Synthesis of (-)-[4-3H]epigallocatechin gallate and its metabolic fate in rats after intravenous administration

Comprehensive Review of EGCG Modification: Esterification Methods and Their Impacts on Biological Activities

Epigallocatechin gallate (EGCG), the key constituent of tea polyphenols, presents challenges in terms of its lipid solubility, stability, and bioavailability because of its polyhydroxy structure. Consequently, structural modifications are imperative to enhance its efficacy. This paper comprehensively reviews the esterification techniques applied to EGCG over the past two decades and their impacts on bioactivities. Both chemical and enzymatic esterification methods involve catalysts, solvents, and hydrophobic groups as critical factors. Although the chemical method is cost-efficient, it poses challenges in purification; on the other hand, the enzymatic approach offers improved selectivity and simplified purification processes. The biological functions of EGCG are inevitably influenced by the structural changes incurred through esterification. The antioxidant capacity of EGCG derivatives can be compromised under certain conditions by reducing hydroxyl groups, while enhancing lipid solubility and stability can strengthen their antiviral, antibacterial, and anticancer properties. Additionally, esterification broadens the utility of EGCG in food applications. This review provides critical insights into developing cost-effective and environmentally sustainable selective esterification methods, as well as emphasizes the elucidation of the bioactive mechanisms of EGCG derivatives to facilitate their widespread adoption in food processing, healthcare products, and pharmaceuticals.

Tea's anti-obesity properties, cardiometabolic health-promoting potentials, bioactive compounds, and adverse effects: A review focusing on white and green teas

Tea is one of the most commonly consumed beverages in the world. Morocco, Japan, and China have consumed green tea for centuries. White tea, which is a variety of green teas, is very popular in China and is highly revered for its taste. Presently, both teas are consumed in other countries around the world, even as functional ingredients, and novel research is constantly being conducted in these areas. We provide an update on the health benefits of white and green teas in this review, based on recent research done to present. After a general introduction, we focused on tea's anti-obesity and human health-promoting potential, adverse effects, and new approaches to tea and its bioactive compounds. It has been found that the health benefits of tea are due to its bioactive components, mainly phenolic compounds. Of these, catechins are the most abundant. This beverage (or its extracts) has potential anti-inflammatory and antioxidant properties, which could contribute to body weight control and the improvement of several chronic diseases. However, some studies have mentioned the possibility of toxic effects; therefore, reducing tea consumption is a good idea, especially during the last trimester of pregnancy. Additionally, new evidence will provide insight into the possible effects of tea on the human gut microbiota, and even on the viruses responsible for SARS-CoV-2. A beverage such as this may favor beneficial gut microbes, which may have important implications due to the influence of gut microbiota on human health.

Metabolism of phenolics in coffee and plant-based foods by canonical pathways: an assessment of the role of fatty acid β-oxidation to generate biologically-active and -inactive intermediates

ω-Phenyl-alkenoic acids are abundant in coffee, fruits, and vegetables. Along with ω-phenyl-alkanoic acids, they are produced from numerous dietary (poly)phenols and aromatic amino acids in vivo. This review addresses how phenyl-ring substitution and flux modulates their gut microbiota and endogenous β-oxidation. 3',5'-Dihydroxy-derivatives (from alkyl-resorcinols, flavanols, proanthocyanidins), and 4'-hydroxy-phenolic acids (from tyrosine, p-coumaric acid, naringenin) are β-oxidation substrates yielding benzoic acids. In contrast, 3',4',5'-tri-substituted-derivatives, 3',4'-dihydroxy-derivatives and 3'-methoxy-4'-hydroxy-derivatives (from coffee, tea, cereals, many fruits and vegetables) are poor β-oxidation substrates with metabolism diverted via gut microbiota dehydroxylation, phenylvalerolactone formation and phase-2 conjugation, possibly a strategy to conserve limited pools of coenzyme A. 4'-Methoxy-derivatives (citrus fruits) or 3',4'-dimethoxy-derivatives (coffee) are susceptible to hepatic "reverse" hydrogenation suggesting incompatibility with enoyl-CoA-hydratase. Gut microbiota-produced 3'-hydroxy-4'-methoxy-derivatives (citrus fruits) and 3'-hydroxy-derivatives (numerous (poly)phenols) are excreted as the phenyl-hydracrylic acid β-oxidation intermediate suggesting incompatibility with hydroxy-acyl-CoA dehydrogenase, albeit with considerable inter-individual variation. Further investigation is required to explain inter-individual variation, factors determining the amino acid to which C6-C3 and C6-C1 metabolites are conjugated, the precise role(s) of l-carnitine, whether glycine might be limiting, and whether phenolic acid-modulation of β-oxidation explains how phenolic acids affect key metabolic conditions, such as fatty liver, carbohydrate metabolism and insulin resistance.

Epigallocatechin gallate as a nutraceutical to potentially target the metabolic syndrome: novel insights into therapeutic effects beyond its antioxidant and anti-inflammatory properties

Epigallocatechin gallate (EGCG) is one of the most abundant and powerful flavonoids contained in green tea. Because of the global increase in green tea consumption, there has been a general interest in understanding its health benefits, including its bioactive compounds like EGCG. Indeed, preclinical evidence already indicates that EGCG demonstrated a strong antioxidant and anti-inflammatory properties that could be essential in protecting against metabolic syndrome. The current review explores clinical evidence reporting on the beneficial effects of EGCG supplementation in obese subjects or patients with diverse metabolic complications that include type 2 diabetes and cardiovascular disease. The discussion incorporates the impact of different formulations of EGCG, as well as the effective doses and treatment duration. Importantly, besides highlighting the potential use of EGCG as a nutraceutical, the current review also discusses crucial evidence related to its pharmaceutical development as an agent to hinder metabolic diseases, including its bioavailability and metabolism profile, as well as its well-known biological properties.

Enzymatic Synthesis and Antioxidant Activity of Mono- and Diacylated Epigallocatechin Gallate and Related By-Products

Ester derivatives of epigallocatechin gallate (EGCG) were enzymatically prepared by one-step transesterification with vinyl fatty acids consisting of varying acyl groups ranging from 2 to 18 carbon atoms (acetate, butyrate, caproate, caprylate, caprate, laurate, myristate, and stearate). The main acylation products were EGCG monoesters and diesters. However, due to the presence of trace amounts of water in the reaction medium, minor but noticeable hydrolysis of EGCG also occurred as a side reaction which required a prolonged purification process due to the formation of by-products such as gallic acid, epigallocatechin, and their esters. In this contribution, 8 EGCG monoesters, 7 EGCG diesters, and 7 gallic acid monoesters were isolated and purified, and the acylation positions were characterized. Meanwhile, several classical chemicals (DPPH, ABTS, FRAP, and Fe²⁺ chelation assays), food (β-carotene bleaching assay), and biological (LDL and DNA oxidation assays) models were conducted to evaluate and systematically compare their antioxidant efficacy. The lipophilicity of the EGCG derivatives increased with the increasing chain length of the acyl group and led to the fluctuation of their antioxidant efficacies. Three main factors, namely, the reduction potential, the partition coefficient of solute in the solvent system, and the steric hindrance of antioxidant agent and related substrates were considered to help explain the biased antioxidant performance of EGCG derivatives upon acylation modification. The results strongly suggest that the acylated EGCGs have great potential as lipophilic alternatives to the water-soluble EGCG in lipid-based matrices.

Chemico-biological aspects of (-)-epigallocatechin-3-gallate (EGCG) to improve its stability, bioavailability and membrane permeability: Current status and future prospects

Natural products have been a bedrock for drug discovery for decades. (-)-Epigallocatechin-3-gallate (EGCG) is one of the widely studied natural polyphenolic compounds derived from green tea. It is the key component believed to be responsible for the medicinal value of green tea. Significant studies implemented in in vitro, in cellulo, and in vivo models have suggested its anti-oxidant, anti-cancer, anti-diabetic, anti-inflammatory, anti-microbial, neuroprotective activities etc. Despite having such a wide array of therapeutic potential and promising results in preclinical studies, its applicability to humans has encountered with rather limited success largely due to the poor bioavailability, poor membrane permeability, rapid metabolic clearance and lack of stability of EGCG. Therefore, novel techniques are warranted to address those limitations so that EGCG or its modified analogs can be used in the clinical setup. This review comprehensively covers different strategies such as structural modifications, nano-carriers as efficient drug delivery systems, synergistic studies with other bioactivities to improve the chemico-biological aspects (e.g., stability, bioavailability, permeability, etc.) of EGCG for its enhanced pharmacokinetics and pharmacological properties, eventually enhancing its therapeutic potentials. We think this review article will serve as a strong platform with comprehensive literature on the development of novel techniques to improve the bioavailability of EGCG so that it can be translated to the clinical applications.

(-)-Epigallocatechin-3-Gallate (EGCG) Modulates the Composition of the Gut Microbiota to Protect Against Radiation-Induced Intestinal Injury in Mice

The high radiosensitivity of the intestinal epithelium limits the outcomes of radiotherapy against abdominal malignancies, which results in poor prognosis. Currently, no effective prophylactic or therapeutic strategy is available to mitigate radiation toxicity in the intestine. Our previous study revealed that the green tea polyphenol (-)-epigallocatechin-3-gallate (EGCG) attenuates radiation-induced intestinal injury (RIII). The aim of the present study was to determine the effect of EGCG on the intestinal flora of irradiated mice. EGCG administration reduced radiation-induced intestinal mucosal injury, and significantly increased the number of Lgr5⁺ intestinal stem cells (ISCs) and Ki67⁺ crypt cells. In addition, EGCG reversed radiation-induced gut dysbiosis, restored the Firmicutes/Bacteroidetes ratio, and increased the abundance of beneficial bacteria. Our findings provide novel insight into EGCG-mediated remission of RIII, revealing that EGCG could be a potential modulator of gut microbiota to prevent and treat RIII.

Liposomal Nanoformulation as a Carrier for Curcumin and pEGCG—Study on Stability and Anticancer Potential

Nanoformulations are regarded as a promising tool to enable the efficient delivery of active pharmaceutical ingredients to the target site. One of the best-known and most studied nanoformulations are liposomes—spherical phospholipid bilayered nanocarriers resembling cell membranes. In order to assess the possible effect of a mixture of polyphenols on both the stability of the formulation and its biological activity, two compounds were embedded in the liposomes—(i) curcumin (CUR), (ii) a peracetylated derivative of (−)-epigallocatechin 3-O-gallate (pEGCG), and (iii) a combination of the aforementioned. The stability of the formulations was assessed in two different temperature ranges (4–8 and 20 °C) by monitoring both the particle size and their concentration. It was found that after 28 days of the experiment, the liposomes remained largely unchanged in terms of the particle size distribution, with the greatest change from 130 to 146 nm. The potential decomposition of the carried substances was evaluated using HPLC. The combined CUR and pEGCG was sensitive to temperature conditions; however its stability was greatly increased when compared to the solutions of the individual compounds alone—up to 9.67% of the initial concentration of pEGCG in liposomes after 28 days storage compared to complete decomposition within hours for the non-encapsulated sample. The potential of the prepared formulations was assessed in vitro on prostate (LNCaP) and bladder cancer (5637) cell lines, as well as on a non-cancerous human lung fibroblast cell line (MRC-5), with the highest activity of IC₅₀ equal 15.33 ± 2.03 µM for the mixture of compounds towards the 5637 cell line.

Effects of Green Tea (-)-Epigallocatechin-3-Gallate (EGCG) on Cardiac Function - A Review of the Therapeutic Mechanism and Potentials

Heart disease, the leading cause of death globally, refers to various illnesses that affect heart structure and function. Specific abnormalities affecting cardiac muscle contractility and remodeling and common factors including oxidative stress, inflammation, and apoptosis underlie the pathogenesis of heart diseases. Epidemiology studies have associated green tea consumption with lower morbidity and mortality of cardiovascular diseases, including heart and blood vessel dysfunction. Among the various compounds found in green tea, catechins are believed to play a significant role in producing benefits to cardiovascular health. Comprehensive literature reviews have been published to summarize the tea catechins' antioxidative, anti-inflammatory, and anti-apoptosis effects in the context of various diseases, such as cardiovascular diseases, cancers, and metabolic diseases. However, recent studies on tea catechins, especially the most abundant (-)-Epigallocatechin-3-Gallate (EGCG), revealed their capabilities in regulating cardiac muscle contraction by directly altering myofilament Ca2+ sensitivity on force development and Ca2+ ion handling in cardiomyocytes under both physiological and pathological conditions. In vitro and in vivo data also demonstrated that green tea extract or EGCG protected or rescued cardiac function, independent of their well-known effects against oxidative stress and inflammation. This minireview will focus on the specific effects of tea catechins on heart muscle contractility at the molecular and cellular level, revisit their effects on oxidative stress and inflammation in a variety of heart diseases, and discuss EGCG's potential as one of the lead compounds for new drug discovery for heart diseases.

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

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

Pharmacology of Catechins in Ischemia-Reperfusion Injury of the Heart

Catechins represent a group of polyphenols that possesses various beneficial effects in the cardiovascular system, including protective effects in cardiac ischemia-reperfusion (I/R) injury, a major pathophysiology associated with ischemic heart disease, myocardial infarction, as well as with cardioplegic arrest during heart surgery. In particular, catechin, (−)-epicatechin, and epigallocatechin gallate (EGCG) have been reported to prevent cardiac myocytes from I/R-induced cell damage and I/R-associated molecular changes, finally, resulting in improved cell viability, reduced infarct size, and improved recovery of cardiac function after ischemic insult, which has been widely documented in experimental animal studies and cardiac-derived cell lines. Cardioprotective effects of catechins in I/R injury were mediated via multiple molecular mechanisms, including inhibition of apoptosis; activation of cardioprotective pathways, such as PI3K/Akt (RISK) pathway; and inhibition of stress-associated pathways, including JNK/p38-MAPK; preserving mitochondrial function; and/or modulating autophagy. Moreover, regulatory roles of several microRNAs, including miR-145, miR-384-5p, miR-30a, miR-92a, as well as lncRNA MIAT, were documented in effects of catechins in cardiac I/R. On the other hand, the majority of results come from cell-based experiments and healthy small animals, while studies in large animals and studies including comorbidities or co-medications are rare. Human studies are lacking completely. The dosages of compounds also vary in a broad scale, thus, pharmacological aspects of catechins usage in cardiac I/R are inconclusive so far. Therefore, the aim of this focused review is to summarize the most recent knowledge on the effects of catechins in cardiac I/R injury and bring deep insight into the molecular mechanisms involved and dosage-dependency of these effects, as well as to outline potential gaps for translation of catechin-based treatments into clinical practice.

Nutraceuticals in the Mediterranean Diet: Potential Avenues for Breast Cancer Treatment

The traditional Mediterranean Diet constitutes a food model that refers to the dietary patterns of the population living in countries bordering the Mediterranean Sea in the early 1960s. A huge volume of literature data suggests that the Mediterranean-style diet provides several dietary compounds that have been reported to exert beneficial biological effects against a wide spectrum of chronic illnesses, such as cardiovascular and neurodegenerative diseases and cancer including breast carcinoma. Among bioactive nutrients identified as protective factors for breast cancer, natural polyphenols, retinoids, and polyunsaturated fatty acids (PUFAs) have been reported to possess antioxidant, anti-inflammatory, immunomodulatory and antitumoral properties. The multiple anticancer mechanisms involved include the modulation of molecular events and signaling pathways associated with cell survival, proliferation, differentiation, migration, angiogenesis, antioxidant enzymes and immune responses. This review summarizes the anticancer action of some polyphenols, like resveratrol and epigallocatechin 3-gallate, retinoids and omega-3 PUFAs by highlighting the important hallmarks of cancer in terms of (i) cell cycle growth arrest, (ii) apoptosis, (iii) inflammation and (iv) angiogenesis. The data collected from in vitro and in vivo studies strongly indicate that these natural compounds could be the prospective candidates for the future anticancer therapeutics in breast cancer disease.

The Neuroprotective Effect of Tea Polyphenols on the Regulation of Intestinal Flora

Tea polyphenols (TPs) are the general compounds of natural polyhydroxyphenols extracted in tea. Although a large number of studies have shown that TPs have obvious neuroprotective and neuro repair effects, they are limited due to the low bioavailability in vivo. However, TPs can act indirectly on the central nervous system by affecting the “microflora–gut–brain axis”, in which the microbiota and its composition represent a factor that determines brain health. Bidirectional communication between the intestinal microflora and the brain (microbe–gut–brain axis) occurs through a variety of pathways, including the vagus nerve, immune system, neuroendocrine pathways, and bacteria-derived metabolites. This axis has been shown to influence neurotransmission and behavior, which is usually associated with neuropsychiatric disorders. In this review, we discuss that TPs and their metabolites may provide benefits by restoring the imbalance of intestinal microbiota and that TPs are metabolized by intestinal flora, to provide a new idea for TPs to play a neuroprotective role by regulating intestinal flora.

Epigallocatechin Gallate for Management of Heavy Metal-Induced Oxidative Stress: Mechanisms of Action, Efficacy, and Concerns

In this review, we highlight the effects of epigallocatechin gallate (EGCG) against toxicities induced by heavy metals (HMs). This most active green tea polyphenol was demonstrated to reduce HM toxicity in such cells and tissues as testis, liver, kidney, and neural cells. Several protective mechanisms that seem to play a pivotal role in EGCG-induced effects, including reactive oxygen species scavenging, HM chelation, activation of nuclear factor erythroid 2-related factor 2 (Nrf2), anti-inflammatory effects, and protection of mitochondria, are described. However, some studies, especially in vitro experiments, reported potentiation of harmful HM actions in the presence of EGCG. The adverse impact of EGCG on HM toxicity may be explained by such events as autooxidation of EGCG, EGCG-mediated iron (Fe3+) reduction, depletion of intracellular glutathione (GSH) levels, and disruption of mitochondrial functions. Furthermore, challenges hampering the potential EGCG application related to its low bioavailability and proper dosing are also discussed. Overall, in this review, we point out insights into mechanisms that might account for both the beneficial and adverse effects of EGCG in HM poisoning, which may have a bearing on the design of new therapeutics for HM intoxication therapy.

EGCG ameliorates neuronal and behavioral defects by remodeling gut microbiota and TotM expression in Drosophila models of Parkinson's disease

Parkinson's disease (PD) is the second most common neurodegenerative disease. Eigallocatechin-3-gallate (EGCG), the major polyphenol in green tea, is known to exert a beneficial effect on PD patients. Although some mechanisms were suggested to underlie this intervention, it remains unknown if the EGCG-mediated protection was achieved by remodeling gut microbiota. In the present study, 0.1 mM or 0.5 mM EGCG was administered to the Drosophila melanogaster with PINK1 (PTEN induced putative kinase 1) mutations, a prototype PD model, and their behavioral performances, as well as neuronal/mitochondrial morphology (only for 0.5 mM EGCG treatment) were determined. According to the results, the mutant PINK1^B9 flies exhibited dopaminergic, survival, and behavioral deficits, which were rescued by EGCG supplementation. Meanwhile, EGCG resulted in profound changes in gut microbial compositions in PINK1^B9 flies, restoring the abundance of a set of bacteria. Notably, EGCG protection was blunted when gut microbiota was disrupted by antibiotics. We further isolated four bacterial strains from fly guts and the supplementation of individual Lactobacillus plantarum or Acetobacter pomorum strain exacerbated the neuronal and behavioral dysfunction of PD flies, which could not be rescued by EGCG. Transcriptomic analysis identified TotM as the central gene responding to EGCG or microbial manipulations. Genetic ablation of TotM blocked the recovery activity of EGCG, suggesting that EGCG-mediated protection warrants TotM. Apart from familial form, EGCG was also potent in improving sporadic PD symptoms induced by rotenone treatment, wherein gut microbiota shared regulatory roles. Together, our results suggest the relevance of the gut microbiota-TotM pathway in EGCG-mediated neuroprotection, providing insight into indirect mechanisms underlying nutritional intervention of Parkinson's disease.

Epigallocatechin Gallate Modulates Muscle Homeostasis in Type 2 Diabetes and Obesity by Targeting Energetic and Redox Pathways: A Narrative Review

Obesity is associated with the hypertrophy and hyperplasia of adipose tissue, affecting the healthy secretion profile of pro- and anti-inflammatory adipokines. Increased influx of fatty acids and inflammatory adipokines from adipose tissue can induce muscle oxidative stress and inflammation and negatively regulate myocyte metabolism. Muscle has emerged as an important mediator of homeostatic control through the consumption of energy substrates, as well as governing systemic signaling networks. In muscle, obesity is related to decreased glucose uptake, deregulation of lipid metabolism, and mitochondrial dysfunction. This review focuses on the effect of epigallocatechin-gallate (EGCG) on oxidative stress and inflammation, linked to the metabolic dysfunction of skeletal muscle in obesity and their underlying mechanisms. EGCG works by increasing the expression of antioxidant enzymes, by reversing the increase of reactive oxygen species (ROS) production in skeletal muscle and regulating mitochondria-involved autophagy. Moreover, EGCG increases muscle lipid oxidation and stimulates glucose uptake in insulin-resistant skeletal muscle. EGCG acts by modulating cell signaling including the NF-κB, AMP-activated protein kinase (AMPK), and mitogen-activated protein kinase (MAPK) signaling pathways, and through epigenetic mechanisms such as DNA methylation and histone acetylation.

Oolong tea: A critical review of processing methods, chemical composition, health effects, and risk

Oolong tea (OT) is a traditional Chinese tea (Camellia sinensis) and is especially popular in south China. This review is to comprehensively summarize the miscellaneous research that has been done towards to the processing, phytochemistry, health benefit, and risk of OT. These literatures were carried out not only from different electronic databases but also from text books written in English, Japanese, and Chinese, including those traditional records tracing back to the Tang Dynasty (A.D. 618-907). The full process OT producing is depicted below in this review. The phytochemistry of OT has been comprehensively investigated. More than 100 chemical compositions have been isolated and identified. In health benefit, OT performs outstandingly in reducing obesity and controlling diabetes explained by modern pharmacological studies. (-)-Epigallocatechin-3-gallate (6) in OT prevention of cancerous cells developing. OT can also improve and reduce on heart and vascular disease, protect teeth and bone, function as anti-oxidative and antibacterial agents. This review also mentioned the risk, summarized briefly on various forms of toxicity and harmful associated with OT. In short, this review can provided a natural product library of OT, gave inspirations for further new garden systems, designed idea on quality, bioactivity-oriented screening. In addition, it is suggested more scientists and education is necessary to guarantee the stability and safety of drinking OT.

Absorption, metabolism, anti-cancer effect and molecular targets of epigallocatechin gallate (EGCG): An updated review

Green tea is one of the most popular beverages in the world, especially in Asian countries. Consumption of green tea has been demonstrated to possess many health benefits, which mainly attributed to the main bioactive compound epigallocatechin gallate (EGCG), a flavone-3-ol polyphenol, in green tea. EGCG is mainly absorbed in the intestine, and gut microbiota play a critical role in its metabolism prior to absorption. EGCG exhibits versatile bioactivities, with its anti-cancer effect most attracting due to the cancer preventive effect of green tea consumption, and a great number of studies intensively investigated its anti-cancer effect. In this review, we therefore, first stated the absorption and metabolism process of EGCG, and then summarized its anti-cancer effect in vitro and in vivo, including its manifold anti-cancer actions and mechanisms, especially its anti-cancer stem cell effect, and next highlighted its various molecular targets involved in cancer inhibition. Finally, the anti-cancer effect of EGCG analogs and nanoparticles, as well as the potential cancer promoting effect of EGCG were also discussed. Understanding of the absorption, metabolism, anti-cancer effect and molecular targets of EGCG can be of importance to better utilize it as a chemopreventive and chemotherapeutic agent.

Physiologically based pharmacokinetic modeling of tea catechin mixture in rats and humans

Although green tea (Camellia sinensis) (GT) contains a large number of polyphenolic compounds with anti-oxidative and anti-proliferative activities, little is known of the pharmacokinetics and tissue dose of tea catechins (TCs) as a chemical mixture in humans. The objectives of this study were to develop and validate a physiologically based pharmacokinetic (PBPK) model of tea catechin mixture (TCM) in rats and humans, and to predict an integrated or total concentration of TCM in the plasma of humans after consuming GT or Polyphenon E (PE). To this end, a PBPK model of epigallocatechin gallate (EGCg) consisting of 13 first-order, blood flow-limited tissue compartments was first developed in rats. The rat model was scaled up to humans by replacing its physiological parameters, pharmacokinetic parameters and tissue/blood partition coefficients (PCs) with human-specific values. Both rat and human EGCg models were then extrapolated to other TCs by substituting its physicochemical parameters, pharmacokinetic parameters, and PCs with catechin-specific values. Finally, a PBPK model of TCM was constructed by linking three rat (or human) tea catechin models together without including a description for pharmacokinetic interaction between the TCs. The mixture PBPK model accurately predicted the pharmacokinetic behaviors of three individual TCs in the plasma of rats and humans after GT or PE consumption. Model-predicted total TCM concentration in the plasma was linearly related to the dose consumed by humans. The mixture PBPK model is able to translate an external dose of TCM into internal target tissue doses for future safety assessment and dose-response analysis studies in humans. The modeling framework as described in this paper is also applicable to the bioactive chemical in other plant-based health products.

Cancer therapeutics with epigallocatechin-3-gallate encapsulated in biopolymeric nanoparticles

With the recent quantum leap in chemoprevention by dietary products, their use as cancer therapeutics is garnering worldwide attention. The concept of effortlessly fighting this deadly disease by gulping cups of green tea or swallowing green tea extract capsules is appreciated universally. Epigallocatechin-3-gallate (EGCG), a major polyphenol in green tea, has generated significant interest in controlling carcinogenesis due to its growth-inhibitory efficacy against a variety of cancers by targeting multiple signaling pathways. However, the success of EGCG in preclinical studies is difficult to translate into clinical trials due to issues of low solubility, bioavailability and an uncertain therapeutic window. The laborious and expensive journey of drugs from the laboratory to commercialization can be improved by utilizing nanoparticles as anti-cancer drug carriers. Exploitation of biopolymeric nanoparticles in recent years has improved EGCG's biodistribution, stability and tumor selectivity, revealing its superior chemopreventive effects. This review briefly summarizes recent developments regarding the targets and side effects of EGCG, complications associated with its low bioavailability and critically analyses the application of biopolymeric nanoparticles encapsulating EGCG as a next generation delivery systems.

Simultaneous Determination of Black Tea-Derived Catechins and Theaflavins in Tissues of Tea Consuming Animals Using Ultra-Performance Liquid-Chromatography Tandem Mass Spectrometry

The bioavailability, tissue distribution and metabolic fate of the major tea polyphenols, catechins and theaflavins as well as their gallated derivatives are yet to be precisely elucidated on a single identification platform for assessment of their relative bioefficacy in vivo. This is primarily due to the lack of suitable analytical tools for their simultaneous determination especially in an in vivo setting, which continues to constrain the evaluation of their relative health beneficiary potential and therefore prospective therapeutic application. Herein, we report a rapid and sensitive Ultra-Performance Liquid Chromatography Tandem Mass Spectrometry (UPLC-MS/MS) based method for the simultaneous determination of the major catechins and theaflavins in black tea infusions as well as in different vital tissues and body fluids of tea-consuming guinea pigs. This method allowed efficient separation of all polyphenols within seven minutes of chromatographic run and had a lower limit of quantification (LLOQ) of ~5 ng/ml. Using this method, almost all bioactive catechins and theaflavins could be simultaneously detected in the plasma of guinea pigs orally administered 5% black tea for 14 days. Our method could further detect the majority of these polyphenols in the lung and kidney as well as identify the major catechin metabolites in the urine of the tea-consuming animals. Overall, our study presents a novel tool for simultaneous detection and quantitation of both catechins and theaflavins in a single detection platform that could potentially enable precise elucidation of their relative bioavailability and bioefficacy as well as true health beneficiary potential in vivo. Such information would ultimately facilitate the accurate designing of therapeutic strategies utilizing high efficacy formulations of tea polyphenols for effective mitigation of oxidative damage and inflammation in humans as well as prevention of associated diseases.

The Reciprocal Interactions between Polyphenols and Gut Microbiota and Effects on Bioaccessibility

As of late, polyphenols have increasingly interested the scientific community due to their proposed health benefits. Much of this attention has focused on their bioavailability. Polyphenol-gut microbiota interactions should be considered to understand their biological functions. The dichotomy between the biotransformation of polyphenols into their metabolites by gut microbiota and the modulation of gut microbiota composition by polyphenols contributes to positive health outcomes. Although there are many studies on the in vivo bioavailability of polyphenols, the mutual relationship between polyphenols and gut microbiota is not fully understood. This review focuses on the biotransformation of polyphenols by gut microbiota, modulation of gut microbiota by polyphenols, and the effects of these two-way mutual interactions on polyphenol bioavailability, and ultimately, human health.

Epicatechin gallate, a naturally occurring polyphenol, alters the course of infection with β-lactam-resistant Staphylococcus aureus in the zebrafish embryo

(-)-epicatechin gallate (ECg) substantially modifies the properties of Staphylococcus aureus and reversibly abrogates β-lactam resistance in methicillin/oxacillin resistant (MRSA) isolates. We have determined the capacity of ECg to alter the course of infection in zebrafish embryos challenged with epidemic clinical isolate EMRSA-16. At 30 h post fertilization (hpf), embryos were infected by injection of 1–5 × 10³ colony forming units (CFU) of EMRSA-16 into the circulation valley or yolk sac. Infection by yolk sac injection was lethal with a challenge dose above 3 × 10³ CFU, with no survivors at 70 hpf. In contrast, survival at 70 hpf after injection into the circulation was 83 and 44% following challenge with 3 × 10³ and 1–5 × 10³ CFU, respectively. No significant increases in survival were noted when infected embryos were maintained in medium containing 12.5–100 μg/mL ECg with or without 4 or 16 μg/mL oxacillin. However, when EMRSA-16 was grown in medium containing 12.5 μg/mL ECg and the bacteria used to infect embryos by either the circulation valley or yolk sac, there were significant increases in embryo survival in both the presence and absence of oxacillin. ECg-modified and unmodified, GFP-transformed EMRSA-16 bacteria were visualized within phagocytic cells in the circulation and yolk sac; pre-treatment with ECg also significantly increased induction of the respiratory burst and suppressed increases in IL-1β expression typical of infection with untreated EMRSA-16. We conclude that exposure to ECg prior to infection reduces the lethality of EMRSA-16, renders cells more susceptible to elimination by immune processes and compromises their capacity to establish an inflammatory response in comparison to non-exposed bacteria.

Diet, the gut microbiome, and epigenetics

Increasingly, the gut microbiome is implicated in the etiology of cancer, not only as an infectious agent but also by altering exposure to dietary compounds that influence disease risk. Whereas the composition and metabolism of the gut microbiome is influenced by diet, the gut microbiome can also modify dietary exposures in ways that are beneficial or detrimental to the human host. The colonic bacteria metabolize macronutrients, either as specialists or in consortia of bacteria, in a variety of diverse metabolic pathways. Microbial metabolites of diet can also be epigenetic activators of gene expression that may influence cancer risk in humans. Epigenetics involves heritable changes in gene expression via post-translational and post-transcriptional modifications. Microbial metabolites can influence epigenetics by altering the pool of compounds used for modification or by directly inhibiting enzymes involved in epigenetic pathways. Colonic epithelium is immediately exposed to these metabolites, although some metabolites are also found in systemic circulation. In this review, we discuss the role of the gut microbiome in dietary metabolism and how microbial metabolites may influence gene expression linked to colon cancer risk.

LC-MS/MS profiling of a mastic leaf phenol enriched extract and its effects on H2O2 and Aβ(25-35) oxidative injury in SK-B-NE(C)-2 cells

The development of polyphenol neuroprotective nutraceuticals useful for functional foods could be a valuable strategy for counteracting oxidative stress relative diseases as Alzheimer's Disease (AD). Oxidative stress is one of the AD earliest event and seems to play a central role in Aβ generation, neuroinflammation, and neuronal apoptosis. In order to counteract AD neurodegeneration, the inhibition of the vicious cycle of Aβ generation and oxidation is an attractive therapeutic strategy, and antiamyloidogenic and antioxidant plant drugs could represent an alternative and valid approach. In this context, an alcoholic extract (Pl-M) from deterpenated Pistacia lentiscus L. leaves was investigated for its phenol composition through LC-ESI-MS/MS analysis. Besides the identified metabolites, ten compounds were reported for the first time as constituents of Pistacia lentiscus leaves. Through DPPH, ABTS, and ORAC methods, the antioxidant potential of the extract was initially investigated. In order to evaluate the preparation of a safe and no toxic extract, MTT, SRB, and LDH assays toward SH-5YSY, and SK-N-BE(2)-C human neuronal cell lines, as well as on C6 mouse glial cell line, were performed. Evaluating the protective effects from oxidant injury in SK-N-BE(2)-C cells cotreated with the plant complex and H2O2, or Aβ(25-35) fragment, it was observed that Pl-M extract exerted a significant cytoprotective response in both the oxidized cell systems. In particular, Pl-M extract was able to reduce by nearly 50% the Aβ(25-35) induced toxicity at 25.0 μg/mL dose level, whereas it counteracted almost completely the cytotoxic action at 100.0 μg/mL. Data obtained allow us to hypothesize the use of Pistacia lentiscus leaves, a broadly available and renewable source, as an alternative strategy for the enrichment of food matrices with polyphenol bioactives. The present study put the basis for bioavailability and preclinical studies, able to define Pl-M extract safety and efficacy.

Nature and consequences of non-covalent interactions between flavonoids and macronutrients in foods

Many of the potential health benefits of flavonoids have been associated with their specific chemical and biological properties including their ability to interact and bind non-covalently to macronutrients in foods. While flavonoid-protein interactions and binding have been the subject of intensive study, significantly less is understood about non-covalent interactions with carbohydrates and lipids. These interactions with macronutrients are likely to impact both the flavonoid properties in foods, such as their radical scavenging activity, and the food or beverage matrix itself, including their taste, texture and other sensorial properties. Overall, non-covalent binding of flavonoids with macronutrients is primarily driven by van der Waals interactions. From the flavonoid perspective, these interactions are modulated by characteristics such as degree of polymerization, molecular flexibility, number of external hydroxyl groups, or number of terminal galloyl groups. From the macronutrient standpoint, electrostatic and ionic interactions are generally predominant with carbohydrates, while hydrophobic interactions are generally predominant with lipids and mainly limited to interactions with flavonols. All of these interactions are involved in flavonoid-protein interactions. While primarily associated with undesirable characteristics in foods and beverages, such as astringency, negative impact on macronutrient digestibility and hazing, more recent efforts have attempted to leverage these interactions to develop controlled delivery systems or strategies to enhance flavonoids bioavailability. This paper aims at reviewing the fundamental bases for non-covalent interactions, their occurrence in food and beverage systems and their impact on the physico-chemical, organoleptic and some nutritional properties of food.

Human studies on the absorption, distribution, metabolism, and excretion of tea polyphenols

Recent research on the bioavailability of flavan-3-ols after ingestion of green tea by humans is reviewed. Glucuronide, sulfate, and methyl metabolites of (epi)catechin and (epi)gallocatechin glucuronide reach peak nanomolar per liter plasma concentrations 1.6-2.3 h after intake, indicating absorption in the small intestine. The concentrations then decline, and only trace amounts remain 8 h after ingestion. Urinary excretion of metabolites over a 24-h period after green tea consumption corresponded to 28.5% of the ingested (epi)catechin and 11.4% of (epi)gallocatechin, suggesting higher absorption than that of most other flavonoids. The fate of (-)-epicatechin-3-O-gallate, the main flavan-3-ol in green tea, is unclear because it appears unmetabolized in low concentrations in plasma but is not excreted in urine. Possible enterohepatic recirculation of flavan-3-ols is discussed along with the impact of dose and other food components on flavan-3-ol bioavailability. Approximately two-thirds of the ingested flavan-3-ols pass from the small to the large intestine where the action of the microbiota results in their conversion to C-6-C-5 phenylvalerolactones and phenylvaleric acids, which undergo side-chain shortening to produce C-6-C-1 phenolic and aromatic acids that enter the bloodstream and are excreted in urine in amounts equivalent to 36% of flavan-3-ol intake. Some of these colon-derived catabolites may have a role in vivo in the potential protective effects of tea consumption. Although black tea, which contains theaflavins and thearubigins, is widely consumed in the Western world, there is surprisingly little research on the absorption and metabolism of these compounds after ingestion and their potential impact on health.

Dietary (poly)phenolics in human health: structures, bioavailability, and evidence of protective effects against chronic diseases

Human intervention trials have provided evidence for protective effects of various (poly)phenol-rich foods against chronic disease, including cardiovascular disease, neurodegeneration, and cancer. While there are considerable data suggesting benefits of (poly)phenol intake, conclusions regarding their preventive potential remain unresolved due to several limitations in existing studies. Bioactivity investigations using cell lines have made an extensive use of both (poly)phenolic aglycones and sugar conjugates, these being the typical forms that exist in planta, at concentrations in the low-μM-to-mM range. However, after ingestion, dietary (poly)phenolics appear in the circulatory system not as the parent compounds, but as phase II metabolites, and their presence in plasma after dietary intake rarely exceeds nM concentrations. Substantial quantities of both the parent compounds and their metabolites pass to the colon where they are degraded by the action of the local microbiota, giving rise principally to small phenolic acid and aromatic catabolites that are absorbed into the circulatory system. This comprehensive review describes the different groups of compounds that have been reported to be involved in human nutrition, their fate in the body as they pass through the gastrointestinal tract and are absorbed into the circulatory system, the evidence of their impact on human chronic diseases, and the possible mechanisms of action through which (poly)phenol metabolites and catabolites may exert these protective actions. It is concluded that better performed in vivo intervention and in vitro mechanistic studies are needed to fully understand how these molecules interact with human physiological and pathological processes.

Influence of formulation and processing on absorption and metabolism of flavan-3-ols from tea and cocoa

Flavan-3-ols are a major subclass of the class of plant phytochemicals known as flavonoids. Flavan-3-ols are commonly found in fruit, vegetable, and botanical products, including tea, cocoa, grapes, and apples. Both monomeric catechins and polymeric procyanidins are common in the diet, along with several derivatives produced by degradation of these species during processing. Both epidemiological and biological evidence suggests a health-protective role for dietary flavan-3-ols, leading to increased interest in the bioavailability of these compounds from foods. Flavan-3-ol bioavailability depends on numerous factors, including digestive release, absorption, metabolism, and elimination. In addition to these in vivo factors, the complexity of whole-food systems (physical form, flavan-3-ol form and dose, macronutrient and micronutrient profile, processing, etc.) influences the absorption efficiency and circulating profile of flavan-3-ols. An understanding of how food matrices may influence flavan-3-ol absorption will provide a framework to design and develop functional products that positively affect flavan-3-ol absorption and, by extension, potential bioactivity.

Epigallocatechin-3-gallate regulates cell growth, cell cycle and phosphorylated nuclear factor-κB in human dermal fibroblasts

AIM

To investigate the effects of (-)epigallocatechin-3-gallate (EGCG), the main polyphenol in green tea, on cell growth, cell cycle and phosphorylated nuclear factor-κB (pNF-κB) expression in neonatal human dermal fibroblasts (nHDFs).

METHODS

The proliferation and cell-cycle of nHDFs were determined using WST-8 cell growth assay and flow cytometry, respectively. The apoptosis was examined using DNA ladder and Annexin V-FITC assays. The expression levels of pNF-κB and cell cycle-related genes and proteins in nHDFs were measured using cDNA microarray analyses and Western blot. The cellular uptake of EGCG was examined using fluorescence (FITC)-labeled EGCG (FITC-EGCG) in combination with confocal microscopy.

RESULTS

The effect of EGCG on the growth of nHDFs depended on the concentration tested. At a low concentration (200 μmol/L), EGCG resulted in a slight decrease in the proportion of cells in the S and G(2)/M phases of cell cycle with a concomitant increase in the proportion of cells in G(0)/G(1) phase. At the higher doses (400 and 800 μmol/L), apoptosis was induced. The regulation of EGCG on the expression of pNF-κB was also concentration-dependent, whereas it did not affect the unphosphorylated NF-κB expression. cDNA microarray analysis showed that cell cycle-related genes were down-regulated by EGCG (200 μmol/L). The expression of cyclins A/B and cyclin-dependent kinase 1 was reversibly regulated by EGCG (200 μmol/L). FITC-EGCG was found to be internalized into the cytoplasm and translocated into the nucleus of nHDFs.

CONCLUSION

EGCG, through uptake into cytoplasm, reversibly regulated the cell growth and expression of cell cycle-related proteins and genes in normal fibroblasts.

Catechin, green tea component, causes caspase-independent necrosis-like cell death in chronic myelogenous leukemia

Management strategies of chronic phase chronic myelogenous leukemia (CML) have been revolutionized due to the discovery of a selective tyrosine kinase inhibitor, imatinib (Gleevec, STI571), which is substantially improving median survival. However, emergence of imatinib-resistance has put up a serious problem that requires novel treatment methods. Catechins, polyphenolic compounds in green tea, are gathering much attention due to their potential antitumor effects. So far (-)-epigallocatechin-3-gallate (EGCG), the most abundant component of catechin, has been shown to cause typical apoptosis in several tumor cell lines in most cases through activation of caspases. In this study, we showed that EGCG predominantly caused necrosis-like cell death via a caspase-independent mechanism in CML cells, K562 and C2F8, whereas imatinib induced the typical apoptotic cell death. Moreover, this caspase-independent cell death partially mediated the release of apoptosis-inducing factor, AIF, and serine protease, HtrA2/Omi, from the mitochondria to cytosol. In addition, EGCG enhanced the imatinib-induced cell death (P < 0.01) resulting in additive cell death in K562 cells and EGCG alone, effectively reduced the viability of imatinib-resistant K562 cells (P < 0.01). Catechin is a possible candidate for an antitumor agent that causes cell death in CML cells via a caspase-independent mechanism.

Tea catechins as inhibitors of receptor tyrosine kinases: mechanistic insights and human relevance

Receptor tyrosine kinases (RTKs) play important roles in the control of fundamental cellular processes, influencing the balance between cell proliferation and death. RTKs have emerged as molecular targets for the treatment of various cancers. Green tea and its polyphenolic compounds, the catechins, exhibit chemopreventive and chemotherapeutic properties in many human cancer cell types, as well as in various carcinogenicity models in vivo. Epidemiological studies are somewhat less convincing, but some positive correlations have been observed. The tea catechins, including (-)-epigallocatechin-3-gallate (EGCG), have pleiotropic effects on cellular proteins and signaling pathways. This review focuses on the ability of the tea constituents to suppress RTK signaling, and summarizes the mechanisms by which EGCG and other catechins might exert their protective effects towards dysregulated RTKs in cancer cells. The findings are discussed in the context of ongoing clinical trials with RTK inhibitors, and the possibility for drug/nutrient interactions enhancing therapeutic efficacy.

Absorption, metabolism, and excretion of green tea flavan-3-ols in humans with an ileostomy

Green tea containing 634 micromol of flavan-3-ols was ingested by human subjects with an ileostomy. Ileal fluid, plasma, and urine collected 0-24 h after ingestion were analysed by HPLC-MS. The ileal fluid contained 70% of the ingested flavan-3-ols in the form of parent compounds (33%) and 23 metabolites (37%). The main metabolites effluxed back into the lumen of the small intestine were O-linked sulphates and methyl-sulphates of (epi)catechin and (epi)gallocatechin. Thus, in subjects with a functioning colon substantial quantities of flavan-3-ols would pass from the small to the large intestine. Plasma contained 16 metabolites, principally methylated, sulphated, and glucuronidated conjugates of (epi)catechin and (epi)gallocatechin, exhibiting 101-256 nM peak plasma concentration and the time to reach peak plasma concentration ranging from 0.8 to 2.2 h. Plasma pharmacokinetic profiles were similar to those obtained with healthy subjects, indicating that flavan-3-ol absorption occurs in the small intestine. Ileostomists had earlier plasma time to reach peak plasma concentration values than subjects with an intact colon, indicating the absence of an ileal brake. Urine contained 18 metabolites of (epi)catechin and (epi)gallocatechin in amounts corresponding to 6.8+/-0.6% of total flavan-3-ol intake. However, excretion of (epi)catechin metabolites was equivalent to 27% of the ingested (-)-epicatechin and (+)-catechin.

Laboratory, epidemiological, and human intervention studies show that tea (Camellia sinensis) may be useful in the prevention of obesity

Tea (Camellia sinensis, Theaceae) and tea polyphenols have been studied for the prevention of chronic diseases, including obesity. Obesity currently affects >20% of adults in the United States and is a risk factor for chronic diseases such as type II diabetes, cardiovascular disease, and cancer. Given this increasing public health concern, the use of dietary agents for the prevention of obesity would be of tremendous benefit. Whereas many laboratory studies have demonstrated the potential efficacy of green or black tea for the prevention of obesity, the underlying mechanisms remain unclear. The results of human intervention studies are mixed and the role of caffeine has not been clearly established. Finally, there is emerging evidence that high doses of tea polyphenols may have adverse side effects. Given that the results of scientific studies on dietary components, including tea polyphenols, are often translated into dietary supplements, understanding the potential toxicities of the tea polyphenols is critical to understanding their potential usefulness in preventing obesity. In this review, we will critically evaluate the evidence for the prevention of obesity by tea, discuss the relevance of proposed mechanisms in light of tea polyphenol bioavailability, and review the reports concerning the toxic effects of high doses of tea polyphenols and the implication that this has for the potential use of tea for the prevention of obesity. We hope that this review will expose areas for further study and encourage research on this important public health issue.

(—)-Epigallocatechin gallate (EGCG) prevents isoprenaline-induced cardiac toxicity by stabilizing cardiac marker enzymes and membrane-bound ATPases

Intake of tea flavonoids has been reported to reduce the incidence of cardiovascular disease. The present study was undertaken to investigate the preventive effect of (—)epigallocatechin gallate (EGCG) on heart weight, cardiac marker enzymes, membrane-bound ATPases and electrolytes in isoprenaline (ISO)-induced myocardial infarcted (MI) Wistar rats. Rats subcutaneously administered ISO 100 mgkg−1 at intervals of 24 h for 2 days resulted in significant increases in heart weight and the activities of cardiac marker enzymes such as creatine kinase, creatine kinase-MB, lactate dehydrogenase (LDH), aspartate transaminase and alanine transaminase in serum, and significant decreases in the activities of these enzymes in the myocardium. ISO injection also increased levels of LDH isoenzymes (LDH 1 and LDH 2). The activity of Na+/K+ ATPase was decreased significantly and the activities of Ca2+ and Mg2+ ATPases were increased significantly in ISO-induced MI rats. Furthermore, the levels of potassium were lowered and the levels of sodium and calcium were increased in ISO-induced MI rats. Prior treatment with EGCG (10, 20 and 30 mgkg−1) daily for a period of 21 days reduced the effects of ISO on heart weight, activities of cardiac marker enzymes and membrane bound-ATPases and levels of LDH 1 and LDH 2 and electrolytes. Thus, EGCG exhibits beneficial effects on these enzymes and electrolytes. The observed effects may be due to the antioxidant and membrane-stabilizing effects of EGCG in ISO-induced MI rats.

Inhibition of mutagenic PhIP formation by epigallocatechin gallate via scavenging of phenylacetaldehyde

Chemical model investigation showed that both epigallocatechin gallate (EGCG) and its peracetate, which has all the hydroxyl groups acetylated, effectively reduced the formation of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), the most abundant mutagenic heterocyclic amine found in foods. Mechanistic study was subsequently carried out to characterize the probable inhibitory mechanism involved. GC-MS analysis showed that EGCG in only one-fourth molar quantity of phenylalanine reduced formation of phenylacetaldehyde, a key PhIP intermediate by nearly 90%. Its peracetate also showed similar inhibitory activity. This further supported the existence of an antioxidant-independent mechanism contributing to the inhibition of PhIP formation by EGCG. Subsequent LC-MS analyses of samples from a wide range of model systems consisting of PhIP precursors showed the generation of characteristic analytes with molecular weight corresponding to the sum of EGCG and phenylalanine fragment(s) only in models where phenylalanine and EGCG were simultaneously present. An isotope-labeling study revealed that these analytes all contained fragment(s) of phenylalanine origin. Direct reaction employing phenylacetaldehyde and EGCG further confirmed the capability of EGCG to form adducts with phenylacetaldehyde, thus reducing its availability for PhIP formation. Finally, an investigation of the time course of the generation of postulated adduction products supported EGCG as an effective inhibitor of PhIP formation in prolonged heating processes.

Formulation and characterization of polyphenol-loaded lipid nanocapsules

The purpose of this study was to design and characterize two flavonoid-loaded lipid nanocapsules (LNC) by applying the phase inversion process, and to enhance their apparent solubility and/or the stability. The flavonoid-loaded LNC were characterized by particle size, encapsulation efficiency, drug leakage rates, stability and spectroscopic studies. It was observed that quercetin-loaded LNC30 (3%) and LNC60 (2%) carried a particle size of 30.3 and 55.1 nm, respectively and significant higher entrapment efficiency. Encapsulation of quercetin (QC) in LNC enabled us to increase its apparent aqueous solubility by a factor of 100. And in view of calculations and results, it seems most probable that QC is arranged at this LNC interface between the oil phase and the hydrophilic polyethylene glycol moieties of the surfactant. In addition, colloidal suspensions proved to be stable in term of encapsulation for at least 10 weeks and QC was not oxidised. With simple chemical modification of (-)-epigallocatechin-3-gallate or (-)-EGCG, it was possible to reach very high encapsulation rates (95%). Thus we obtained stable colloidal suspensions of (-)-EGCG in water over 4 weeks while free (-)-EGCG solubilised in water exhibited 100% degradation within 4h. The initial problems (solubility and stability) of these flavonoids were resolved thanks to drug-loaded LNC.