title: Flavonoids from the leaves of Litsea japonica and their anti-complement activity.
abstract: Four flavonoids, epicatechin (1), afzelin (2), quercitrin (3), and tiliroside (4), were isolated from the leaves of Litsea japonica (Thunb.) Jussieu (Lauraceae). The structures of compounds were identified by comparing their chemical and spectral data with those previously reported. The flavonoids (1-4) were tested for their anti-complement activity against classical pathway of complement system. Compounds 2-4 showed inhibitory activity against complement system with IC50 values of 258, 440, and 101 microm, respectively, whereas 1 was inactive. For the evaluation of the structure-activity relationship of 5,7-dihydroxyflavones, myricitrin (5) from Juglans mandshurica also tested for it's anti-complement activity and is inactive in this assay system. Furthermore, compounds 2, 3, and 5 were hydrolyzed with naringinase to give kaempferol (2a), quercetin (3a), and myricetin (5a), and these were also tested for their activity. Of the three aglycones, 2a exhibited anti-complement activity with an IC50 value of 730 microM, while 3a and 5a were inactive. The inhibitory potencies of 2, 2a, 3, 3a, 5, and 5a against complement activity increased in inverse proportion to number of free hydroxyls on B-ring of 5,7-dihydroxyflavone. Of the compounds tested, 4 showed the most potent inhibitory activity against the complement system.
authors.affiliation: Laboratory of Immunomodulator, Korea Research Institute of Bioscience and Biotechnology, Daejeon Korea.
authors.forename: Sun-Young
authors.initials: SY
authors.lastname: Lee
authors.forename: Byung-Sun
authors.initials: BS
authors.lastname: Min
authors.forename: Jung-Hee
authors.initials: JH
authors.lastname: Kim
authors.forename: Joongku
authors.initials: J
authors.lastname: Lee
authors.forename: Tae-Jin
authors.initials: TJ
authors.lastname: Kim
authors.forename: Chan-Soo
authors.initials: CS
authors.lastname: Kim
authors.forename: Young-Ho
authors.initials: YH
authors.lastname: Kim
authors.forename: Hyeong-Kyu
authors.initials: HK
authors.lastname: Lee
mesh_terms: D003169:Complement Inactivator Proteins / Q000737:chemistry / Q000494:pharmacology*; D003165:Complement System Proteins / Q000187:drug effects*; D005419:Flavonoids / Q000737:chemistry / Q000494:pharmacology; D006801:Humans; D020128:Inhibitory Concentration 50; D032862:Litsea; D008517:Phytotherapy; D010936:Plant Extracts / Q000737:chemistry / Q000494:pharmacology*; D018515:Plant Leaves; D013329:Structure-Activity Relationship
chemical_list: D003169:Complement Inactivator Proteins; D005419:Flavonoids; D010936:Plant Extracts; D003165:Complement System Proteins