Numerous studies have demonstrated the importance of naturally occurring dietary polyphenols in promoting cardiovascular health and emphasized the significant role these compounds play in limiting the effects of cellular aging. Polyphenols such as resveratrol, epigallocatechin gallate (EGCG), and curcumin have been acknowledged for having beneficial effects on cardiovascular health, while some have also been shown to be protective in aging. This review highlights the literature surrounding this topic on the prominently studied and documented polyphenols as pertaining to cardiovascular health and aging.
(-)-Epigallocatechin gallate (EGCG) is a major polyphenol component of green tea that has antioxidant activities. Lipopolysaccharide (LPS) induces inflammatory cytokine production and impairs blood-brain barrier (BBB) integrity. We examined the effect of EGCG on LPS-induced expression of the inflammatory cytokines in human cerebral microvascular endothelial cells (hCMECs) and BBB permeability.
Catechins (flavan-3-ols), the most important secondary metabolites in the tea plant, have positive effects on human health and are crucial in defense against pathogens of the tea plant. The aim of this study was to elucidate the biosynthetic pathway of galloylated catechins in the tea plant. The results suggested that galloylated catechins were biosynthesized via 1-O-glucose ester-dependent two-step reactions by acyltransferases, which involved two enzymes, UDP-glucose: galloyl-1-O-β-D-glucosyltransferase (UGGT) and a newly discovered enzyme, epicatechin:1-O-galloyl-β-D-glucose O-galloyltransferase (ECGT). In the first reaction, the galloylated acyl donor β-glucogallin was biosynthesized by UGGT from gallic acid and uridine diphosphate glucose. In the second reaction, galloylated catechins were produced by ECGT catalysis from β-glucogallin and 2,3-cis-flavan-3-ol. 2,3-cis-flavan-3-ol and 1-O-galloyl-β-D-glucose were appropriate substrates of ECGT rather than 2,3-trans-flavan-3-ol and 1,2,3,4,6- pentagalloylglucose. Purification by more than 1641-fold to apparent homogeneity yielded ECGT with an estimated molecular mass of 241 to 121 kDa by gel filtration. Enzyme activity and SDS-PAGE analysis indicated that the native ECGT might be a dimer, trimer or tetramer of 60 and/or 58 kDa monomers, and these monomers represent a heterodimer consisting of pairs of 36- or 34-, and 28-kDa subunits. MALDI-TOF-TOF MS showed that the protein SCPL1199 was identified. Epigallocatechin and epicatechin exhibited higher substrate affinities than β-glucogallin. ECGT had an optimum temperature of 30 and maximal reaction rates between pH 4.0 and 6.0. The enzyme reaction was inhibited dramatically by phenylmethylsulfonyl fluoride, HgCl2, and sodium deoxycholate.
Cranberry consumption has shown prophylactic effects against urinary tract infections (UTI), although the mechanisms involved are not completely understood. In this paper, cranberry phenolic compounds and their potential microbial-derived metabolites (such as simple phenols and benzoic, phenylacetic and phenylpropionic acids) were tested for their capacity to inhibit the adherence of uropathogenic Escherichia coli (UPEC) ATCC®53503™ to T24 epithelial bladder cells. Catechol, benzoic acid, vanillic acid, phenylacetic acid and 3,4-dihydroxyphenylacetic acid showed anti-adhesive activity against UPEC in a concentration-dependent manner from 100-500 µM, whereas procyanidin A2, widely reported as an inhibitor of UPEC adherence on uroepithelium, was only statistically significant (p < 0.05) at 500 µM (51.3% inhibition). The results proved for the first time the anti-adhesive activity of some cranberry-derived phenolic metabolites against UPEC in vitro, suggesting that their presence in the urine could reduce bacterial colonization and progression of UTI.
Osteopontin (OPN) promotes hepatic fibrosis, and developing therapies targeting OPN expression in settings of hepatic injury holds promise. The polyphenol epigallocatechin-3-gallate (EGCG), found in high concentrations in green tea, downregulates OPN expression through OPN mRNA degradation, but the mechanism is unknown. Previous work has shown that microRNAs can decrease OPN mRNA levels, and other studies have shown that EGCG modulates the expression of multiple microRNAs. In our study, we first demonstrated that OPN induces hepatic stellate cells to transform into an activated state. We then identified three microRNAs which target OPN mRNA: miR-181a, miR-10b, and miR-221. In vitro results show that EGCG upregulates all three microRNAs, and all three microRNAs are capable of down regulating OPN mRNA when administered alone. Interestingly, only miR-221 is necessary for EGCG-mediated OPN mRNA degradation and miR-221 inhibition reduces the effects of EGCG on cell function. In vivo experiments show that thioacetamide (TAA)-induced cell cytotoxicity upregulates OPN expression; treatment with EGCG blocks the effects of TAA. Furthermore, chronic treatment of EGCG in vivo upregulates all three microRNAs equally, suggesting that in more chronic treatment all three microRNAs are involved in modulating OPN expression. We conclude that in in vitro and in vivo models of TAA-induced hepatic fibrosis, EGCG inhibits OPN-dependent injury and fibrosis. EGCG works primarily by upregulating miR-221 to accelerate OPN degradation. EGCG may therefore have utility as a protective agent in settings of liver injury.
Evidence continues to demonstrate the role of obesity in prostate carcinogenesis and prognosis, underscoring the need to identify and continue to evaluate the effective interventions to reduce obesity in populations at high risk. The aim of the study was to determine the effect of daily consumption of decaffeinated green tea catechins (GTC) formulation (Polyphenon E® (PolyE)) for 1 year on biomarkers of obesity in men who are at high risk for prostate cancer.
Tea is the world’s oldest and most popular caffeine-containing beverage with immense economic, medicinal, and cultural importance. Here, we present the first high-quality nucleotide sequence of the repeat-rich (80.9%), 3.02-Gb genome of the cultivated tea tree Camellia sinensis. We show that an extraordinarily large genome size of tea tree is resulted from the slow, steady, and long-term amplification of a few LTR retrotransposon families. In addition to a recent whole-genome duplication event, lineage-specific expansions of genes associated with flavonoid metabolic biosynthesis were discovered, which enhance catechin production, terpene enzyme activation, and stress tolerance, important features for tea flavor and adaptation. We demonstrate an independent and rapid evolution of the tea caffeine synthesis pathway relative to cacao and coffee. A comparative study among 25 Camellia species revealed that higher expression levels of most flavonoid- and caffeine- but not theanine-related genes contribute to the increased production of catechins and caffeine and thus enhance tea-processing suitability and tea quality. These novel findings pave the way for further metabolomic and functional genomic refinement of characteristic biosynthesis pathways and will help develop a more diversified set of tea flavors that would eventually satisfy and attract more tea drinkers worldwide.
Aim: The therapeutic potential of epigallocatechin-3-gallate (EGCG), a green tea polyphenol with anticancer properties, is limited by its inability to specifically reach tumors following intravenous administration. The purpose of this study was to determine whether a tumor-targeted vesicular formulation of EGCG would suppress the growth of A431 epidermoid carcinoma and B16-F10 melanoma in vitro and in vivo. Materials & methods: Transferrin-bearing vesicles encapsulating EGCG were administered intravenously to mice bearing subcutaneous A431 and B16-F10 tumors. Results: The intravenous administration of EGCG encapsulated in transferrin-bearing vesicles resulted in tumor suppression in 40% of A431 and B16-F10 tumors. Animal survival was improved by more than 20 days compared with controls. Conclusion: Encapsulation of EGCG in transferrin-bearing vesicles is a promising therapeutic strategy. Original submitted 28 November 2011; Revised submitted 11 May 2012; Published online 14 August 2012.
Green tea catechins have been hypothesized to increase energy expenditure and fat oxidation by inhibiting catechol-O-methyltransferase (COMT) and thus promoting more sustained adrenergic stimulation. Metabolomics may help to clarify the mechanisms underlying their putative physiological effects.
Although previous literature has reported that regular green tea consumption may improve blood pressure, the evidence from these studies is not consistent. The present study systematically reviewed randomised controlled trials and examined the effect of green tea consumption on blood pressure using meta-analysis.