Chemical composition, antiradical, anti-collagenase, and anti-inflammatory activities of Prunus padus L. flower extract

Based on the ethnobotanical knowledge found in the records of Latvian folk medicine from the 19th century and due to the lack of studies related to the pharmacological activities of P. padus flowers, the aim of the study was to assess the chemical composition, antiradical, anti-collagenase, and anti-inflammatory activities of the ethanolic extract of P. padus flowers (PPFE). Flower extracts of P. padus were subjected to phytochemical analysis using gas chromatography-mass spectrometry and liquid chromatography-mass spectrometry techniques to determine the chemical composition. Antiradical activity of PPFE was measured as its ability to scavenge the 2,2-diphenyl-1-picryl hydrazyl (DPPH) free radical and the total phenolic content was tested by the Folin-Ciocalteu method. Anti-collagenase activity was investigated using a spectrophotometric method in vitro. The effect of PPFE on inflammation was evaluated by measuring specific markers using flow cytometry and assessing pro-inflammatory cytokine (IL-6) release by bone marrow-derived macrophages (BMDMs) ex vivo. The three major compounds of the ethanolic extract of P. padus flowers were quercetin diglycosides, chlorogenic acid, and di-caffeoyl-coumaroyl spermidine, which was tentatively identified for the first time in P. padus flowers. Total phenolic content of PPFE was 85.19 mg GAE/g extract and the EC50 value in the DPPH assay was 0.55 mg/ml. PPFE inhibited collagenase activity in a dose-dependent manner. Preincubation of BMDMs with PPFE reduced the population of M1 (pro-inflammatory) and increased the population of M2 (anti-inflammatory) macrophages after 24 h treatment. Moreover, PPFE decreased pro-inflammatory cytokine IL-6 release from BMDMs for 35% and 25% at concentrations of 500 and 250 µg/ml, respectively. PPFE is rich in bioactive components, mainly phenolic compounds. PPFE showed a significant anti-inflammatory effect, supporting its ethnomedicinal use reported in the records of Latvian folk medicine for the reduction of inflammatory processes.