Flavonoids from the leaves of Apocynum venetum and their anti-inflammatory activity

Chemical investigation of the EtOAc-soluble extract of the leaves of Apocynum venetum allowed the isolation of seven flavonoids including a new compound named 4'-hydroxy-7-O-(4-hydroxybenzyl)-3-methoxy-6-prenylflavone (I) and six known compounds (2-7). The structures of these compounds are elucidated by spectroscopic and physico-chemical analyses. All the isolates are evaluated for in vitro anti-inflammatory activity by measuring their inhibitory activities on nitric oxide and tumor necrosis factor-a production in lipopolysaccharide-induced mouse peritoneal macrophages (RAW 264.7). Among them, 5 exhibits significant inhibitory activity toward nitric oxide and tumor necrosis factor-alpha production with IC50 values of 9.0 +/- 0.7 and 42.1 +/- 0.8 mu M, respectively. In addition, I also shows moderate inhibitory activity toward nitric oxide production with an IC50 value of 17.2 +/- 0.9 mu M.