Antioxidative and anti-inflammatory effect of quercetin and its glycosides isolated from mampat (Cratoxylum formosum)

In this study, quercetin, quercetin-3-O-beta-d-glucopyranoside (isoquercitrin), quercetin-3-O-beta-d-galactopyranoside (hyperin), and quercertin-3-O-alpha-l-rhamnoside (quercitrin) from mampat (Cratoxylum formosum) were isolated and their antioxidative and anti-inflammatory activities were investigated. Quercetin displayed weaker antioxidant activity than its glycosides, while the cellular antioxidant capacity of quercetin and hyperin was stronger than that of isoquercitrin and quercitrin, indicating that the higher cell-membrane permeability of quercetin and hyperin than isoquercitrin and quercitrin was due to the different hydrophobicity and the specific membrane receptor for galactose. The anti-inflammatory activity of quercetin was shown to be higher to its glycosides in nitric oxide (NO) production, inducible nitric oxide synthase (iNOS) expression, and nuclear factor (NF)-kappa B activation, suggesting that quercetin inhibits NO production in LPS-stimulated RAW 264.7 cells via control of iNOS expression with attenuation of NF-kappa B activation. The data obtained in this study illustrates that the presence and kind of monosaccharide in quercetin glycosides may play a critical role in their cellular antioxidant and anti-inflammatory activities.