Physicochemical properties and anti-oxidation activities of ulvan from Ulva pertusa Kjellm

Abstract

The present study investigated the effect of extraction conditions (including hot water-HW, ultrasonic assisted-UA, enzyme assisted-EA and ultrasonic-enzyme assisted-UEA) on the yields, chemical composition, rheological properties and antioxidant activities of ulvan. The yields obtained by the above four extraction methods ranged from 17.88% to 26.77%. The use of enzymes helped to improve the yields of extraction, and through ultrasonic-enzyme treatment, the maximum yield was obtained (26.7%). It was found that ulvan primarily consisted of sugar (41.9%–51.3%), uronic acid (14.1%–19.7%), protein (2.4%–3.3%) and ash (21.2%–24.9%), and the neutral sugars largely comprised rhamnose (22.4%–29.5%), xylose (10.0%–13.3%), glucose (5.0%–8.2%) and galactose (0.3%–0.5%). The results of the rheological measurements revealed that ulvan (4%, w/w) extracted by enzyme-assisted, ultrasonic-enzyme-assisted, ultrasonic-assisted and hot water treatment exhibited the stable shear viscosities of 24.5, 29.2, 56.7 and 95.2 mPa·s, respectively. Furthermore, ulvan extracted by enzyme-assisted and ultrasonic-enzyme-assisted treatment showed visible DPPH radical scavenging ability over that extracted by hot water extraction and ultrasonic-assisted treatment, especially that extracted by enzyme-assisted treatment (SC50 6.52 mg/mL). Overall, the physicochemical properties of ulvan could be significantly affected by extraction methods. Polysaccharide from Ulva pertusa Kjellm, for its anti-oxidation activities, has high application implication in the field of healthcare, and subsequent researches should discuss its bioactive functions.