## 4 Discussion  
Studies on the effects of UAE on biological material are abundant [67; 68; 69]. Widely addressed is the issue of the effect of UAE on availability of biological content, such as flavonoids or polyphenols [70; 71; 72]. Herbal teas such as mint, chamomile and others are also often the raw material for research [73]. Ultrasound research can be included in the optimization of extraction processes [74; 75]. Ultrasound may enable the dissolution of essential oils and other tea herbs, which affects the flavor and aroma of the tea. Figure 1: Percentages of extracted macronutrients for different extraction times along with the booster used. Extraction of plant materials has been carried out by various extraction methods. Over the past 50 years, non-conventional methods have been developed that are more ecological and eco-friendly due to shorter operation time, less use of synthetic and organic chemicals, and better yield and quality of the extract. To increase the overall yield and selectivity of bioactive constituents from plant materials, ultrasound [76], pulsed electric field [77], microwave heating [78], enzymatic digestion [79], ohmic heating, supercritical fluids [80, 81] and accelerated solvents ([PERSON]) have been investigated as unconventional methods. In a number of scientific studies comparing different extraction techniques compared to ultrasound-assisted extraction, the advantage of ultrasound is clear. This is mentioned, among others, by [78] in a study comparing the efficiency of extraction of plant raw materials by means of unconventional extraction techniques, including but not limited to ultrasound. The raw materials for the study there were peppermint leaf (_Menthae piperite folium_), age leaf (_Salviae folium_) and dandelion root (_Taraxaci radix_). The results indicated that the use of ultrasonic waves results in an improvement in extraction efficiency, compared to a standard extraction using a Soxhlet apparatus, and that the total energy consumption is lower than in the case of 'hot' extraction. Notwithstanding the increase in yield of the key ingredient, the UV-Vis spectrum demonstrates that the concentration of other, as yet unidentified, substances in the extract is increased using this method. Ultrasound is a method of assisting extraction, whose applicability in the food industry is being extensively investigated as the authors [66] point out as a method for optimizing the extraction of bioactive compounds from the by-products of fruit and vegetable processing. Another example is the extraction of antioxidant polyphenols from green tea (_Camellia sinensis_), where improved extraction efficiency of antioxidant polyphenols from green tea was investigated by combining ultrasound-assisted extraction (UAE) and deep eutectic solvents. The effect of extraction parameters on total phenolic content (TPC) values was also investigated and the liquid-to-solid ratio, ultrasonic power and ultrasonic time were optimized. Optimal extraction conditions included a liquid-to-solid ratio of 36:1 (ml/g), an ultrasonic power of 461.5 W and an ultrasonic time of 21 min, with a highest TPC value of 243 \(\pm\) 7 mg gallic acid equivalent (mg GAE)./g dry matter (sm), which was 13% higher than before optimization. Furthermore, under optimized extraction conditions, the tea polyphenic extract showed higher antioxidant activity compared to conventional extraction methods. Similar results were obtained by the authors for ultrasound-assisted techniques with infusions. [PERSON] and [PERSON] [82] evaluated the effect of ultrasound at different times (10, 20, 30, 40, 50 and 60 min), amplitudes (0%, 10%, 30%, 50% and 70%) and solute/solvent ratios (1:25, 1:50, 1:75 and 1:100) on TPC extraction and radical absorption activity from cold-brewed black tea.