A phytochemical content analysis, and antioxidant activity evaluation using a novel method on Melilotus officinalis flower

Abstract

Conducting content analysis is very important to elucidate and expand the different usage areas of plant components. Today's content analysis methods provide very reliable results. However, the high cost of these methods and the need for trained personnel bring other challenges. Therefore, simple, fast, and low-cost content analysis methods are a great need. In this study, the phenolic content of Melilotus officinalis flower extracts was investigated using LC-MS/MS analysis, and its antioxidant activity was determined with a novel method employing a PVC membrane sensor. In the method, for the first time, the antioxidant activities of M. officinalis flowers were determined in an economical, sensitive, fast, and stable manner using a PVC potentiometric sensor. Sensor measurements were performed using DPPH and FCR molecules, resulting in 25.71 mg.g^-1 activity values and 117.524 mg.g^-1, respectively. LC-MS/MS analysis was conducted to investigate the presence of 45 standard phenolic compounds in M. officinalis. The results revealed that coumarin and isoquercitrin were the major phenolic compounds in the M. officinalis flower extract. The findings of LC-MS/MS analyses of the extracts show moderate phenolic content presence in the M. officinalis flower extracts. The total phenolic content determined by LC-MS/MS analysis was consistent with the PVC membrane sensor analysis results. The studies of molecular docking aimed to identify the most effective active sites, and the Moldock scores (-57.13, -105.93) and binding energies (4.5 kcal.mol^-1, -7.9 kcal.mol^-1) of coumarin and isoquercitrin molecules. The results of molecular docking studies suggest that isoquercitrin exhibits a stronger inhibitory effect on DD-peptidase enzymes compared to coumarin.