Rapid screening for novel antioxidants in Glycyrrhiza inflata using high-resolution peak fractionation

• A high-purity peak fraction library of Glycyrrhiza inflata was developed.
• Ten compounds isolated from G. inflata were screened as potential antioxidants.
• Eight flavonoids could induce the expression of Nrf2-related genes.
• Five novel Nrf2 activators were identified in this study.
• Licochalcone B showed stronger Nrf2 activity and lower cytotoxicity than TBHQ.

Licorice is often consumed as a flavoring agent in food products, and a commonly used herb with several bioactivities, including antioxidation. The bioactive components in licorice against oxidative stress have not been fully elucidated. Nuclear-factor-E2 related factor 2/antioxidant responsible element (Nrf2/ARE) is a major pathway protecting cells from oxidative damage. In this study, an ARE-luciferase/β-galactosidase enzyme dual reporter gene assay was used in conjunction with high-resolution peak fractionation to rapidly identify antioxidants in Glycyrrhiza inflata. The structures of potential antioxidants were identified by high-performance liquid chromatography (HPLC) coupled with quadrupole time-of-flight tandem mass spectrometry (Q-TOF MS/MS). Ultimately, eight active antioxidants were identified and confirmed by real-time polymerase chain reaction (RT-PCR). Five novel Nrf2 activators are reported. This study presents potential Nrf2 activating compounds in licorice and provides further evidence for the antioxidant properties of G. inflata, which is important for elucidating the ingredients partially responsible for the antioxidant properties of licorice.