Effects Of Vasorelaxation And Protection From Red Blood Cell Oxidant Damage Of Propolis' Extracts

Propolis is a natural substance collected by honeybees from buds and exudates of certain plants; it had been widely used in folk medicines in many regions of the world. We investigated the vasorelaxant and antioxidant ability of extracts of propolis from Gansu, China, including water extract of propolis (WEP) and ethanol extract of propolis (EEP).We investigated the vasorelaxant of extracts of propolis. Guinea pig thoracic aortic rings were used in experiments. The results showed that WEP had no effect, and EEP had concentration-dependent relaxant effects to KC1 and phenylephrine (PE) induced contractions, and these effects were endothelium-depended. In vessel rings pretreated with N-nitro-L-arginine (L-NNA), methylene blue (MB), or indomethacin the responses to EEP were attenuated. This indicated the relaxant effects of EEP could involve the release of nitric oxide and prostaglandins from the endothelium. In addition, the relaxant action of the EEP included inhibition of Ca²⁺ influx and release of Ca²⁺ from intracellular stores.We also studied the inhibitory effects of propolis extract on a water-soluble azo compound 2,2'-azobis(2-amidinopropane hydrochloride) (AAPH)- induced oxidative damage in human red blood cells. At 37℃AAPH could induce hemolysis and lipid peroxidation, the extracts of propolis had concentration-depended inhibitory effect to both of them, and the effect of EEP was stronger than WEP. In addition, by SDS-polyacrylamide gel electrophoresis and comet assay, we also proved that WEP or EEP had protection effects to DNA and protein damage, and EEP was more potent than WEP.