, potentially endowed with interesting pharmacological activities. In this regard, we decided to investigate if the polymethoxyflavones contained in citrus peel waste could be exploited as novel vasorelaxant agents. A hydroalcoholic blond orange (Citrus sinensis) peel extract, obtained by ultrasonication, was partitioned in dichloromethane. Column chromatography allowed for the isolation of four polymethoxyflavones, namely, scutellarein tetramethyl ether, nobiletin, tangeretin, and sinensetin, identified by nuclear magnetic resonance (NMR) spectroscopy and UPLC-HRMS/MS and confirmed by multivariate curve resolution of NMR fractional spectra. The four molecules showed interesting in vitro vasorelaxant activity, at least, in part, due to the blockade of smooth muscle CaV1.2 channels. Molecular modeling and docking analysis elucidated the binding mode of the polymethoxyflavones at the homology model of the rat CaV1.2c subunit and provided the structural basis to rationalise the highest activity of scutellarein tetramethyl ether in the set and the dramatic effect of the additional methoxy group occurring in nobiletin and sinensetin. In conclusion, citrus peel can be considered a freely available, valuable source of vasoactive compounds worthy of pharmaceutical and/or nutraceutical exploitation.

Chaetomorpha linum Extract as a Source of Antimicrobial Compounds: A Circular Bioeconomy Approach

The circular bioeconomy is currently a promising model for repurposing natural sources; these sources include plants due to their abundance of bioactive compounds. This study evaluated the antimicrobial properties of a Chaetomorpha linum extract. Chaetomorpha linum is an invasive macroalga from the Orbetello Lagoon (Tuscany, Italy), which grows in nutrient-rich environments and has been forming extended mats since 2005. The biomass is mechanically harvested and treated as waste, consuming considerable manpower and financial resources. As a potential way to increase the value of such waste, this study found that C. linum extract (CLE) is a source of antimicrobial compounds. The phytochemical characterization of the extract revealed the predominant presence of palmitic acid, a fatty acid with known antimicrobial activity. Based on such findings, four bacterial species of high clinical relevance (Enterococcus faecalis, Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli) were tested, revealing a notable antibacterial activity of the extract on Enterococcus faecalis (MIC, 32 μg/mL). Computational analyses identified a potential Enterococcus faecalis molecular target for palmitic acid, offering molecular insights on the interaction. This study presents a comprehensive in vitro and in silico approach for drug and target discovery studies by repurposing C. linum as a source of antimicrobial bioactive compounds.

Exploring the chemical space around chrysin to develop novel vascular CaV1.2 channel blockers, promising vasorelaxant agents

The flavonoid chrysin is an effective vascular CaV1.2 channel blocker. The aim of this study was to explore the chemical space around chrysin to identify the structural features that can be modified to develop novel and more effective blockers. Four derivatives (Chrysin 1-4) were synthesised and a functional, electrophysiology and molecular docking approach was pursued to assess their binding mode to CaV1.2 channels and their activity in vascular preparations. Methylation of the 5- and 7-OH of the chrysin backbone caused a marked reduction of the Ca2+ antagonistic potency and efficacy. However, C-8 derivatives showed biophysical features similar to those of the parent compound and, like nicardipine, bound with high affinity to and stabilised the CaV1.2 channel in its inactivated state. The vasorelaxant effects of the four derivatives appeared vessel-specific, addressing the molecules' derivatization towards different targets. In conclusion, the scaffold of chrysin may be considered a valuable starting point for the development of innovative vascular CaV1.2 channel blockers.

Discovery of pyridoquinoxaline-based new P-gp inhibitors as coadjutant against Multi Drug Resistance in cancer

Multi-drug resistance (MDR) is a serious challenge in contemporary clinical practice and is mostly responsible for the failure of cancer medication therapies. Several experimental evidence links MDR to the overexpression of the drug efflux transporter P-gp, therefore, the discovery of novel P-glycoprotein inhibitors is required to treat or prevent MDR and to improve the absorption of chemotherapy drugs via the gastrointestinal system. In this work, we explored a series of novel pyridoquinoxaline-based derivatives designed from parental compounds, previously proved active in enhancing anticancer drugs in MDR nasopharyngeal carcinoma (KB). Among them, derivative 10d showed the most potent and selective inhibition of fluorescent dye efflux, if compared to reference compounds (MK-571, Novobiocin, Verapamil), and the highest MDR reversal activity when co-administered with the chemotherapeutic agents Vincristine and Etoposide, at non-cytotoxic concentrations. Molecular modelling predicted the two compound 10d binding mode in a ratio of 2:1 with the target protein. No cytotoxicity was observed in healthy microglia cells and off-target investigations showed the absence of CaV1.2 channel blockade. In summary, our findings indicated that 10d could potentially be a novel therapeutic coadjutant by inhibiting P-gp transport function in vitro, thereby reversing cancer multidrug resistance.

The flavonoid resokaempferol improves insulin secretion from healthy and dysfunctional pancreatic β-cells

BACKGROUND AND PURPOSE

The pharmacology of flavonoids on β-cell function is largely undefined especially in the context of defective secretion of insulin. We sought to identify flavonoids that increased the insulin-secreting function of β-cells and to explore the underlying mechanisms.

EXPERIMENTAL APPROACH

INS-1 β-cells in culture and islets of Langerhans isolated from control and diabetic male rats were used for insulin secretion experiments. Pharmacological and electrophysiological approaches were used for mechanistic studies.

KEY RESULTS

Among a set of flavonoids, exposure of INS-1 β-cells to resokaempferol (ResoK) enhanced glucose-stimulated insulin secretion and therefore we further characterised its activity and its pharmacological mechanism. ResoK glucose-dependently enhanced insulin secretion in INS-1 β-cells and pancreatic islets isolated from rats. Mechanistically, whole cell patch clamp recordings in INS-1 cells showed that ResoK rapidly and dose-dependently enhanced the L-type Ca2+ current whereas it was inactive towards T-type Ca2+ current. Accordingly, pharmacological inhibition of L-type Ca2+ current but not T-type Ca2+ current blocked the effects of ResoK on glucose-stimulated insulin secretion. ResoK was still active on dysfunctional β-cells as it ameliorated glucose-stimulated insulin secretion in glucotoxicity-induced dysfunctional INS-1 cells and in pancreatic islets isolated from diabetic rats.

CONCLUSION AND IMPLICATIONS

ResoK is a glucose-dependent activator of insulin secretion. Our results indicated that the effects of ResoK on insulin secretion involved its capacity to stimulate L-type Ca2+ currents in cultured β-cells. As ResoK was also effective on dysfunctional β-cells, our work provides a new approach to stimulating insulin secretion, using compounds based on the structure of ResoK.

HGA Triggers SAA Aggregation and Accelerates Fibril Formation in the C20/A4 Alkaptonuria Cell Model

Alkaptonuria (AKU) is a rare autosomal recessive metabolic disorder caused by mutations in the homogentisate 1,2-dioxygenase (HGD) gene, leading to the accumulation of homogentisic acid (HGA), causing severe inflammatory conditions. Recently, the presence of serum amyloid A (SAA) has been reported in AKU tissues, classifying AKU as novel secondary amyloidosis; AA amyloidosis is characterized by the extracellular tissue deposition of fibrils composed of fragments of SAA. AA amyloidosis may complicate several chronic inflammatory conditions, like rheumatoid arthritis, ankylosing spondylitis, inflammatory bowel disease, chronic infections, neoplasms, etc. Treatments of AA amyloidosis relieve inflammatory disorders by reducing SAA concentrations; however, no definitive therapy is currently available. SAA regulation is a crucial step to improve AA secondary amyloidosis treatments. Here, applying a comprehensive in vitro and in silico approach, we provided evidence that HGA is a disruptor modulator of SAA, able to enhance its polymerization, fibril formation, and aggregation upon SAA/SAP colocalization. In silico studies deeply dissected the SAA misfolding molecular pathway and SAA/HGA binding, suggesting novel molecular insights about it. Our results could represent an important starting point for identifying novel therapeutic strategies in AKU and AA secondary amyloidosis-related diseases.

Exploring the Antioxidant and Anti-Inflammatory Potential of Saffron (Crocus sativus) Tepals Extract within the Circular Bioeconomy

Repurposing saffron (Crocus sativus) waste presents a sustainable strategy for generating high-value products within the bioeconomy framework. Typically, flower components are discarded after stigma harvest, resulting in significant waste-350 kg of tepals per kilogram of stigmas. This research employed a comprehensive approach, integrating bioactivity studies (in vitro and in silico) with Life Cycle Assessment (LCA) evaluations, to extract and assess bioactive compounds from C. sativus tepals sourced in Tuscany, Italy. Phytochemical characterization using UPLC-MS/MS revealed a high abundance and variety of flavonoids in the hydro-ethanolic extract (CST). The antioxidant capacity was validated through various assays, and the ability to mitigate H2O2-induced oxidative stress and enhance fermentation was demonstrated in Saccharomyces cerevisiae. This study reports that C. sativus tepals extract reduces oxidative stress and boosts ethanol fermentation in yeast, paving the way for applications in the food and biofuels sectors. Further validation in RAW 264.7 macrophages confirmed CST's significant anti-inflammatory effects, indicating its potential for pharmaceutical, cosmeceutical, and nutraceutical applications. In silico studies identified potential targets involved in antioxidant and anti-inflammatory processes, shedding light on possible interaction mechanisms with Kaempferol 3-O-sophoroside (KOS-3), the predominant compound in the extract. The integration of LCA studies highlighted the environmental benefits of this approach. Overall, this research underscores the value of using waste-derived extracts through "green" methodologies, offering a model that may provide significant advantages for further evaluations compared to traditional methodologies and supporting the circular bioeconomy.

Traceability and authentication in agri-food production: A multivariate approach to the characterization ofthe Italian food excellence elephant garlic (Allium ampeloprasum L.), a vasoactive nutraceutical

A research platform for food authentication was set up by combining stable isotope ratio analysis, metabolomics by gas and liquid mass-spectrometry and NMR investigations, chemometric analyses for food excellences. This multi-analytical approach was tested on samples of elephant garlic (Allium ampeloprasum L.), a species belonging to the same genus of common garlic (Allium ampeloprasum L.), mainly produced in southern Tuscany-(Allium ampeloprasum). The isotopic composition allowed the product to be geographically characterized. Flavonoids, like (+)-catechin, cinnamic acids, quercetin glycosides were identified. The samples showed also a significant amount of dipeptides, sulphur-containing metabolites and glutathione, the latter of which could be considered a molecular marker of the analyzed elephant garlic. For nutraceutical profiling to reach quality labels, extracts were investigated in specific biological assays, displaying interesting vasorelaxant properties in rat aorta by mediating nitric oxide release from the endothelium and exhibited positive inotropic and negative chronotropic effects in rat perfused heart.

Current insights and future perspectives of flavonoids: A promising antihypertensive approach

Hypertension, or high blood pressure (BP), is a complex disease influenced by various risk factors. It is characterized by persistent elevation of BP levels, typically exceeding 140/90 mmHg. Endothelial dysfunction and reduced nitric oxide (NO) bioavailability play crucial roles in hypertension development. L-NG-nitro arginine methyl ester (L-NAME), an analog of L-arginine, inhibits endothelial NO synthase (eNOS) enzymes, leading to decreased NO production and increased BP. Animal models exposed to L-NAME manifest hypertension, making it a useful design for studying the hypertension condition. Natural products have gained interest as alternative approaches for managing hypertension. Flavonoids, abundant in fruits, vegetables, and other plant sources, have potential cardiovascular benefits, including antihypertensive effects. Flavonoids have been extensively studied in cell cultures, animal models, and, to lesser extent, in human trials to evaluate their effectiveness against L-NAME-induced hypertension. This comprehensive review summarizes the antihypertensive activity of specific flavonoids, including quercetin, luteolin, rutin, troxerutin, apigenin, and chrysin, in L-NAME-induced hypertension models. Flavonoids possess antioxidant properties that mitigate oxidative stress, a major contributor to endothelial dysfunction and hypertension. They enhance endothelial function by promoting NO bioavailability, vasodilation, and the preservation of vascular homeostasis. Flavonoids also modulate vasoactive factors involved in BP regulation, such as angiotensin-converting enzyme (ACE) and endothelin-1. Moreover, they exhibit anti-inflammatory effects, attenuating inflammation-mediated hypertension. This review provides compelling evidence for the antihypertensive potential of flavonoids against L-NAME-induced hypertension. Their multifaceted mechanisms of action suggest their ability to target multiple pathways involved in hypertension development. Nonetheless, the reviewed studies contribute to the evidence supporting the useful of flavonoids for hypertension prevention and treatment. In conclusion, flavonoids represent a promising class of natural compounds for combating hypertension. This comprehensive review serves as a valuable resource summarizing the current knowledge on the antihypertensive effects of specific flavonoids, facilitating further investigation and guiding the development of novel therapeutic strategies for hypertension management.

Molecular and Evolution In Silico Studies Unlock the h4-HPPD C-Terminal Tail Gating Mechanism

The enzyme 4-hydroxyphenylpyruvate dioxygenase (4-HPPD) is involved in the catabolism of the amino acid tyrosine in organisms such as bacteria, plants, and animals. It catalyzes the conversion of 4-hydroxyphenylpyruvate to a homogenisate in the presence of molecular oxygen and Fe(II) as a cofactor. This enzyme represents a key step in the biosynthesis of important compounds, and its activity deficiency leads to severe, rare autosomal recessive disorders, like tyrosinemia type III and hawkinsinuria, for which no cure is currently available. The 4-HPPD C-terminal tail plays a crucial role in the enzyme catalysis/gating mechanism, ensuring the integrity of the active site for catalysis through fine regulation of the C-terminal tail conformation. However, despite growing interest in the 4-HPPD catalytic mechanism and structure, the gating mechanism remains unclear. Furthermore, the absence of the whole 3D structure makes the bioinformatic approach the only possible study to define the enzyme structure/molecular mechanism. Here, wild-type 4-HPPD and its mutants were deeply dissected by applying a comprehensive bioinformatics/evolution study, and we showed for the first time the entire molecular mechanism and regulation of the enzyme gating process, proposing the full-length 3D structure of human 4-HPPD and two novel key residues involved in the 4-HPPD C-terminal tail conformational change.

Synthetic derivatives of natural cinnamic acids as potential anti-colorectal cancer agents

Cinnamic acid and its derivatives represent attractive building blocks for the development of pharmacological tools. A series of piperoniloyl and cinnamoyl-based amides (6-9 a-f) have been synthesized and assayed against a wide panel of colorectal cancer (CRC) cells, with the aim of finding promising anticancer agents. Among all twenty-four synthesized molecules, 7a, 7e-f, 9c, and 9f displayed the best antiproliferative activity. The induced G1 cell cycle arrest and the increase in apoptotic cell death was seen in FACS analysis and western Blotting in the colon tumor cell lines HCT116, SW480, LoVo, and HT29, but not in the nontumor cell line HCEC. In particular, 9f overcame the resistance of HT29 cells, which have a mutant p53 and BRAF. Furthermore, 9f, amide of piperonilic acid with the 3,4-dichlorobenzyl substituent upregulated p21, which is involved in cell cycle arrest as well as in apoptosis induction. Cinnamic acid derivatives might be potential anticancer compounds, useful for the development of promising anti-CRC agents.

Nutritionally enriched tomatoes (Solanum lycopersicum L.) grown with wood distillate: chemical and biological characterization for quality assessment

Bio-based products are nowadays useful tools able to affect the productivity and quality of conventionally cultivated crops. Several bio-based products are currently on the market; one of the newest and most promising is the wood distillate (WD) derived from the pyrolysis process of waste biomass after timber. Its foliar application has been widely investigated and shown to promote the antioxidant profile of cultivated crops. WD was used here as additive for the cultivation of tomato (Solanum lycopersicum L.) plants. The application improved quality (chemical) parameters, minerals, polyphenols, and lycopene contents of tomato fruits. The extracts of WD-treated and untreated tomatoes have been chemically and biologically characterized. The 1 H-NMR and ESI-mass spectrometry analyses of the extracts revealed the presence of different fatty acids, amino acids and sugars. In particular, the WD-treated tomatoes showed the presence of pyroglutamic acid and phloridzin derivatives, but also dihydrokaempferol, naringenin glucoside, cinnamic acid, and kaempferol-3-O-glucoside. When tested in cells, the extracts showed a promising anti-inflammatory profile in lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophages. Furthermore, the extracts displayed a slight vasorelaxant activity on rat aorta rings (either endothelium-denuded or endothelium-intact) pre-contracted with phenylephrine or potassium chloride. PRACTICAL APPLICATION: Wood distillate has been used for tomato plant growth. Tomatoes showed improved nutritional parameters, and their extracts displayed antioxidant and anti-inflammatory activities.

Synthesis and In Vivo Antiarrhythmic Activity Evaluation of Novel Scutellarein Analogues as Voltage-Gated Nav1.5 and Cav1.2 Channels Blockers

Malignant cardiac arrhythmias with high morbidity and mortality have posed a significant threat to our human health. Scutellarein, a metabolite of Scutellarin which is isolated from Scutellaria altissima L., presents excellent therapeutic effects on cardiovascular diseases and could further be metabolized into methylated forms. A series of 22 new scutellarein derivatives with hydroxyl-substitution based on the scutellarin metabolite in vivo was designed, synthesized via the conjugation of the scutellarein scaffold with pharmacophores of FDA-approved antiarrhythmic medications and evaluated for their antiarrhythmic activity through the analyzation of the rat number of arrhythmia recovery, corresponding to the recovery time and maintenance time in the rat model of barium chloride-induced arrhythmia, as well as the cumulative dosage of aconitine required to induce VP, VT, VF and CA in the rat model of aconitine-induced arrhythmia. All designed compounds could shorten the time of the arrhythmia continuum induced by barium chloride, indicating that 4'-hydroxy substituents of scutellarein had rapid-onset antiarrhythmic effects. In addition, nearly all of the compounds could normalize the HR, RR, QRS, QT and QTc interval, as well as the P/T waves' amplitude. The most promising compound 10e showed the best antiarrhythmic activity with long-term efficacy and extremely low cytotoxicity, better than the positive control scutellarein. This result was also approved by the computational docking simulation. Most importantly, patch clamp measurements on Nav1.5 and Cav1.2 channels indicated that compound 10e was able to reduce the INa and ICa in a concentration-dependent manner and left-shifted the inactivation curve of Nav1.5. Taken together, all compounds were considered to be antiarrhythmic. Compound 10e even showed no proarrhythmic effect and could be classified as Ib Vaughan Williams antiarrhythmic agents. What is more, compound 10e did not block the hERG potassium channel which highly associated with cardiotoxicity.

Artificial intelligence-driven identification of morin analogues acting as CaV1.2 channel blockers: Synthesis and biological evaluation

Morin is a vasorelaxant flavonoid, whose activity is ascribable to Ca_V1.2 channel blockade that, however, is weak as compared to that of clinically used therapeutic agents. A conventional strategy to circumvent this drawback is to synthesize new derivatives differently decorated and, in this context, morin-derivatives able to interact with Ca_V1.2 channels were found by employing the potential of PLATO in target fishing and reverse screening. Three different derivatives (5a-c) were selected as promising tools, synthesized, and investigated in in vitro functional studies using rat aorta rings and rat tail artery myocytes. 5a-c were found more effective vasorelaxant agents than the naturally occurring parent compound and antagonized both electro- and pharmaco-mechanical coupling in an endothelium-independent manner. 5a, the series' most potent, reduced also Ca²⁺ mobilization from intracellular store sites. Furthermore, 5a≈5c > 5b inhibited Ba²⁺ current through Ca_V1.2 channels. However, compound 5a caused also a concentration-dependent inhibition of K_Ca1.1 channel currents.

Novel Labdane Diterpenes-Based Synthetic Derivatives: Identification of a Bifunctional Vasodilator That Inhibits CaV1.2 and Stimulates KCa1.1 Channels

Sesquiterpenes such as leucodin and the labdane-type diterpene manool are natural compounds endowed with remarkably in vitro vasorelaxant and in vivo hypotensive activities. Given their structural similarity with the sesquiterpene lactone (+)-sclareolide, this molecule was selected as a scaffold to develop novel vasoactive agents. Functional, electrophysiology, and molecular dynamics studies were performed. The opening of the five-member lactone ring in the (+)-sclareolide provided a series of labdane-based small molecules, promoting a significant in vitro vasorelaxant effect. Electrophysiology data identified 7 as a Ca_V1.2 channel blocker and a K_Ca1.1 channel stimulator. These activities were also confirmed in the intact vascular tissue. The significant antagonism caused by the Ca_V1.2 channel agonist Bay K 8644 suggested that 7 might interact with the dihydropyridine binding site. Docking and molecular dynamic simulations provided the molecular basis of the Ca_V1.2 channel blockade and K_Ca1.1 channel stimulation produced by 7. Finally, 7 reduced coronary perfusion pressure and heart rate, while prolonging conduction and refractoriness of the atrioventricular node, likely because of its Ca²⁺ antagonism. Taken together, these data indicate that the labdane scaffold represents a valuable starting point for the development of new vasorelaxant agents endowed with negative chronotropic properties and targeting key pathways involved in the pathophysiology of hypertension and ischemic cardiomyopathy.

Extra Virgin Olive Oil Extracts of Indigenous Southern Tuscany Cultivar Act as Anti-Inflammatory and Vasorelaxant Nutraceuticals

Extra virgin olive oil (EVOO) is the typical source of fats in the Mediterranean diet. While fatty acids are essential for the EVOO nutraceutical properties, multiple biological activities are also due to the presence of polyphenols. In this work, autochthonous Tuscany EVOOs were chemically characterized and selected EVOO samples were extracted to obtain hydroalcoholic phytocomplexes, which were assayed to establish their anti-inflammatory and vasorelaxant properties. The polar extracts were characterized via 1H-NMR and UHPLC-HRMS to investigate the chemical composition and assayed in CaCo-2 cells exposed to glucose oxidase or rat aorta rings contracted by phenylephrine. Apigenin and luteolin were found as representative flavones; other components were pinoresinol, ligstroside, and oleuropein. The extracts showed anti-inflammatory and antioxidant properties via modulation of NF-κB and Nrf2 pathways, respectively, and good vasorelaxant activity, both in the presence and absence of an intact endothelium. In conclusion, this study evaluated the nutraceutical properties of autochthonous Tuscany EVOO cv., which showed promising anti-inflammatory and vasorelaxant effects.

2-Hydroxy-5-(3,5,7-trihydroxy-4-oxo-4H-chromen-2-yl)phenyl (E)-3-(4-hydroxy-3-methoxyphenyl)acrylate: Synthesis, In Silico Analysis and In Vitro Pharmacological Evaluation

Quercetin and ferulic acid are two phytochemicals extensively represented in the plant kingdom and daily consumed in considerable amounts through diets. Due to a common phenolic structure, these two molecules share several pharmacological properties, e.g., antioxidant and free radical scavenging, anti-cancer, anti-inflammatory, anti-arrhythmic, and vasorelaxant. The aim of the present work was the combination of the two molecules in a single chemical entity, conceivably endowed with more efficacious vasorelaxant activity. Preliminary in silico studies herein described suggested that the new hybrid compound bound spontaneously and with high affinity on the KCa1.1 channel. Thus, the synthesis of the 3′-ferulic ester derivative of quercetin was achieved and its structure confirmed by 1H- and 13C-NMR spectra, HSQC and HMBC experiments, mass spectrometry, and elementary analysis. The effect of the new hybrid compound on vascular KCa1.1 and CaV1.2 channels revealed a partial loss of the stimulatory activity that characterizes the parent compound quercetin. Therefore, further studies are necessary to identify a better strategy to improve the vascular properties of this flavonoid.

7-Docosahexaenoyl-Quercetin

Fatty acids and polyphenols represent different classes of pharmacologically active molecules. Hybrid derivatives of these compounds are interesting therapeutic tools. They could be obtained using enzymatic approaches, which allow regioselective derivatizations. In this short note, the pancreatic porcine lipase was employed to mediate the regioselective synthesis of 7-docosahexaenoyl-quercetin was described. The C-7 regioisomer formation was confirmed by 1H-NMR experiment. Generally, in this approach the alcoholic OH- was preferred when present. Nevertheless, in this case, it was demonstrated that the hindrance of the acyl group is a variable to obtain a good regioselectivity in C-7 position, employing only one-step reaction.

Flavonoids and hERG channels: Friends or foes?

The cardiac action potential is regulated by several ion channels. Drugs capable to block these channels, in particular the human ether-à-go-go-related gene (hERG) channel, also known as K_V11.1 channel, may lead to a potentially lethal ventricular tachyarrhythmia called "Torsades de Pointes". Thus, evaluation of the hERG channel off-target activity of novel chemical entities is nowadays required to safeguard patients as well as to avoid attrition in drug development. Flavonoids, a large class of natural compounds abundantly present in food, beverages, herbal medicines, and dietary food supplements, generally escape this assessment, though consumed in consistent amounts. Continuously growing evidence indicates that these compounds may interact with the hERG channel and block it. The present review, by examining numerous studies, summarizes the state-of-the-art in this field, describing the most significant examples of direct and indirect inhibition of the hERG channel current operated by flavonoids. A description of the molecular interactions between a few of these natural molecules and the Rattus norvegicus channel protein, achieved by an in silico approach, is also presented.