*2.4. Correlation between Plasma GA Content and Reduction of RBC Oxidative Parameters*

To assess if these licorice intake-related improvements and GA metabolites were correlated, we quantified the plasma GA content following the licorice intake (Figure 4). Plasma GA concentrations ranged from a minimum of 484 to1546 ng/mL in both groups, representative of great subjectivity in metabolizing licorice to yield GA. No significant

in Figure 4).

Methods.

fected by GA.

**3. Discussion**

difference was found between the mean GA plasma concentrations in the two groups (886.7 ± 329.3 ng/mL in CG vs. 1087.8 ± 261.6 ng/mL in PG; *p* = 0.0734). What is noteworthy is that we found a direct proportionality between the plasma GA content and a reduction in both diamide and DDS-NHOH-induced alterations (Figure 4), which resulted in highly significant for all parameters in CG, and less in PG (see correlation coefficients reported in Figure 4). difference was found between the mean GA plasma concentrations in the two groups (886.7 ± 329.3 ng/mL in CG *vs* 1087.8 ± 261.6 ng/mL in PG; *p* = 0.0734). What is noteworthy is that we found a direct proportionality between the plasma GA content and a reduction in both diamide and DDS-NHOH-induced alterations (Figure 4), which resulted in highly significant for all parameters in CG, and less in PG (see correlation coefficients reported

Plasma GA concentrations ranged from a minimum of 484 to1546 ng/mL in both groups, representative of great subjectivity in metabolizing licorice to yield GA. No significant

*Int. J. Mol. Sci.* **2021**, *22*, x FOR PEER REVIEW 7 of 13

**Figure 4.** Correlation between the plasma GA concentration and measured parameters, after 1 week of licorice treatment, in both CG (red points) and PG (blue points) groups. Upper graphs: stimulation with DDS-NHOH. Lower graphs: basal values (not stimulated). For each regression line, Pearson's correlation coefficient *r* is indicated, together with the corresponding *p*-value. To obtain the plasma GA concentration, an HPLC–MS full scan method was used as described in the **Figure 4.** Correlation between the plasma GA concentration and measured parameters, after 1-week of licorice treatment, in both CG (red points) and PG (blue points) groups. Upper graphs: stimulation with DDS-NHOH. Lower graphs: basal values (not stimulated). For each regression line, Pearson's correlation coefficient *r* is indicated, together with the corresponding *p*-value. To obtain the plasma GA concentration, an HPLC–MS full scan method was used as described in the Methods.

The highly significant proportionality between the plasmatic GA content and the reduction of diamide-induced alterations was consistent with previous in vitro observations [35], but only for the Tyr-P parameter. Compared to DDS-NHOH, GA was not so efficacious in reducing diamide-induced membrane glutathionylation and HMWA formation. On the contrary, the GA plasma concentration better fitted with the improvements of both membrane and cytosol parameters following DDS-NHOH treatment, thus evidencing those alterations induced by the two compounds were different and, so, differently af-The highly significant proportionality between the plasmatic GA content and the reduction of diamide-induced alterations was consistent with previous in vitro observations [35], but only for the Tyr-P parameter. Compared to DDS-NHOH, GA was not so efficacious in reducing diamide-induced membrane glutathionylation and HMWA formation. On the contrary, the GA plasma concentration better fitted with the improvements of both membrane and cytosol parameters following DDS-NHOH treatment, thus evidencing those alterations induced by the two compounds were different and, so, differently affected by GA.
