The Evaluation of the Phytochemical Profiles and Antioxidant and α-Glucosidase Inhibitory Activities of Four Herbal Teas Originating from China: A Comparative Analysis of Aqueous and Ethanol Infusions

Recent research has demonstrated the positive impact of herbal tea consumption on postprandial blood glucose regulation. This study conducts a comparative analysis of aqueous and ethanol extractions on four herbal teas (Mallotus, Cyclocarya, Rubus, and Vine) to assess their phytochemical profiles and functional attributes. Phytochemical contents, antioxidant activities, alpha-glucosidase inhibitory activities, and chemical compositions are investigated via colorimetric analyses and UPLC-Q-Orbitrap HRMS/MS, respectively. Results indicate that Vine, among the teas studied, exhibits the most pronounced glucose-regulating effects under both extraction methods. While ethanol extractions yield higher phytochemical content overall, the compositions vary. Conversely, aqueous extracts demonstrate unexpectedly potent antioxidant activities and comparable alpha-glucosidase inhibitory activities to ethanol extracts. Phytochemical contents correlate positively with antioxidant activities and alpha-glucosidase inhibitory activities. However, antioxidant activities exhibit a weak positive correlation with alpha-glucosidase inhibitory activities. These findings provide evidence that aqueous extracts from herbal teas contain valuable phytochemical compositions beneficial for antioxidants and individuals with hyperglycemia, suggesting their potential as functional ingredients to enhance the nutritional value of herbal food products.