The flavanol (-)-epicatechin and its metabolites protect against oxidative stress in primary endothelial cells via a direct antioxidant effect

The contribution of the major metabolite 4′-O-methylmonoHER to the antioxidant activity of the flavonoid monoHER

“…For several flavonoids it is known that metabolites of these flavonoids contribute to their effect [19]. In this respect, much attention is given to O-methylated metabolites that are more readily taken up than the parent flavonoid, have an improved metabolic stability and display biological activity [21], as demonstrated for the 4 0 O-methyl metabolite of quercetin [20].…”

Direct Effects of (−)-Epicatechin and Procyanidin B2 on the Respiration of Rat Heart Mitochondria

“…There is accumulating evidence that (−)-epicatechin and its derivatives have significant role in prevention of cardiovascular diseases in humans [5]. Potent antioxidant action, modulation of cell signalling, stabilization of membranes, improvement of endothelial function, reduction of the blood pressure, and protection of mitochondria, main organelles responsible for cellular energy supply, are being proposed as possible mechanisms of beneficial effects of (−)-epicatechin [4].…”

The influence of phase II conjugation on the biological activity of flavonoids

“…In contrast, sulfation is reported to further increase of H 2 O 2 induced heme oxygenasegene expression in HUVEC [86]. Glucuronidation is reported to reduce the ability of quercetin to protect cells from oxidative stress in vitro, while methylation is reported to not affect the activity of quercetin on the protection of H9c2 cardiomyocytes against hydrogen peroxide.…”

“…It is presumed that flavonoid aglycones can enter cells through passive diffusion, while many flavonoid conjugates, especially glucuronides, have to rely on active transport into the cells [86,87]. Active cellular uptake of flavonoid conjugates appears to be affected by the conjugation position [88] and it has been shown in vitro for certain cell types, e.g.…”

“…Flavonoid glucuronides can also be deglucuronidated extracellularly by β-glucuronidase released from neutrophils and macrophages, and the activity of extracellular β-glucuronidases is reported to be higher during inflammation, which leads to higher concentrations of flavonoid aglycones at sites of inflammation [86,90,91].…”