Anti-inflammatory actions of green tea catechins and ligands of peroxisome proliferator-activated receptors

The effect of adiponectin in the pathogenesis of non-alcoholic fatty liver disease (NAFLD) and the potential role of polyphenols in the modulation of adiponectin signaling

Non-alcoholic fatty liver disease (NAFLD) is one of the most common chronic liver diseases worldwide, as it affects up to 30 % of adults in Western countries. Moreover, NAFLD is also considered an independent risk factor for cardiovascular diseases. Insulin resistance and inflammation have been identified as key factors in the pathophysiology of NAFLD. Although the mechanisms associated with the development of NAFLD remain to be fully elucidated, a complex interaction between adipokines and cytokines appear to play a crucial role in the development of this condition. Adiponectin is the most common adipokine known to be inversely linked with insulin resistance, lipid accumulation, inflammation and NAFLD. Consequently, the focus has been on the use of new therapies that may enhance hepatic expression of adiponectin downstream targets or increase the serum levels of adiponectin in the treatment NAFLD. While currently used therapies show limited efficacy in this aspect, accumulating evidence suggest that various dietary polyphenols may stimulate adiponectin levels, offering potential protection against the development of insulin resistance, inflammation and NAFLD as well as associated conditions of metabolic syndrome. As such, this review provides a better understanding of the role polyphenols play in modulating adiponectin signaling to protect against NAFLD. A brief discussion on the regulation of adiponectin during disease pathophysiology is also covered to underscore the potential protective effects of polyphenols against NAFLD. Some of the prominent polyphenols described in the manuscript include aspalathin, berberine, catechins, chlorogenic acid, curcumin, genistein, piperine, quercetin, and resveratrol.

Assessment of preclinical effect of (+)-catechin hydrate on sexual function: An in silico and in vivo study

Considering dopamine-enhancing effect of (+)-catechin, the present study was designed to evaluate dopamine-2 (D2) receptor agonistic and phosphodiesterase-5 (PDE5) enzyme inhibitory effects in in silico and effect on male sexual function of Sprague Dawley rats in vivo. (+)-Catechin and standard (sildenafil and bromocriptine) were docked using Autodock Vina 1.1.2 and visualised by UCSF Chimera 1.14. Significant interactions in terms of binding energies were observed for catechin with both proteins. In in vivo study, the rats were dosed orally for 54 days with (+)-catechin hydrate (50 mg/kg), sildenafil citrate (standard, 4 mg/kg) and carboxymethylcellulose (vehicle, 0.25% w/v). The aphrodisiac effects were evaluated on the day 14, 28, 42 and 54 using the behavioural parameters of mounting and intromission. After the study, animals were sacrificed and testes and spermatozoa were assessed for safety profile. Results showed a significant increase in mount and intromission frequencies and a significant reduction in mount and intromission latencies in the catechin group on all tested days when compared to vehicle control. (+)-Catechin was found to be safe on histology of testes, sperm count, sperm motility and sperm morphology parameters. In conclusion, catechin demonstrated an enhancement in sexual behaviour without eliciting toxicity on the male reproductive system in rats.

Stabilization of Natural Antioxidants by Silk Biomaterials

The stabilities of three natural antioxidants, vitamin C (VC), (-)-epigallocatechin gallate (EGCG), and curcumin, in silk films were examined and mechanisms of stabilization were elucidated. The antioxidants were physically incorporated into three types of silk films: as-cast, dried from hydrogels, and methanol-treated. Films were stored at 4, 37, and 45 °C for 30 days in phosphate-buffered saline, pH 7.4, along with controls consisting of free antioxidants. Incorporation of antioxidants did not significantly change film morphology or secondary structure. When stored at 4 °C, all samples showed similar antioxidant activities (percent scavenging) at different time points, determined by the colorimetric 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay. At higher temperatures, VC in the as-cast film, EGCG in the as-cast and dried hydrogel films, and curcumin in the methanol-treated films retained more than 50% scavenging activity after 14 days of storage, significantly higher than the other samples. Interaction between antioxidants and silk, as well as degradation of the antioxidants, was investigated by fast-performance liquid chromatography (FPLC) and high-pressure liquid chromatography (HPLC), with an aim of understanding the mechanisms of silk-based stabilization. Binding of antioxidant molecules to hydrophobic or to hydrophilic/hydrophilic boundary regions of silk, depending on the chemical properties of the antioxidant, may account for the observed stabilization effects. The data can help guide further engineering of antioxidant-functionalized silk biomaterials.

Interaction of environmental moisture with powdered green tea formulations: effect on catechin chemical stability

Green tea and tea catechins must be stable in finished products to deliver health benefits; however, they may be adversely affected by tea processing/storage conditions and the presence of other components. The objective of this study was to determine the effects of storage relative humidity (RH) and addition of other ingredients on catechin stability in simulated dry beverage mixtures. Samples of green tea powder alone and mixed with sucrose, citric acid, and/or ascorbic acid were prepared and stored in desiccators at 22 degrees C and 0-85% RH for up to 3 months. Epicatechin, epigallocatechin, epicatechin gallate, and epigallocatechin gallate were determined by high-performance liquid chromatography (HPLC). Formulation and the interaction of formulation and RH significantly promoted catechin degradation ( P < 0.0001). The chemical degradation of total and individual catechins in green tea powder formulations was significantly increased ( P < 0.0001) by exposure to increasing RH, and the degradation was exacerbated at > or = 58% RH by the presence of powdered citric acid and at > or = 75% RH by the presence of ascorbic acid. Catechins degraded the most in formulations containing both acids. Although catechin chemical stability was maintained at < or = 43% RH in all samples stored at 22 degrees C for 3 months, caking was observed in samples at these relative humidities. These results are the first to demonstrate that addition of other dry components to tea powders may affect catechin stability in finished dry blends and highlight the importance of considering the complex interplay between a multicomponent system and its environment for developing stable products.