title: Antioxidants from Rabdosia japonica.
abstract: The antioxidant activities of phenolic compounds: pedalitin, quercetin, rutin, isoquercitrin, and rosmarinic acid, isolated from the dried leaves of Rabdosia japonica Hara (Labiatae) were elucidated. All the phenolics tested exhibited superoxide scavenging activity and an inhibitory effect on xanthine oxidase (EC 1.1.3.22), and pedalitin showed the most potent antioxidant activity. Pedalitin prevents the generation of superoxide radicals in part by inhibiting xanthine oxidase competitively. Both pedalitin and quercetin inhibited uric acid formation by xanthine oxidase, and the inhibition kinetics analysed by Lineweaver-Burk plots found both flavonoids to be competitive inhibitors. On the other hand, isoquercitrin, rutin and rosmarinic acid were effective in scavenging superoxide radicals generated by the xanthine-xanthine oxidase system without inhibiting the enzyme.
authors.affiliation: Department of Biochemistry, Okayama University Graduate School of Medicine and Dentistry, Okayama 700-8558, Japan.
authors.forename: Noriyoshi
authors.initials: N
authors.lastname: Masuoka
authors.forename: Takahiko
authors.initials: T
authors.lastname: Isobe
authors.forename: Isao
authors.initials: I
authors.lastname: Kubo
mesh_terms: D000975:Antioxidants / Q000737:chemistry* / Q000302:isolation & purification / Q000494:pharmacology; D001713:Biphenyl Compounds; D002934:Cinnamates / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology; D053630:Depsides; D047309:Flavones / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology; D005419:Flavonoids / Q000378:metabolism; D044948:Flavonols / Q000737:chemistry* / Q000302:isolation & purification / Q000494:pharmacology; D020128:Inhibitory Concentration 50; D037602:Isodon / Q000737:chemistry*; D010851:Picrates / Q000378:metabolism; D010936:Plant Extracts / Q000737:chemistry* / Q000302:isolation & purification / Q000494:pharmacology; D018515:Plant Leaves / Q000737:chemistry; D013481:Superoxides / Q000138:chemical synthesis; D014527:Uric Acid / Q000378:metabolism; D014969:Xanthine Oxidase / Q000037:antagonists & inhibitors / Q000378:metabolism; D000097123:Rosmarinic Acid
chemical_list: D000975:Antioxidants; D001713:Biphenyl Compounds; D002934:Cinnamates; D053630:Depsides; D047309:Flavones; D005419:Flavonoids; D044948:Flavonols; D010851:Picrates; D010936:Plant Extracts; D013481:Superoxides; D014527:Uric Acid; D014969:Xanthine Oxidase; D000097123:Rosmarinic Acid; C510777:pedalitin; C004931:1,1-diphenyl-2-picrylhydrazyl; C017875:fisetin