Ultrasound-assisted extraction of polysaccharides from Syzygium jambos (L.) Alston fruit by deep eutectic solvent and its biological functions

Syzygium jambos (L.) Alston (S. jambos) fruit has been increasingly utilised as a functional food in diabetes management in recent years. As polysaccharides represent a key functional component in fruits with diverse biological activities, studies on extraction methods and antidiabetic effects of S. jambos polysaccharides remain limited. This study established a deep eutectic solvent (DES)-based ultrasound-assisted extraction method for polysaccharides from S. jambos fruit. The optimised extraction conditions determined to be a liquid-solid ratio of 17 mL/g, 6% water content in DES, an extraction time of 50 min, and an ultrasonic power of 200 W in the choline chloride-oxalate DES system (molar ratio of 2:1). The novel extraction method achieved a substantially higher extraction rate than traditional method (32.67% vs. 4.3%), demonstrating the potential for polysaccharides extraction from S. jambos fruits. Additionally, the biological evaluation in vitro revealed that purified polysaccharide TPS-1 moderately inhibited α-glucosidase and α-amylase activities, as well as scavenged DPPH· and ABTS⁺ radicals, suggesting its potential as a dual-functional antidiabetic and antioxidant agent. Moreover, monosaccharide analysis revealed that TPS-1, which comprised mannose, rhamnose, glucuronic acid, and galacturonic acid with a molar ratio of 5.49:11.79:41.25:30.95, differs significantly from the reported water-soluble polysaccharide of S. jambos fruits. However, the structure features of TPS-1 and its antidiabetic effects and mechanisms in vivo remain to be elucidated in future research.