LC/MS/MS Phenolic Profile, Antioxidant Capacity, Angiotensin-Converting Enzyme (ACE) and Glutathione S Transferase (GST) Inhibitory Properties of Ultrasound-Assisted Propolis Extracts

Resinous beehive product propolis has many biological activities. It contains various aromatic substances that have great differences in their chemical composition depending on the natural flora. Thus, chemical characterization and biological properties of propolis samples is an important subject for the pharmaceutical industry. In this study, the propolis samples collected from three cities in Turkey were prepared as methanol (MEP), ethanol (EEP), chloroform (ChlEP), hexane (HxEP), and ethyl acetate (EAEP) extracts using an ultrasonic assisted technique. The antioxidant capacities of the samples were evaluated by free radical scavenging activity (DPPH), cation radical scavenging activity (ABTS), and reducing activity (CUPRAC) and (FRAP). The strongest biological activities were detected in ethanol and methanol extracts. Enzyme inhibition of the propolis samples were determined against the human glutathione S-transferase (GST) and angiotensin converting enzyme (ACE). IC50 values of MEP1, MEP2, and MEP3 samples against the ACE were found as 13.9 mu g/mL, 14.8 mu g/mL, and 12.8 mu g/mL, while against the GST IC50 values of MEP1, MEP2, and MEP3 samples were as 5.92 mu g/mL, 9.49 mu g/mL, and 5.72 mu g/mL. To know the possible causes of the biological test results advanced LC/MS/MS method was applied. trans-ferulic acid, kaempferol, and chrysin were found as the most abundant phenolic compounds in each sample. The propolis extracts obtained using the proper solvent have a good potential to be used in pharmaceuticals to treat the diseases related to oxidative damage, hypertension, and inflammation. Finally, the interactions between chrysin, trans-ferulic acid and kaempferol molecules with ACE and GST receptors were analyzed using molecular docking study. Selected molecules interact with active residues by binding to the active site of the receptors.