Inhibitors of 15-lipoxygenase from orange peel.
A series of polymethoxylated flavonoids has been isolated from orange peel, and their inhibitory activity toward soybean 15-lipoxygenase was determined. The strongest inhibition was shown by 3,5,6,7,3',4'-hexamethoxyflavone (IC(50) = 49 +/- 5 microM). Sinensetin, nobiletin, tangeretin, tetramethylscutellarein, and 3,5, 6,7,8,3',4'-heptamethoxyflavone were somewhat less active, with IC(50) values of 70-86 microM, comparable to the positive control quercetin (IC(50) = 68 +/- 5 microM). Demethylation apparently results in less active compounds, with 5-O-demethylsinensetin having an IC(50) value of 144 +/- 10 microM. Some other orange peel constituents were isolated and tested as well, hesperidin (IC(50) = 180 +/- 10 microM) and ferulic acid (111 +/- 2 microM), showing moderate activity. The polymethoxylated flavonoids were virtually inactive as scavengers of the diphenylpicrylhydrazyl radical. Hesperidin was only slightly active (24.2 +/- 0.7% scavenged at a concentration of 2 mM), and ferulic acid showed good activity (IC(50) = 86.4 +/- 0.7 microM). From this, it appears that orange peel constituents may counteract enzymatic lipid peroxidation processes catalyzed by 15-lipoxygenase in vitro. The radical scavenging activity of orange peel extracts is only modest.
Malterud
K E
KE
Department of Pharmacognosy, School of Pharmacy, The University of Oslo, P.O. Box 1068 Blindern, N-0316 Oslo, Norway. k.e.malterud@farmasi.uio.no
Rydland
K M
KM
D001093:Arachidonate 15-Lipoxygenase / Q000378:metabolism*; D002957:Citrus / Q000737:chemistry*; D005419:Flavonoids / Q000737:chemistry / Q000302:isolation & purification* / Q000494:pharmacology; D016166:Free Radical Scavengers / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology; D016859:Lipoxygenase Inhibitors / Q000302:isolation & purification* / Q000494:pharmacology; D011794:Quercetin / Q000494:pharmacology; D013329:Structure-Activity Relationship
D005419:Flavonoids; D016166:Free Radical Scavengers; D016859:Lipoxygenase Inhibitors; D011794:Quercetin; D001093:Arachidonate 15-Lipoxygenase