Optimization of ultrasound-assisted deep eutectic solvent extraction, characterization, and bioactivities of polysaccharide from <i>Plantaginis Semen</i>

<i>Plantaginis Semen</i> (PS) are the dried mature seeds of <i>Plantago asiatica</i> L. or <i>Plantagodepressa</i> Willd. in the Plantago family. Its polysaccharides are important components of <i>PS</i>. Response surface methodology was used to optimize the ultrasonic-assisted deep eutectic solvent (DES) extraction process of PS polysaccharides (PSP). The results showed that the optimal extraction parameters were a solid-liquid ratio of 1:35 g/mL, an extraction time of 73 min, and a molar ratio of 2:1. The yield of PSP was 0.64% and 1.20% by water immersion and ultrasonic water extraction, respectively, indicating that the DES extraction method (2.21 ± 0.06%) is superior to these two methods, and the optimization effect is good. Through the α-glucosidase and α-amylase inhibition activities experiment, it was found that the IC₅₀ values of PSPs-1 were 1122 and 220.5 μg/mL. DPPH·and ABTS⁺ scavenging activity experiments showed that the IC₅₀ values of PSPs-1 were 19.2 and 4.3 μg/mL, respectively. Its molar ratio of monosaccharide composition is rhamnose: galactose: galacturonic acid: glucose: glucuronic acid: arabinose: mannose: xylose = 33.6:13.3:6.5:3:2.6:2:1.4:1. Therefore, this study can provide an experimental basis for the establishment of an industrialized production process of polysaccharides and the study of their biological activities.