Phosphorylation of Polysaccharides From <i>Lavandula Angustifolia</i> Extracted Using Ultrasound: Characterization, Antioxidant, and Hypoglycemic Activity

Lavandula angustifolia is a plant with medicinal and edible values. In this study, we compared the effects of ultrasound-assisted extraction (UAE), microwave-assisted extraction (MAE), and hot water extraction at different powers on the yield, antioxidant, and antihyperglycemic activity of Lavandula angustifolia polysaccharides (LAP), which were isolated and purified and then subjected to different degrees of phosphorylation modification to obtain three derivatives (PLAP1-3). The physicochemical properties and structural characteristics of LAP and its derivatives were subsequently determined using a series of instruments. In addition, their antioxidant and antihyperglycemic activity were evaluated. The results showed that the optimal extraction power of LAP was 300 W, at which time the yield was 21.51 ± 0.82%, the DPPH radical scavenging rate was 56.76 ± 2.4%, and the α-amylase inhibition rate was 49.95 ± 1.97%, which were significantly higher than those obtained with other powers, MAE and HWE. A series of characterizations fully confirmed the phosphorylation modification of LAP. Phosphorylation improved the antioxidant and antihyperglycemic activity of LAP and was positively correlated with the degree of substitution (DS), where PLAP2 with DS of 1.58 ± 0.23 exhibited strong antioxidant activities, including scavenging of DPPH radicals, ABTS radicals, hydroxyl radicals and superoxide radicals in vitro, and attenuated H₂O₂-induced HepG2 cell damage. In addition, PLAP2 exhibited enhanced inhibitory activity against α-amylase and α-glucosidase and was able to significantly enhance glucose uptake and intracellular glycogen content in insulin-resistant HepG2 cells.