Impacts of Ultrasound-Assisted Alkaline Electrolyzed Water Extraction on Efficiency and Bioactivity of Extracts from Sweet Tea

Sweet tea, the leaves of Lithocarpus litseifolius [Hance] Chun, is rich in polysaccharides, flavonoids, and polyphenolic ingredients and can be used as a potential source of valuable plant extracts. The purpose of this study was to evaluate the impact of the combination of ultrasound and alkaline electrolyzed water on the efficiency and bioactivity of extracts from sweet tea. The ultrasound-assisted extraction (UAE) was optimized according to the chemical profiles and bioactivity of sweet tea extracts. The optimal condition was as follows. The weakly alkaline electrolyzed water (WAE) was use as solvent, solid–liquid ratio was 1:30 g/mL, extraction time was 40 min, temperature was 60 °C, and extraction was two cycles. The results showed the yields of total flavonoids, total phenols, total sugars, and total terpenoids which were 132.04 mg/g, 58.73 mg/g, 302.34 mg/g, and 226.76 mg/g, respectively. The extracts obtained from the optimized condition exhibited outstanding antioxidant, hypoglycemic, and angiotensin-converting enzyme inhibition (ACEI) activities. The ultra-high performance liquid chromatography-triple quadrupole tandem mass spectrometry analysis identified 39 bioactive compounds in STE, including 9 phenolic acids, 28 flavonoids, and 2 terpenoids. The correlation analysis revealed that the extraction process significantly influenced the bioactive components of extracts and their bioactivities. This study indicated that the combination of ultrasound and WAE was an efficient method for obtaining biocomponents from sweet tea. The findings lay the groundwork for further processing and utilizing sweet tea extracts.