Portuguese propolis enriched phenolic extract: reactive oxygen scavenging and cytoprotective activities

Propolis, a resinous natural product produced by honeybees, is claimed to have a wide range of beneficial activities for human health which have been attributed to its phenolics. In general, phenolics account for approximately half of propolis weight, although its content and composition can greatly vary with propolis geographical origin. This study aims determining the antioxidant and cytoprotective properties of Northeast Portuguese propolis. The propolis hydroethanolic purified extract (PPE) was obtained by extraction at 70 °C/1 h and recovery onto SPE C18 cartridges. Total phenolic content and identification of the main phenolics in the PPE were assessed by the Folin Ciocalteu method and by HPLC-DAD analysis, respectively. The reactive oxygen species (ROS) scavenging and cytoprotective properties of PPE were evaluated in dichromate potassium-stimulated (DK) HepG2 cells model. ROS scavenging ability was measured by flow cytometry, after DK incubation for 48 h and cytoprotective activity was estimated by the MTT assay, after DK exposure for 6 h or 72 h. The total amount of phenolics in the PPE accounted for 375.4±5.8 mg GAE/g of extract and this was enriched in chrysin, pinocembrin and pinobanksin-3-O-acetate. Bioactivity assays showed that the PPE decreased the rate of ROS production about 50% and exerted an effective protection Overall the results emphasize important activities of PPE that can be related to the high content of phenolic compounds