Antioxidative activity of commercial liquorice samples and their phytochemical constituents in vitro on cellular level

In previous studies we found a remarkable antioxidative activity of liquorice extracts in cell-based in vitro assays. When piglet intestinal epithelial cells (IPEC-J2) were pre-incubated with liquorice extracts and challenged by hydrogen peroxide, formation of ROS as measured by a fluorescein probe (DCFH-DA) was inhibited. Moreover, glycyrrhizin was not responsible for the observed activity. In order to identify the active principle, 10 commercial extracts of Glycyrrhiza glabra and one plant powder were compared analytically (LC-QTOF-MS) and tested for antioxidative effects in the same cell-based assay. Correlations between bioactivity and the amounts of phytochemicals and phytochemical classes were calculated. The more abundant phytochemicals were tested as pure compounds in the cell-based assay at 0.1 – 10.0 µg/mL. The liquorice samples reduced the oxidative stress signals by 31 – 83% when tested at 30 – 60 µg/mL. Of all tested phytochemicals, only glabridin significantly reduced the oxidative stress signal in cells by 33% at 10 µg/mL (p < 0.05). Also, glabridin abundance in liquorice samples was correlated with bioactivity (r = 0.58). Antioxidative effects of commercial liquorice samples seemed to be related to their flavonoids. Additive or synergistic effects are very likely, since none of the tested single phytochemicals showed an activity sufficiently high to explain the activity of extracts. Glabridin had the strongest antioxidative activity among the tested substances and might contribute most to the observed activity of the liquorice samples. The authors declare no confilct of interest.

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Artikel online veröffentlicht:
12. Dezember 2022