Lipid peroxidations (LPOs) by reactive oxygen species induce injury to lipids of the membrane or the formation of lipofuscin (1). It was demonstrated that LPOs participate in arteriosclerosis (2), diabetes meffitus (3), halothane hepatotoxicity (4), and liver disease (5). The mechanism of action involves interaction of haemoglobin, ferrous salt, and hydrogen peroxide derived the generation of hydroxyl radicals as a reactive oxygen species. Some aromatic herbs (e.g. Aurantii pericarpium, Caryophylli fibs, Cinnamomi cortex, and Foeniculi fructus) have inhibitory effects on the peroxidation of llnoleic acid induced by the interaction of haemoglobin and hydrogen peroxide (6). The effects of Caryophylii fibs are appreciably greater than that of dl-a-tocopherol. In this paper, we investigated whether eugenol, a main component of Caryophylii fibs, has inhibitory effects on the peroxidation of lecithin induced by reactive oxygen derived from the interaction of ferrous salt and hydrogen peroxide (Fe2-H2O2 system). It was found that eugenol and related compounds, as shown in Table 1, have such effects.Anethol, dl-benzylisoeugenol, eugenol, dlisoeugenol, dl-isosafroeugenol, dl-methylisoeugenol and methyleugenol were obtained from Eichodo Chemicals Co. (Osaka, Japan). Their grades were confirmed to be 90 -95 % purity by HPLC. Ferrous ammonium sulfate, hydrogen peroxide, lecithin (from egg yolk), thiobarbituric acid (TBA), dl-a-tocopherol, and catalase (EC 11.1.6, from bovine liver) were purchased from Wako Pure Chemicals Co. (Osaka, Japan). The major fatty acids of lecithin are confirmed to be linoleic acid (45.1%), palmitic acid (22.6%), and stearic acid (20.4%) by the method of Stoffel et al. (8).The sample, dl-a-tocopherol as antioxidant or catalase as a hydrogen peroxide-scavenger was added to the reaction mixture containing 10mg/mi of lecithin, 10mM hydrogen peroxide, and 10mM ferrous ammonium sulfate in 50mM tris-HC1 buffer (pH 7.4) in a total volume of 2 ml. This mixture was incubated at 37 °C for 1 h. 2 ml of 10% trichloroacetic acid were added to the incubated reaction mixture. 2.4 ml of 0.67% TBA solution were added to 2 ml of the sup ernatant after centrifugation of this soluPlanta Med. 60(1994)282 © Georg Thieme verlag Stuttgart New York tion at 3000 r.p.m. for 10 mm. The peroxide of lecithin was determined by the TBA method (7). The inhibitory ratio of the sample was estimated by the following equation: absorbance absorbance Inhibitory ratio = without sample -with sample < 100 absorbance without sampleAll experimental data were expressed as the mean SE. of four experiments. Student's t-test was used for statistical analysis.As the absorbance without sample is 1.082 0.003, the concentration of this thiobarbituric acidreactive substance is determined to be 167.8 10.7 nmoll ml as maiondialdehyde. On addition of 10mM of the sample, the inhibitory ratios of the effective compounds are 93.3 0.9%foreugenol, 84.0 0.5%fordl-isoeugenol, and 77.1 6.9% for dl-isosafroeugenol. The inhibitory ratios of these compounds increas...
