## 2 Materials and Methods
### Analytical Procedures
#### 2.5.2 Determination of Total Phenolic Content (TPC)  
The total phenolic content (TPC) of the extracts was determined by the Folin-Ciocalteu method previously reported by [PERSON] et al. [28]. Briefly, 200 \(\upmu\)L of suitably diluted extracts or standard, 1 mL of Folin-Ciocalteu reagent (previously diluted 1:10 with deionized water) and 800 \(\upmu\)L of aqueous sodium carbonate 7.5% _w/b_ were mixed in a test tube and  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Ultrasonic-Assisted Extraction** & **Conditions** \\ \hline Pulsed modality: duty cycle per second (DC) & 50\% \\ Extraction solvent & Ethanol:Water (70:30 _w/w_) \\ Dry waste/solvent ratio & 1:40 \\ Amplitude level & 40\% \\ Extraction time & 10 min \\ Extraction temperature & \textless{60 }\({}^{\circ}\)C \\ \hline \hline \end{tabular}
\end{table}
Table 1: UAE experimental condition details.  
vortexed. The mixture was equilibrated in the dark at room temperature for 30 min and then the absorbance was read spectrophotometrically at 760 nm using quartz cuvettes with 1 cm of path length. TPC was calculated using gallic acid as reference standard for the calibration curve (\(R^{2}\) = 0.9887) and results were expressed as milligrams of gallic acid in one gram of dry waste (mg GA/gdry waste). Determinations were replicated for each sample and the averaged results were reported.  
Determination of Total Flavonoid Content (TFC)  
The total flavonoid content (TFC) was estimated following the aluminium chloride colorimetric method [29]. Aliquots of 0.5 mL of lavender extracts or diluted standards (querectin) were mixed with 0.1 mL of AlCl\({}_{3}\), 0.1 mL of CH\({}_{3}\)COONa and 2.8 mL of deionized water. Absorbance of the samples was measured at 415 nm wavelength after 40 min of incubation in the dark at room temperature. Diluted samples of commercial quercetin in a range between 5 and 150 \(\upmu\)g/mL were used as standards for the calibration curve (\(R^{2}\) = 0.9987). Flavonoid concentrations were expressed as mg/g of quercetin equivalents (QE).  
HPLC Analysis  
Reversed phase (RP) chromatography of the studied extracts was performed by using a Kinetex EVO C18 column 25 cm \(\times\) 4.6 mm, 4.7 \(\upmu\)m particle size (Phenomenex Inc., Torrance, CA, USA). The solvent gradient method used 0.1% H\({}_{3}\)PO\({}_{4}\) in water (A) and acetonitrile (B). Gradient (% in A): 0-30 min from 10% to 58% B, 1 min from 58% to 90% B, 5 min isocratic 90% B, 1 min from 90% to 10% B, and 25 min isocratic 10% B [30]. Injection volume was 50 \(\upmu\)L; solvent flow rate was set at 1 mL/min. Detection was performed at 280 and 350 nm wavelength to discriminate between phenols and flavonoids. Peak identification and quantification, when possible, was made using external standards. When identification was no possible, peak concentration was calculated as gallic acid equivalents (mg/g) or as quercetin equivalents (mg/g) for unknown phenols and flavonoids, respectively.  
Statistical Analysis  
Data were analysed using the R environment [31]. Differences in RSA, TPC, and TFC among the studied extracts (TWE, FWE, LEACH) were analysed via analysis of variance using the aov function. Multiple comparisons between extracts were carried out using [PERSON]'s Honest Significance tests with the TukeyHSD function. The same approach was used to analyse differences among lavender extracts in the relative composition of single phenolic compounds and flavonoids as observed through HPLC. Results throughout the text were expressed as means \(\pm\)95% confidence intervals.