title: Structural requirements of flavonoids for nitric oxide production inhibitory activity and mechanism of action.
abstract: To clarify the structure-activity relationships of flavonoids for nitric oxide (NO) production inhibitory activity, we examined the inhibitory effects of 73 flavonoids on NO production in lipopolysaccharide-activated mouse peritoneal macrophages. Among those flavonoids, apigenin (IC(50)=7.7 microM), diosmetin (8.9 microM), and tetra-O-methylluteolin (2.4 microM), and hexa-O-methylmyricetin (7.4 microM) were found to show potent inhibitory activity, and the results suggested the following structural requirements of flavonoids: (1) the activities of flavones were stronger than those of corresponding flavonols; (2) the glycoside moiety reduced the activity; (3) the activities of flavones were stronger than those of corresponding flavanones; (4) the flavones and flavonols having the 4'-hydroxyl group showed stronger activities than those lacking the hydroxyl group at the B ring and having the 3',4'-dihydroxyl group; (5) the flavonols having the 3',4'-dihydroxyl group (catechol type) showed stronger activities than those having the 3',4',5'-trihydroxyl group (pyrogallol type); (6) the 5-hydroxyl group tended to enhance the activity; (7) methylation of the 3-, 5-, or 4'-hydroxyl group enhanced the activity; (8) the activities of isoflavones were weaker than those of corresponding flavones; (9) methylation of the 3-hydroxyl group reduced the cytotoxicity. In addition, potent NO production inhibitors were found to inhibit induction of inducible nitric oxide synthase (iNOS) without iNOS enzymatic inhibitory activity.
authors.affiliation: Kyoto Pharmaceutical University, Misasagi, Yamashina-ku, Kyoto 607-8412, Japan.
authors.forename: Hisashi
authors.initials: H
authors.lastname: Matsuda
authors.forename: Toshio
authors.initials: T
authors.lastname: Morikawa
authors.forename: Shin
authors.initials: S
authors.lastname: Ando
authors.forename: Iwao
authors.initials: I
authors.lastname: Toguchida
authors.forename: Masayuki
authors.initials: M
authors.lastname: Yoshikawa
mesh_terms: D000818:Animals; D005419:Flavonoids / Q000737:chemistry* / Q000494:pharmacology; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism; D008297:Male; D051379:Mice; D009569:Nitric Oxide / Q000037:antagonists & inhibitors* / Q000096:biosynthesis*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000096:biosynthesis; D052247:Nitric Oxide Synthase Type II; D013329:Structure-Activity Relationship
chemical_list: D005419:Flavonoids; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse