Ultrasonic/microwave-assisted extraction and properties of polysaccharides from Elaeagnus angustifolia

This study aimed to optimize the ultrasonic/microwave-assisted extraction (UAME) technique of Elaeagnus angustifolia polysaccharides (EAP-UM) by response surface methodology (RSM). The optimum conditions include: solid-liquid ratio of 1:23 g/mL, ultrasonic power of 252 W, microwave power of 417 W, and extraction time of 11 min. Under these conditions, the yield of polysaccharides reached 7.87%, superior to ultrasound-assisted extraction (UAE, 5.74%), microwave-assisted extraction (MAE, 6.86%), and hot water extraction (HWE, 4.91%). UAME could also result in higher carbohydrate, protein, and uronic acid contents compared to other methods. The properties of EAP-UM were further analyzed by infrared spectra (IR) and scanning electron microscopy (SEM). Moreover, EAP-UM exhibited a remarkable free radical scavenging ability (DPPH, IC50, 79 µg/mL) and reduced power. EAP-UM also showed α-amylase inhibiting activity (IC50, 2.826 mg/mL). UAME has the advantage of high extraction rate and short extraction time, and the obtained polysaccharide EAP-UM had better properties. These findings may serve as a reference for the development and application of E. angustifolia.