Elderflower (Sambucus nigra L) hydrophilic extracts possess antioxidant and cell viability protective effects against oxidative stress

Abstract

Elderflowers have been used as a first-line treatment for colds and flu since ancient times because they have antiviral, antibacterial, anti-inflammatory effects. There are data demonstrating that aqueous elderflower extracts have antioxidant activity. However, the analyses were mostly performed using only chemical methods, for example, DPPH, ABTS, and other assays. Therefore, it seems relevant to produce hydrophilic extracts from elderflowers using water (WES) and a mixture of water + 20% polyethylene glycol (Pg-WES), to compare their chemical composition, and to evaluate the antioxidant activity in cells under normal conditions, and to analyze their effect on cell viability under oxidative stress conditions. The elder flowers were obtained from a pharmacy (a manufacturer “Emili”). The extracts were prepared in an ultrasonic bath at room temperature for 20 minutes. The phenolic compounds were determined by the Folin-Ciocalteu method. The extracellular and intracellular ROS concentrations in C6 glial cells were assessed fluorometrically. The viability of cells was performed after staining of nuclei. Data analysis was performed by using SigmaPlot. The results showed that the total amount of phenolic compounds (PC) detected in WES was about 4-fold less than in ethanolic extracts, but about 10 times higher if compared to the results of other scientists who produced the tea infusions. The addition of PEG solvent to water increased the total phenolic content by more than twice. Both extracts reduced the level of extracellular and intracellular ROS in a concentration-dependent manner. Notably, the Pg-WES was found to be effective at much lower concentrations. Under high oxidative stress, when exposure to 100 µM H2O2 for 24 h resulted in the death of all cells, the Pg-WES had the high protective effect, since it reduced the population of dying cells by half when applied at 40 µg/mL PC, whereas the WES at the same concentration was half as effective. At milder oxidative stress conditions (75 µM H2O2 for 6 h and only 9% of cell death), both hydrophilic extracts (starting at 20 µg/mL) restored the cell viability to the control levels.