# Phenolic and Volatile Composition of a Dry Spearmint (_Mentha spicata_ L.) Extract
## Results and Discussion
### Characterization of the Phenolic Profile

Table 1: _Cont._The 54 compounds tentatively identified according to their mass spectral behaviour were quantified by comparison with reference compounds selected based on structural similarity and considering that the functional groups may strongly affect their ionisation properties (i.e., salvianolic acid J was quantified as salvianolic acid A, salvianolic acid E as salvianolic acid B, danshensu and its derivatives as caffe acid, etc.). Accordingly, in this case, data reported in Table 2 must be considered as semi-quantification. Nevertheless, some compounds responded to the electro-spray ionisation in a unique manner relative to the reference standards used or did not reach the limit of quantification (LOQ) of the corresponding reference compound; therefore, they were not quantified to avoid miscalculation of the phenolic content of the spearmint extract. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**ID**\({}^{\text{a}}\) & **Compounds** & **Quantified as \(\ldots\)** & **Concentration (mg/g)** \\ \hline
4 & Dihydroxyphenyllactic acid (Danshensu) & Caffeic acid & 0.77 \(\pm\) 0.09 \\
5 & Protocatecuic acid hexoside & Caffeic acid & 0.04 \(\pm\) 0.00 \\
7 & Hydroxybenzoic acid & Caffeic acid & 0.57 \(\pm\) 0.07 \\
8 & Caffeic Acid & Caffeic acid & 2.18 \(\pm\) 0.30 \\
9 & Hydroxyphenyllactic acid & Caffeic acid & 0.07 \(\pm\) 0.00 \\
10 & Luteolin-8-C-glucose (orientin) & Luteolin-4-glucose & 0.02 \(\pm\) 0.00 \\
11  
The total amount of phenolic compounds of the evaluated spearmint extract calculated on the basis of UHPLC-ESI-MS\({}^{\text{n}}\) data was 262.97 \(\pm\) 15.90 mg/g, which was in agreement with [PERSON] et al. [7], who reported a total phenolic content for _Mentha spicata_ L. (spearmint) extract of 214 mg/g, expressed as gallic acid equivalents. More specifically, the sum of rosmarinic acid and other rosmarinic acid derivatives (such as sagerinic acid) in this extract was about the 88% (230.50 \(\pm\) 13.50 mg/g) of the total amount of detected phenolics, followed by the sum of salvianolic acids (5.6% of total phenolics, 14.70 \(\pm\) 1.19 mg/g) and caffeoylquinic acids (1.2% of total phenolics, 3.06 \(\pm\) 0.27 mg/g). Hydroxycinamic acids, including catfaric acid (an ester of caffeic and tartaric acids), represented about 1.1% of total phenolics (3.00 \(\pm\) 0.36 mg/g). All of the other detected phenolic groups, such as flavonoids, flavanones, flavones, hydroxybenzoic acids, and hydroxyphenylpropanoic acids represented approximately 1% of the total amount of phenolic compounds (0.01 to 0.99 mg/g). Among the detected compounds, rosmarinic acid, a caffeic acid dimer, was identified by comparing the mass spectra obtained for the sample with those registered for a rosmarinic acid standard solution. This compound occurred at the highest concentration (173.76 \(\pm\) 11.52 mg/g) and is approximately four-fold higher than the 4.6 mg/g reported for other water extracted spearmint lines [7]. Differences in the amount of rosmarinic acid of this extract with respect to other spearmint extracts are likely due to the selective-breeding techniques used for its production. However, rosmarinic acid concentrations could vary due to seasonal growth or extraction procedures. Rosmarinic acid is known to exert anti-inflammatory activities mainly due to its ability to inhibit lipoxygenenses and cyclooxygenenses, but it has also been shown to have anti-acetylcholinesteraseerase, antioxidant, and antibacterial capabilities [28; 29; 30]. Furthermore, it was possible to observe the presence of several rosmarinic acid derivatives. In particular, significant amounts of sagerinic acid (8.93 \(\pm\) 1.10 mg/g) and an isomer of sagerinic acid (peak 41; 40.05 \(\pm\) 2.20 mg/g) were found. This is consistent with results obtained from analysis of lemon balm extracts [25], but have not been reported in the literature in water-extracted spearmint to date. Other polar compounds in the spearmint extract included additional caffeic acid derivatives, such as salvianolic acids.