## 3 Results and Discussion  
### Extraction of Antioxidant Bioactive Compounds  
As reported in Figures 1 and 2, UAE caused a rapid increase in the TPC values in both types of SGP, obtaining values of 35.55 \(\pm\) 0.36 mg GAE/g dw for the WP and 27.35 \(\pm\) 0.57 mg GAE/g dw for the RP after the first 15 min of treatment. In monitoring the TPC content extracted from GP using UAE at different amplitudes, [PERSON] and [PERSON] (2019) highlighted that ultrasonic waves act in the first few minutes of extraction, where the cavitational effects in the solvent near the plant materials form microchannels towards the food matrix, resulting in greater penetration. However, over time, the ultrasonic waves exert increased action in breaking down the cell structures, causing some of the extracted constituents to be lost, which can affect the mass transfer capacity, thus decreasing the permeability of the cellular structures to the solvent [20]. The combined WUS treatment led to a major increase in the TPC only in the second half of the treatment duration, i.e., when UAE was introduced. The WUS treatment achieved a TPC that was only slightly higher than that yielded by using UAE for 25 min and 27.5 min for the WP and the RP, respectively, but these differences were not significant (\(p<0.05\)). A comparison of the extraction methods based on statistical analysis is reported in Table S1. When the temperature increases, the yield increases due to the higher porosity of the material; higher solvation; a reduction in the surface tension and viscosity of the extracts; and greater mass transfer. However, a temperature higher than the classic range of 20 to 50 \({}^{\circ}\)C conventionally used in the extraction of polyphenols by maceration can easily lead to hydrolysis and oxidation of many phenolic compounds, especially over prolonged extraction times [21]. Figure 1: Kinetics over time of TPC during hydroalcoholic extraction of bioactive compounds from WP using WB, WUS and UAE methods. Several emerging technologies, including UAE, are more suitable for the extraction of thermolabile substances because they do not primarily exploit thermal energy for extraction [22; 23; 24; 25]. An increase in temperature reduces the intensity of cavitation due to lower surface tension and increased vapor pressure in the cavitation bubbles and, therefore, may reduce the extraction rate. Conducting processes at ambient temperature and pressure also reduces the energy requirements and costs of processing [26]. UAE does not use hazardous chemicals, offers a shorter extraction time and has a high energy efficiency and extraction rate [27]. [PERSON] et al. [28] showed that UAE (55 \(\pm\) 5 kHz, 435 \(\pm\) 5 W/L, cycles of 0.5 s) could extract the total phenolic compounds from RP eight times faster than conventional mechanical agitation (50 \({}^{\circ}\)C, 200 rpm). A study by [PERSON] et al. (2017) [29] corroborated this finding, showing that UAE (20 kHz, 1000 W/L, 28 \(\pm\) 3 \({}^{\circ}\)C) enabled a significantly higher recovery of the TPC in a shorter time compared to both microwave-assisted extraction and conventional mechanical stirring. The TPC in the extracts obtained using UAE was twice as high as that in those obtained using conventional mechanical stirring just 9 min after the start of extraction, demonstrating its superior effectiveness for the recovery of total phenolic compounds. In the present study, in the first 10 min, the TPC extracted from the WP was more than five times higher when using UAE than when applying conventional extraction with the WB, while values more than nine times higher were obtained for the RP. For both SGPs, at 30 min, the TPC obtained using UAE was just over double that when using the WB.