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‐α, 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 μmol Trolox/g, ABTS: 159.14 ± 5.28 μmol Trolox/g, and ORAC: 248.72 ± 9.74 μmol 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‐O‐rhamnoside mainly inhibited LPS‐stimulated inflammation by reducing the iNOS and COX‐2 protein expression, decreasing cellular ROS, and blocking the activation of NF‐κB 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.