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

Plantaginis Semen (PS) are the dried mature seeds of Plantago asiatica L. or Plantagodepressa Willd. in the Plantago family. Its polysaccharides are important components of PS. 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.