Inhibitors of 15-Lipoxygenase from Orange Peel

Abstract

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.

Antioxidant activity of O-protected derivatives of (-)-epigallocatechin-3-gallate: inhibition of soybean and rabbit 15-lipoxygenases

“…Scavenging activity towards the diphenylpicrylhydrazyl (DPPH) radical was measured as the decrease in absorbance at 517 nm of a methanolic DPPH solution (A 517 = 1.0, 2.95 ml) over a 5-min period after addition of 50 µL of a DMSO solution of test substance. 45 Appropriate corrections were made for dilution and for absorbance of the reaction product, reduced DPPH. Calculation of radical scavenging activity was carried out as previously described.…”

Evaluation of Anti-inflammatory and Antisickling Potentials of Archidium ohioense (Schimp. ex Mull) Extracts

“…Anti-lipoxygenase activity of the extracts with linoloeic acid as substrate was measured as described by Malterud and Rydland (2000) [16]. The assay mixture consisted of 150 µl phosphate borate (1/15 M, pH 7.5), extract solution (50 µl), 50 µl enzyme solution (0.28 U/ml in phosphate borate).…”

Structure-based design, synthesis, molecular docking study and biological evaluation of 1,2,4-triazine derivatives acting as COX/15-LOX inhibitors with anti-oxidant activities

“…The assay was performed according to the previously reported method 37 . The compounds were dissolved in DMSO and phosphate buffer.…”