Antioxidant and immunomodulatory activities of <i>Rehmannia glutinosa</i> extracts obtained with complex enzymes and ultrasonic wave

The comprehensive exploration and utilization of plants with both medicinal and culinary applications are crucial for human disease prevention and health maintenance. In this study, extracts of <i>Rehmannia glutinosa</i> were prepared using a complex enzyme- and ultrasound-assisted method. Bioactivity assays revealed that the <i>R. glutinosa</i> extracts exhibited potent radical-scavenging capabilities against DPPH, ABTS, hydroxyl, and superoxide radicals, with scavenging rates of 88.46% ± 1.35%, 98.90% ± 1.68%, 64.79% ± 1.12%, and 72.96% ± 1.46%, respectively. Furthermore, the extracts significantly protected RAW 264.7 cells from H₂O₂-induced oxidative damage, mitigating its effects and repairing cellular integrity. This was achieved by enhancing the activities of endogenous antioxidant enzymes, including superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px), while concurrently reducing malondialdehyde (MDA) levels. Additionally, the <i>R. glutinosa</i> extracts stimulated the secretion of immune factors (TNF-α, IL-1β, IL-6, and NO) in RAW 264.7 cells in a dose-dependent manner. Although the specific bioactive compounds within the extracts were not isolated or identified in this work, these findings collectively demonstrate the potential of <i>R. glutinosa</i> extracts as a valuable source of natural antioxidant and immunomodulatory ingredients.