Flavonoid constituents in the leaves of Myrica rubra sieb. et zucc. with anti-inflammatory activity

The leaves of Myrica rubra sieb. et zucc. have been used in oriental traditional medicine for the treatment of burns, skin diseases, and as an antidiarrheal in China, Japan, and Korea. Activity guided isolation of the leaves of M. rubra has led to the isolation of five flavonoid: myricetin (1), myricitrin (2), myricetin 3-O-(2″-O-galloyl)-α-L-rhamnopyranoside (3), myricetin 3-O-(2″-O-galloyl)-β-D-galactopyranoside (4), and quercetin 3-O-(2″-O-galloyl)-β-D-galactopyranoside (5). All isolates were evaluated for their antioxidant potency against the superoxide anion (O2−), and compounds 3–5 showed potent scavenging activities with 50 % inhibition concentration (IC50) values compared to the positive control, allopurinol. Compounds 1–5 were evaluated as inhibitors of various macrophage functions involved in the inflammatory process. These five compounds significantly and dose dependently inhibited lipopolysaccharide (LPS)-stimulated nitric oxide (NO), pro-inflammatory cytokines, and the protein levels of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) in LPS-stimulated RAW 264.7 macrophages. Our results suggest that galloyl flavonol glycosides (3–5) isolated from M. rubra might be beneficial for the treatment of inflammation‐related diseases.