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 μM, 2: IC50=8.2 μM, 3: IC50=63.0 μM), AAPH-mediated oxidation (1: IC50=3.9 μM, 2: IC50=9.9 μM, 3: IC50=71.8 μM), and SIN-1-mediated oxidation (1: 70%, 2: 52%, 3: 29% at 5.0 μM) 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.