Burdock (Arctium lappa L.) leaf flavonoids rich in morin and quercetin 3-O-rhamnoside ameliorate lipopolysaccharide-induced inflammation and oxidative stress in RAW264.7 cells

In this study, the anti-inflammatory and antioxidant activities and mechanism of burdock leaf flavonoids (BLF) on LPS-stimulated inflammation in RAW264.7 macrophage cells were explored. We have observed that BLF and main effective components morin and quercetin 3-O-rhamnoside pretreatment significantly inhibited LPS-stimulated inflammatory activation of RAW264.7 cells by lowering the levels of NO, PGE2, TNF-alpha, and IL-6 production (p < .05). At the same time, BLF not only had potent free radical scavenging ability in vitro (DPPH: 2025.33 +/- 84.15 mu mol Trolox/g, ABTS: 159.14 +/- 5.28 mu mol Trolox/g, and ORAC: 248.72 +/- 9.74 mu mol Trolox/g) but also effectively ameliorated cellular oxidative stress status by restoring the decreased activity of antioxidant enzymes (SOD, CAT, and GSH-Px) and decreasing the elevated levels of ROS and TBARS in LPS-stimulated macrophages (p < .05). The western blot analysis indicated that BLF and main components morin and quercetin 3-0-rhamnoside mainly inhibited LPS-stimulated inflammation by reducing the iNOS and COX-2 protein expression, decreasing cellular ROS, and blocking the activation of NE-kappa B signaling pathway in macrophages. Our results collectively imply that BLF could be used as a new type of functional factor for the development of antioxidant and anti-inflammatory foods.