Utilization of the Ability to Induce Activation of the Nuclear Factor (Erythroid‐derived 2)‐like Factor 2 (Nrf2) to Assess Potential Cancer Chemopreventive Activity of Liquorice Samples

Norazah Basar, Lutfun Nahar, Olayinka Ayotunde Oridupa, Kenneth J Ritchie, Anupam D Talukdar, Angela Stafford, Habibjon Kushiev, Asuman Kan, Satyajit D Sarker

Nuclear factor (erythroid-derived 2)-like factor 2 (Nrf2) is a transcription factor that regulates expression of many detoxification enzymes. Nrf2-antioxidant responsive element (Nrf2-ARE) signalling pathway can be a target for cancer chemoprevention. Glycyrrhiza glabra, common name, 'liquorice', is used as a sweetening and flavouring agent, and traditionally, to treat various ailments, and implicated to chemoprevention. However, its chemopreventive property has not yet been scientifically substantiated. To assess the ability of liquorice root samples to induce Nrf2 activation correlating to their potential chemopreventive property. The ability of nine methanolic extracts of liquorice root samples, collected from various geographical origins, to induce Nrf2 activation was determined by the luciferase reporter assay using the ARE-reporter cell line, AREc32. The antioxidant properties were determined by the 2,2-diphenyl-1-picryhydrazyl (DPPH) and the ferric-reducing antioxidant power (FRAP) assays. All extracts exhibited free-radical-scavenging property (RC50  = 136.39-635.66 µg/mL). The reducing capacity of ferrous ion was 214.46-465.59 μM Fe(II)/g. Nrf2 activation indicated that all extracts induced expression of ARE-driven luciferase activity with a maximum induction of 2.3 fold relative to control. These activities varied for samples from one geographical location to another. The present findings add to the existing knowledge of cancer chemoprevention by plant-derived extracts or purified phytochemicals, particularly the potential use of liquorice for this purpose. Copyright © 2016 John Wiley & Sons, Ltd.