Protective antioxidative effects of caffeic acid phenethyl ester (CAPE) in the thyroid and the liver are similar to those caused by melatonin

BACKGROUND Whereas oxidative reactions occur in all tissues and organs, the thyroid constitutes such an organ, in which oxidative processes are indispensable for physiological functions. In turn, numerous metabolic reactions occurring in the liver create favourable conditions for huge oxidative stress. Melatonin is a well-known antioxidant with protective effects against oxidative damage perfectly documented in many tissues, the thyroid and the liver included. Caffeic acid phenethyl ester (CAPE), a component of honeybee propolis, has been suggested to be also an effective antioxidant. The aim of the study was to evaluate the effects of CAPE on Fenton reaction-induced oxidative damage to membrane lipids (lipid peroxidation, LPO) in porcine thyroid and liver, and to compare the results with protective effects of melatonin. METHODS Thyroid and liver homogenates were incubated in the presence of CAPE (500; 100; 50; 10; 5.0; 1.0 μM) or melatonin (500; 100; 50; 10; 5.0; 1.0 μM), without or with addition of FeSO4 (30 μM) + H2O2 (0.5 mM). The level of lipid peroxidation was measured spectrophotometrically and expressed as the amount of MDA + 4-HDA (nmol) per mg of protein. RESULTS Whereas CAPE decreased the basal LPO in a concentration-dependent manner in both tissues, melatonin did not change the basal LPO level. When antioxidants were used together with Fenton reaction substrates, they prevented - in a concentration-dependent manner and to a similar extent - experimentally-induced LPO in both tissues. CONCLUSIONS Protective antioxidative effects of CAPE in the thyroid and the liver are similar to those caused by melatonin. CAPE constitutes a promising agent in terms of its application in experimental and, possibly, clinical studies.