## 3 Materials and Methods
### Identification and Quantification of (Poly)phenolic Compounds by UHPLC-ESI-MS\"  
The (poly)phenolic compounds in the sample were extracted according to previous reports [33; 60], with some modifications. A mixture of 150 \(\upmu\)L of extract and 1 mL of acetonitrile acidified with formic acid (2%) was ultrasonicated for 10 min and subsequently centrifuged at 10,480\(\times\)_g_ for 5 min at room temperature. The supernatant was directly injected into the UHPLC-MS system. Aliquots diluted with acidified acetonitrile (1/100 and 1/10,000) were also analyzed to quantify within the linearity range of the reference compounds, avoiding MS signal saturation. The sample was extracted in triplicate.  
The extract of rosemary was analyzed using an Accela UHPLC 1250 equipped with a linear ion trap-mass spectrometer (LTQ XL, Thermo Fisher Scientific Inc., San Jose, CA, USA) fitted with a heated-ESI probe (H-ESI-II; Thermo Fisher Scientific Inc.). Separations were performed using a XSELECTED HSS T3 (50 mm \(\times\) 2.1 mm), 2.5 \(\upmu\)m particle size (Waters, Milford, MA, USA). The volume injected was 5 \(\upmu\)L and the column oven was set to 30 \({}^{\circ}\)C. Two MS experiments were performed in negative mode [21].  
An MS experiment optimized in negative mode for carnosol analysis (experimental condition 1) was carried out using conditions as follows. The MS worked with a capillary temperature equal to 275 \({}^{\circ}\)C and the source heater temperature set to 250 \({}^{\circ}\)C. The sheath gas flow was 50 units, while the auxiliary gas was set to 12 units. The source voltage was 3 kV. The capillary voltage and tube lens were \(-\)49 and \(-\)148 V, respectively. Elution was performed at a flow rate of 0.3 mL/min. The gradient started with 99% of 0.1% aqueous formic acid, isocratic conditions were maintained for 1 min, and then a 13-min linear gradient from 1% to 40% acetonitrile with 0.1% formic acid was applied. From 14 to 27 min the acidified acetonitrile was increased to 99%, followed by 2 min of 99% acetonitrile, and 6 min at the start conditions to re-equilibrate the column. Analyses were carried out using full scan mode, data-dependent MS\({}^{3}\) scanning from \(m/z\) 100 to 1500, with collision induced dissociation (CID) equal to 35 (arbitrary units). Pure helium gas was used for CID.  
In a second experimental framework, the MS worked with conditions optimized for rosmarinic acid analysis (experimental condition 2). Since the ionization of carnosic acid and carnosol was similar, rosmarinic acid (with diverse ionization/structure characteristics) was selected to optimize the secondary experimental condition in an attempt to cover a wider range of phenolic structures. The capillary temperature was set to 275 \({}^{\circ}\)C, while the source heater temperature was 50 \({}^{\circ}\)C. The sheath gas flow was 40 units, while auxiliary and sweep gas flow were set to 5 and 0 units, respectively. The source voltage was 4 kV. The capillary and tube lens voltage were \(-\)26 and \(-\)78 V, respectively. Analyses were carried out using full scan mode, data-dependent MS\({}^{3}\) scanning from \(m/z\) 100 to 1500, with CID equal to 30 (arbitrary units). The chromatographic conditions were identical to those used for Experimental Conditions 1.  
Quantification was performed in selected ion monitoring (SIM) mode by selecting the relative base peak at the corresponding mass to charge ratio (\(m/z\)) under Experimental Conditions 1.