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. 2024 Jun 28;17(7):852.
doi: 10.3390/ph17070852.

Neuroprotective Effects of Glycyrrhiza glabra Total Extract and Isolated Compounds

Affiliations

Neuroprotective Effects of Glycyrrhiza glabra Total Extract and Isolated Compounds

Ali O E Eltahir et al. Pharmaceuticals (Basel). .

Abstract

Glycyrrhiza glabra L. is a plant commonly utilized in herbal medicine and stands out as one of the more extensively researched medicinal plants globally. It has been documented with respect to several pharmacological activities, notably, neuroprotective effects, among others. However, the neuroprotective activity of pure phenolic compounds has not been reported yet. The chromatographic of a methanolic extract yielded twenty-two compounds, viz.: naringenin 4'-O-glucoside (1), 3',4',7-trihydroxyflavanone (butin) (2), liquiritin (3), liquiritin apioside (4), abyssinone (5), glabrol (6), isoliquiritin (7), neoisoliquiritin (8), isoliquiritin apioside (9), licuraside (10). 3'[O], 4'-(2,2-dimethylpyrano)-3,7-dihydroxyflavanone (11), glabrocoumarin (12), glabrene (13), isomedicarpin (14), 7-hydroxy-4'-methoxyflavone (formononetin) (15), ononin (16), glycyroside (17), (3S)-7,4'-dihydroxy-2'-methoxyisoflavan (18), glabridin (19), neoliquiritin (20), 3,11-dioxooleana-1,12-dien-29-oic acid (21), and 3-oxo-18β-glycyrrhetinic acid (22). The results of the neuroprotection evaluation showed that G. glabra total extract (TE) and compounds 1, 7, 11, 16, and 20 protected SH-SY5Y cells by inhibiting the depletion of ATP and elevated caspase 3/7 activities induced by MPP+. Indeed, this study reports for the first time the structure and activity of compound 11 and the neuroprotective activity of some phenolic constituents from G. glabra.

Keywords: Glycyrrhiza glabra; licorice; neuroprotection; phenolic compounds.

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Conflict of interest statement

The authors declare no conflicts of interest.

Figures

Figure 1
Figure 1
Chemical structures of the compounds isolated from G. glabra.
Figure 2
Figure 2
Chemical structure and important HMBC correlations of 11, and the structure of 3,4′,7-trihydroxy-3′-prenylflavanone.
Figure 3
Figure 3
Dose–response of licorice TE and compounds. MTT cytotoxicity assay on SH-SY5Y cells treated with increasing concentrations (12.5, 25, and 50 µg/mL) of licorice TE and compounds (2.5, 5, and 10 µg/mL) for 24 h. After assays, cell viability was expressed as a percentage of control, and each bar represents the mean + SEM of at least three replicate experiments obtained from quadruple wells. Treated cells were compared to control cells; significance levels are indicated. The significance of the difference when control cells were compared to treated cells is indicated by * p< 0.05, ** p < 0.01, *** p < 0.001, and **** p < 0.0001.
Figure 3
Figure 3
Dose–response of licorice TE and compounds. MTT cytotoxicity assay on SH-SY5Y cells treated with increasing concentrations (12.5, 25, and 50 µg/mL) of licorice TE and compounds (2.5, 5, and 10 µg/mL) for 24 h. After assays, cell viability was expressed as a percentage of control, and each bar represents the mean + SEM of at least three replicate experiments obtained from quadruple wells. Treated cells were compared to control cells; significance levels are indicated. The significance of the difference when control cells were compared to treated cells is indicated by * p< 0.05, ** p < 0.01, *** p < 0.001, and **** p < 0.0001.
Figure 4
Figure 4
Licorice TE and compounds show protection in SH-SY5Y cells. Cells were pre-treated with TE (A) and compounds (BF) before exposure to MPP+ for 24 h. Each bar represents mean percentage cell viability relative to control, and significance of difference is indicated with * p < 0.05, ** p < 0.01, *** p < 0.001, and **** p < 0.0001 when TE/compounds are compared to MPP+, and Φ when MPP+ -treated cells are compared to control.
Figure 5
Figure 5
Effect of licorice TE and compounds on MPP+-induced depletion of ATP. Cells were pre-treated with 50 µg/mL of licorice TE and 2.5 µg/mL of compounds before exposure to 2000 µM of MPP+ for 24 h, and ATP levels were assessed. Each bar represents the mean percentage of ATP production relative to control, and the significance of the difference is indicated as * p < 0.05 and ** p < 0.01 when extract/compounds are compared to MPP+ and when MPP+-treated cells are compared to control.
Figure 6
Figure 6
Licorice TE and compounds attenuate MPP+-induced increase in caspase 3/7 activities. Cells were pre-treated with 50 µg/mL of licorice TE and 2.5 µg/mL of compounds before exposure to 2000 µM of MPP+ for 24 h, and caspase 3/7 activities were determined. Each bar represents the level of caspase 3/7 expressed as a multiple of the control, and significance of difference is indicated by ** p < 0.01 and *** p < 0.001 when TE/compounds were compared to MPP+, and Φ when MPP+-treated cells were compared to control.

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