Isolation and identification of polyphenol monomers from celery leaves and their structure-antioxidant activity relationship

This study aimed to isolate, purify and identify phenols from the celery leaves and further evaluate the antioxidant activities of the monomers in chemical system. Seven polyphenol monomers (a-g) were identified by HPLC-ESI-MS/MS after being separated by D101 macroporous resin, semi - preparative reversed-phase high-performance liquid chromatography (RP-HPLC) and sephadex LH-20. Interestingly, chrysoeriol 7-O-glucoside was identified from celery leaves by UV, IR, one dimensional nuclear magnetic resonance (NMR) and two-dimensional NMR for the first time. In addition, these polyphenol monomers manifested desirable DPPH• scavenging capacity (EC 50 : 39.55 ± 1.43–612 ± 8.45 μM) and ABTS+• scavenging capacity (EC 50 : 32.12 ± 0.58–512 ± 25.12 μM), respectively. Among them, the polyphenol monomers (a and b) with two hydroxyl groups (-OH) on the B ring in flavone skeleton had the strongest antioxidant activities. Moreover, the analysis of the structure-activity relationship showed that the position and quantity of -OH on the B-ring and the methylation degree of 3-OH played an important role in regulating antioxidant activities.