Phytochemistry of Lotus corniculatus flowers: a new and efficient method for determination of bioactive compounds by LC–ESI–MS/MS and a novel potentiometric PVC membrane sensor for the evaluation of antioxidant activity

Natural products play an essential role in food and pharmaceuticals. Quantification of bioactive compounds in plants is essential for the drug development process. Moreover, the presentation of the antioxidant effects of plants gains great interest for their therapeutic effect. A new and efficient technique was advanced for the determination of bioactive compounds in the methanol extract of Lotus corniculatus flowers (MLCF) by Liquid chromatography electrospray ionization tandem mass spectrometry (LC–ESI–MS/MS). A potentiometric polyvinyl chloride (PVC) membrane sensor was progressed for the evaluation of 2,2-Diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity and total phenolic content of MLCF. Isoquercitrin (200.8 µg/g extract), quercetin-3-D-xyloside (189.1), kaempferol-3-glucoside (35.9), coumarin (16.3), salicylic acid (5.3), quercetin (2.51), fisetin (0.81) were detected as major products among the 39 standards. DPPH free radical scavenging effect and total phenolic content of MLCF were determined by potentiometric PVC membrane sensor, and MLCF inhibited the DPPH^• with a value of 71.4%. In addition, the total phenolic content was determined to be 228.6 ± 0.05 mg gallic acid eq/g extract. Lotus corniculatus leaves could be a significant source of isoquercitrin, and this plant can be accepted as a good antioxidant agent.