Quantitative analysis of phenolics in Trifolium pratense L. flowers and evaluation of antioxidant activity by sensory

Trifolium pratense L. flowers (TPF) were collected and dried in shade in this study. After extraction in methanol, a diluted solution was applied to the liquid chromatography electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS) device to determine the bioactive compounds quantitatively. Isoquercitrin (38.64 mg/g extract), coumarin (13.66 mg/g extract), and catechin (12.52 mg/g extract) were verified as major products. Antioxidant activity of TPF was performed using a potentiometric PVC membrane sensor to evaluate 2,2-Diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity and total phenolic content of TPF. TPF inhibited the DPPH radical as 31.4 ± 0.02% at the 500-ppm concentration. However, the DPPH activity of gallic acid was determined as 81.43 ± 0.07% and 92.44 ± 0.1% at the TPF concentrations of 12.5 ppm and 25 ppm, respectively. In addition, the total phenolic content was calculated to be 82.4 ± 0.15 mg gallic acid eq/g extract. It was observed that TPF has the potential to be an antioxidant and a valuable source of isoquercitrin, coumarin, and catechin.