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 twodimensional NMR for the first time. In addition, these polyphenol monomers manifested desirable DPPH center dot scavenging capacity (EC50: 39.55 +/- 1.43-612 +/- 8.45 mu M) and ABTS+center dot scavenging capacity (EC50: 32.12 +/- 0.58-512 +/- 25.12 mu M), 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.

Automated summary

This study isolated, purified, and identified phenols from celery leaves and evaluated their antioxidant activities. A total of seven polyphenol monomers were identified, and chrysoeriol 7-O-glucoside was identified for the first time. The polyphenol monomers exhibited significant DPPH· and ABTS+· scavenging capacities. The position and quantity of hydroxyl groups on the B-ring and the methylation degree of 3-OH played a crucial role in regulating antioxidant activities.