*3.2. Colorimetric Indices*

As shown in Table 1, the CIELAB colorimetric parameters *a*\*, *b*\*, the chroma and the Hue angle were significantly affected by the interaction of the CV and S factors. Specifically, for 'Lemon', an increase in *a*\* (+18.43%) and Hue angle (+2.21%) was observed in plants under salt stress, compared to the Control, while *b*\* (−26.49%) and Chroma (23.79%) decreased. In 'Anise' and 'Cinnamon', Salt treatment did not result in significant differences for a\* and Chroma. An opposite trend was observed for the hue angle between the Anise and Cinnamon cultivars. Specifically, compared with Control, the above colorimetric parameter was not affected by salt treatment in 'Anise', while in 'Cinnamon' there was a 1.90% increase.

#### *3.3. Leaf Physiological Parameters*

The CV × S interaction did not result in significant differences for the physiological parameters shown in Figure 4 and Supplementary Table S2. Regardless of the cultivar, compared to the control, salt stress significantly (*p* < 0.001) reduced net CO2 assimilation (ACO2), transpiration (E), and stomatal conductance (gs) by 23.72, 30.95, and 29.16%, respectively. The same parameters were influenced by the mean effect of the cultivar. Specifically, 'Lemon' showed the highest E and gs values compared to 'Anise', but the lowest ACO2 values compared to 'Cinnamon'. On the contrary, the maximum quantum efficiency of photosystem II (Fv/Fm) was solely affected by S. The data in Figure 4 D show that plants under salt stress decreased the Fv/Fm values (3.79%) compared to the control.


**Table 1.** Effect of basil cultivars (CV) and stress (S) on CIELab colorimetric indices.

Data are mean values ± standard error, *n* = 3. Mean comparisons were performed by Tukey HSD test for CV and by *t*-Test for S. Different letters within each column indicate significant mean differences. ns, \*, \*\*, and \*\*\* denote non-significant or significant effects at *p* ≤ 0.05, 0.01, and 0.001, respectively.

**Figure 2.** Effect of Cultivar and Stress on total fresh weight (**A**) and leaf fresh weight (**B**). Data are mean values ± standard error, *n* = 3. Mean comparisons were performed by Tukey HSD test for Cultivar and by *t*-Test for Stress. Different letters indicate significant mean differences. \*\*\* denotes significant effects at *p* ≤ 0.001.

**Figure 3.** Effect of Cultivar × Stress on plant height (**A**), leaf number (**B**), leaf area (**C**), total dry weight (**D**), total dry matter (**E**). Data are mean values ± standard error, *n* = 3. Statistical significance of the CV × S interaction was determined by Tukey HSD test for Cultivar and by *t*-Test for Stress. Different letters indicate significant mean differences. \* and \*\*\* denote significant effects at *p* ≤ 0.05 and 0.001, respectively.

**Figure 4.** Effect of Cultivar and Stress on transpiration (**A**), stomatal conductance (**B**), net CO2 assimilation rate (**C**), and chlorophyll fluorescence (**D**). Data are mean values ± standard error, *n* = 3. Mean comparisons were performed by Tukey HSD test for Cultivar and by *t*-Test for Stress. Different letters indicate significant mean differences. ns, \*, and \*\*\* denote non-significant or significant effects at *p* ≤ 0.05 and 0.001, respectively.

#### *3.4. Leaf Pigments*

Chlorophyll a, b, and total chlorophyll concentrations were not affected by the factors considered nor by their mutual interaction, unlike lutein and *β*-carotene (Table 2). The lutein concentration showed significant differences for the mean CV and S. Specifically, 'Lemon' had 25.75% lower lutein concentrations (on average) than the other cultivars. Regardless of the cultivar, salt stress increased the latter carotenoid by 22.85% compared to the control. Compared to the control, the interactions of the 'Anise' and 'Cinnamon' cultivars with salt treatment (Salt) increased *β*-carotene concentration by 39.17 and 47.67%, respectively. The same trend was also observed for antioxidant activity, where salinity increased by 16.18, 44.96, and 23.28% FRAP, DPPH, and ABTS essays, respectively (Figure 5). It should be noted that regardless of the antioxidant activity assay, the highest concentrations were recorded in 'Anise', followed by 'Lemon' and 'Cinnamon'.

**Table 2.** Effect of basil cultivars (CV) and stress (S) on Chlorophylls and carotenoids.


Data are mean values ± standard error, *n* = 3. Mean comparisons were performed by Tukey HSD test for CV and by *t*-Test for S. Different letters within each column indicate significant mean differences. ns and \*\*\* denote non-significant or significant effects at *p* ≤ 0.001, respectively.

**Figure 5.** Effect of basil cultivars and stress on FRAP (**A**), DPPH (**B**), and ABTS (**C**) antioxidant activity. Data are mean values ± standard error, *n* = 3. Mean comparisons were performed by Tukey HSD test for CV and by *t*-Test for S. Different letters indicate significant mean differences. \*\*\* denotes significant effects at *p* ≤0.001.

#### *3.5. Phenolic Acids*

Tables 3 and 4 show the phenolic acid and flavonoid derivatives of basil leaves, respectively, under salt stress.

*Antioxidants* **2022**, *11*, 2207


**Table 3.** Effect of basil cultivars (CV) and stress (S) on phenolic acid derivatives.

mean differences. ns, \*\*, and \*\*\* denote

non-significant

 or significant effects at *p* ≤ 0.01 and 0.001, respectively.


**Table 4.** Effect of basil cultivars (CV) and stress (S) on flavonoids derivatives.

Data are mean values ± standard error, *n* = 3. Mean comparisons were performed by Tukey HSD test for CV and by *t*-Test for S. Different letters within each column indicate significant mean differences. ns, \*\*, and \*\*\* denote non-significant or significant effects at *p* ≤ 0.01 and 0.001, respectively.

As shown in Figure 6A, total phenolics were only affected by the average CV and S effects. Regardless of the stress condition, 'Anise' had the highest concentration of total phenolics (4625.09 mg kg−<sup>1</sup> dw). Compared to the control, salt stress increased total phenolics by 21.63%.

Like total phenols, phenolic acid derivatives and total flavonoids showed a similar trend in response to salt stress (Figure 6B,C). Relative to the mean effect of the cultivar, 'Anise' showed the highest values of total phenolic acid derivatives (Figure 6B), in contrast to total flavonoid derivatives ('Lemon' > 'Anise' > 'Cinnamon'; Figure 6C).

Compared to total flavonoid derivatives, rutin was not significantly affected by the interaction of the factors considered (CV × S), unlike what was observed for dihydroquercetin glucoside and quercitin glucoside. Regarding these glycoside compounds, salt stress increased their concentrations in 'Anise' and 'Cinnamon', while no significant differences were observed in 'Lemon'. In contrast, in 'Lemon', salt stress increased the concentration of quercetin glucoside (35.77 mg kg−<sup>1</sup> dw; Table 4).

Regardless of the factors considered, cichoric acid was the predominant compound, followed by rosmarinic, feruloyl tartaric, salvianolic k, caffeic, salvianolic L, caftaric, salvianic A, chlorogenic, and salvianolic A acids. For chlorogenic, rosmarinic, and feruloyl tartaric acids, the CV × S interaction did not result in significant differences, unlike what was observed for the mean effects (CV and S). Specifically, salt stress, compared to the control, increased the concentrations of the above acids by 16.73, 21.28, and 31.22%, respectively. Relative to the mean effect of the cultivar, 'Anise' recorded the highest concentrations of cichoric and rosmarinic acids, while 'Cinnamon' had the highest content of feruloyl tartaric acid (Table 3).

Similarly to the findings for the above phenolic acids, the CV × S interaction was not significant for salvianolic K, salvianolic L, and chlorogenic acids. However, salt stress significantly increased the concentrations for the acids mentioned above compared to the control. Regardless of stress, 'Anise' was characterized by the highest concentration of salvianolic L and chlorogenic acids, contrary to what was observed for salvianolic K acid, which did not show a significant difference between cultivars (Table 3).

**Figure 6.** Effect of basil cultivars and stress on total phenolics (**A**), total phenolic acid derivatives (**B**), and total flavonoid derivatives (**C**). Data are mean values ± standard error, *n* = 3. Mean comparisons were performed by Tukey HSD test for CV and by *t*-Test for S. Different letters indicate significant mean differences. \*\*\* denotes significant effects at *p* ≤0.001.

Unlike what was observed for the cichoric, rosmarinic, feruloyl tartaric, salvianolic K, caffeic, and salvianolic L acids, the concentrations of caftaric, salviananic acid A, chlorogenic, and salvianolic A acids were significantly affected by the CV × S interaction.

Salt stress increased salvianolinic acid A concentration in all cultivars, with the highest values obtained by Anise × Salt (16.68 mg kg−<sup>1</sup> dw). The same interaction also resulted in the highest concentration of caftaric (81.68 mg kg−<sup>1</sup> dw) and caffeic acids (140.57 mg kg−<sup>1</sup> dw). In 'Anise' and 'Cinnamon', compared with the control, salt stress increased salvianic acid A concentrations by 32.36 and 15.50%, in contrast to 'Lemon', which did not show a significant difference.
