Optimization of ultrasonic-assisted hot acidic solvent extraction of ulvan from Ulva intestinalis of the Persian Gulf: Evaluation of structural, techno-functional, and bioactivity properties

This study was aimed at the optimization of extraction, structure characterizing and determination of the techno-functional and bioactivity properties of ulvan from Ulva intestinalis. At first, six extraction techniques including hot water, hot acidic and hot alkaline solvent extraction, as well as microwave, autoclave and ultrasonic-assisted hot water extraction were investigated, and the methods of acidic and ultrasonic were selected for further optimization. Optimal conditions of ultrasonic-assisted hot acidic solvent extraction with a maximum efficiency of ∼26.77% were determined as follows: 86 °C, 34 ml g−1, pH 4.5 and 200 W. According to the structure characterizing examinations, ulvan predominantly consisted of carbohydrates, sulfates, and proteins. As expected, the main monomers were rhamnose, glucuronic acid, glucose and xylose respectively. FT-IR spectroscopy confirmed that ulvan was composed of acidic and neutral sugars containing α-configuration in pyranose form. The average molecular weight of ulvan was calculated to be around 1200 kDa. According to TGA, the main stage of polysaccharide degradation commenced at about 210 °C. Ulvan had satisfactory performance in techno-functional analyses, which indicates its applicability in food and cosmetic systems. In bioactivity assays: this polysaccharide had a remarkable scavenging activity on DPPH (up to 73.24%) and ABTS+ (up to 94.94%) radicals and showed good inhibition effects on three bacterial strains including E. coli, S. typhimurium and B. subtilis. Finally, its impressive and satisfactory antiproliferative effects towards Cell lines of HDFn and SK-MES-1 were evidenced. The overall findings indicated the great potency of ulvan for pharmaceutical and food applications.