Effects of processing methods and extraction solvents on the chemical content and bioactive properties of propolis

The aim of this study was to evaluate the bioactive properties of propolis extract prepared using different solvents and different extraction methods. The extracts were analyzed by gas chromatography–mass spectrometry (GC–MS) and the differences between their antibacterial activities were evaluated by disc diffusion method. At the same time, bioactive properties of different concentrations of propolis extracts were investigated on human umbilical vein endothelial cells (HUVEC). The proliferative effects and cytotoxic effects of the extracts were determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and lactate dehydrogenase (LDH) analyzes, respectively. Total antioxidant capacity (TAC) and total oxidative status (TOS) parameters were used in assessing biochemical effects in the HUVEC cell line. The DNA damage was also analyzed by 8-oxo-2-deoxyguanosine (8-OHdG) level as indicators of genotoxicity. As a result of the MTT analysis conducted within the scope of the present study, the extracts tested were sorted as 95% ethanol extract of propolis (PEE95) > ultrasonic ethanol extract of propolis (PUEE) > 50% ethanol extract of propolis (PEE50) > ultrasonic water extract of propolis (PUWE) in terms of the effectiveness of their cell viabilities. It was observed that high concentrations of PEE95 induced LDH release. In addition to this, our findings have shown that PEE50, PUEE and PUWE increased oxidative stress at high concentrations. According to 8-OH-dG analysis, all tested extracts were found to be non-genotoxic. The results obtained from antibacterial activity and minimum inhibition concentration tests showed that PUEE and PEE95 had stronger antibacterial effects than PEE50 and PUWE. All these results indicated that propolis has beneficial effects for human health and therefore it is a valuable product which can be used as a food supplement.