Antioxidant effects of quinoline alkaloids and 2,4-di-tert-butylphenol isolated from Scolopendra subspinipes.

The oxidized low-density lipoprotein (ox-LDL) plays a critical role at the early stages of atherosclerosis. Thus, the prevention of LDL-oxidation by antioxidants may arrest the progression of atherosclerosis. Two quinoline alkaloids, 3,8-dihydroxyquinoline (1) and 2,8-dihydroxy-3,4-dimethoxyquinoline (3), and 2,4-di-tert-butylphenol (2) were isolated from the dried body of Scolopendra subspinipes. Compounds 1-3 exhibited antioxidant activities on copper-mediated (1: IC50=2.6 microM, 2: IC50=8.2 microM, 3: IC50=63.0 microM), AAPH-mediated oxidation (1: IC50=3.9 microM, 2: IC50=9.9 microM, 3: IC50=71.8 microM), and SIN-1-mediated oxidation (1: 70%, 2: 52%, 3: 29% at 5.0 microM) in the TBARS assay. The antioxidant activities of compounds 1-3 were tested with respect to other parameters, such as the lag time of conjugated diene fromation, relative electrophoretic mobility (REM) of ox-LDL, and apoB-100 fragmentation on copper-mediated LDL-oxidation. In addition, compounds 1-3 showed 1,1-diphenyl-2-picrylhydrasyl (DPPH) radical scavenging activity and compound 1 also exhibited metal chelating activity.