stilbenes and morin

Diabetes is characterized by the development of endothelial dysfunction, which affects both nitric oxide (NO)-mediated relaxation and endothelium-derived contracting factors, associated with vascular oxidative stress. There is a growing body of evidence suggesting that polyphenols have several beneficial effects, such as antioxidant and anti-inflammatory activities. This study investigated whether short-term treatment with polyphenols (chlorogenic acid (CA), morin (MO), resveratrol (RV)) can improve endothelial dysfunction related to diabetes. Aorta reactivity was determined in organ chambers, and we measured NO production and thromboxane B2 (TXB2; a metabolite of TXA2) from aortas in response to acetylcholine (ACh). Streptozotocin (STZ)-induced diabetic mice (16 weeks) were injected with solvent (ethanol, 10% v/v; intraperitoneally (i.p.)), CA (0.03 mmol/kg/d), MO (0.03 mmol/kg/d), and RV (0.03 mmol/kg/d) for 5 d. The ACh-induced endothelium-dependent relaxation was markedly reduced in rings of STZ-induced diabetic mice compared to controls. The treatment with polyphenols (significantly: MO, tendency: CA and RV) for only 5 d improved the NO components of relaxation, but did not normalize ACh-stimulated NO production. However, polyphenol treatment suppressed the ACh-stimulated level of TXB2 in aortas from STZ-induced diabetic mice. Thus, treatment with polyphenols caused basal NO production and a prompt improvement of the endothelial function in diabetic mice, and this may involve the normalization of TXA2 levels, not NO production, under ACh stimulation.

Topics: Animals; Antioxidants; Aorta, Thoracic; Chlorogenic Acid; Diabetes Mellitus, Experimental; Endothelium-Dependent Relaxing Factors; Endothelium, Vascular; Flavonoids; Isometric Contraction; Male; Mice, Inbred ICR; Muscle, Smooth, Vascular; Nitric Oxide; Oxidative Stress; Polyphenols; Resveratrol; Stilbenes; Streptozocin; Thromboxane A2

The paper described a novel chromatographic method for the simultaneous determination of phenolic compounds such as gallic, protocatechuic, vanillic, caffeic, syringic, p-coumaric and salicylic acid, (+)-catechin, (‒)-epicatechin, rutin, morin, quercetin, coumarin and trans-resveratrol at their maximum absorbance wavelengths (MAW) employing reverse-phase high performance liquid chromatography combined with DAD and UV detection via detection wavelength switching. The method was based on MAW acquisition by DAD and quantification by UV. The separation process was performed on a Shim-Pack VP-ODS C18 column (250 mm × 4.6 mm, 5 μm) held at 30 °C, utilizing 3.0% acetic acid and acetonitrile as mobile phase at a flow rate of 0.8 mL/min in the gradient elution mode. The method was fully validated in terms of linearity (r2 > 0.9990, 10‒350 mg/L), precision (both intra-day and inter-day RSD < 4.22%), accuracy (97.31%‒104.66%), specificity, robustness (0.59% < RSD < 2.86%), limit of detection and quantification. The switching method significantly improved the sensitivities of most phenolics studied in comparison with the standard constant wavelength detection (280 nm). The proposed method has been successfully applied to the determination of 14 phenolic compounds in 89 varieties of one-year-old Chinese grape one-year-canes. Grape canes contain many phenolics, especially trans-resveratrol, (‒)-epicatechin, and (+)-catechin.

Topics: Catechin; Chromatography, High Pressure Liquid; Coumarins; Flavonoids; Phenols; Quercetin; Resveratrol; Stilbenes; Ultraviolet Rays; Vitis

Altered immune function during ageing results in increased production of nitric oxide (NO) and other inflammatory mediators. Recently, we have reported that NO production was inhibited by naturally-occurring proteasome inhibitors (quercetin, δ-tocotrienol, and riboflavin) in lipopolysaccharide (LPS)-stimulated RAW264.7 cells, and thioglycolate-elicited peritoneal macrophages from C57BL/6 mice. In a continuous effort to find more potent, non-toxic, commercially available, naturally-occurring proteasome inhibitors that suppress inflammation, the present study was carried out to describe the inhibition of NF-κB activation and NO, TNF-α, IL-6, IL-1β, and iNOS expression by trans-resveratrol, trans-pterostilbene, morin hydrate, and nicotinic acid in LPS-induced RAW 264.7 cells and thioglycolate-elicited peritoneal macrophages from C57BL/6 and BALB/c mice.. The present results indicate that resveratrol, pterostilbene, and morin hydrate caused significant inhibition (>70% to 90%; P < 0.02) in the activities of chymotrypsin-like, trypsin-like, and post-acidic (post-glutamase) proteasome sites in RAW 264.7 cells at a dose of only 20 μM. These compounds also inhibited the production of NO by RAW-264.7 cells stimulated with LPS alone (>40%; P < 0.05), or LPS + interferon-γ (IFN-γ; >60%; P < 0.02). Furthermore, resveratrol, pterostilbene, morin hydrate, and quercetin suppressed secretion of TNF-α (>40%; P < 0.05) in LPS-stimulated RAW 264.7 cells, and suppressed NF-κB activation (22% to 45%; P < 0.05) in LPS-stimulated HEK293T cells. These compounds also significantly suppressed LPS-induced expression of TNF-α, IL-1β, IL-6, and iNOS genes in RAW 264.7 cells, and also in thioglycolate-elicited peritoneal macrophages from C57BL/6 and BALB/c mice.. The present results clearly demonstrate that resveratrol and pterostilbene are particularly potent proteasome inhibitors that suppress expression of genes, and production of inflammatory products in LPS-stimulated RAW 264.7 cells, and macrophages from C57BL/6 and BALB/c mice. Resveratrol and pterostilbene which are present in grapes, blueberries, and red wine, have been implicated as contributing factors to the lower incidence of cardiovascular disease in the French population, despite their relatively high dietary fat intake. Consequently, it appears likely that the beneficial nutritional effects of resveratrol and pterostilbene are due at least in part, to their ability to inhibit NF-κB activation by the proteasome, thereby suppressing activation of pro-inflammatory cytokines and iNOS genes, resulting in decreased secretion of TNF-α, IL-1β, IL-6, and NO levels, in response to inflammatory stimuli. This is the first report demonstrating that resveratrol and pterostilbene act as proteasome inhibitors, thus providing a mechanism for their anti-inflammatory effects.

Topics: Animals; Cell Line; Cytokines; Enzyme Inhibitors; Flavonoids; Lipopolysaccharides; Macrophages; Mice; Mice, Inbred BALB C; Mice, Inbred C57BL; NF-kappa B; Nitric Oxide; Resveratrol; Stilbenes; Tumor Necrosis Factor-alpha