Optimization by response surface methodology of ultrasound-assisted extraction and antioxidant activities of polysaccharides from Glechoma longituba (Nakai) Kupr.

In this study, we optimized the ultrasound-assisted extraction of polysaccharides from the dried aboveground part of Glechoma longituba(Nakai)Kupr. by response surface methodology (RSM) based on central composite design and measured the antioxidant activities of the extracted polysaccharides using 1,1-diphenyl-2-picrylhydrazyl (DPPH·) scavenging, 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid (ABTS+·) radical scavenging, Fe2+chelating activity, ferric reducing antioxidant power (FRAP), and N,N-dimethyl-p-phenylenediamine radical scavenging methods. The optimal extraction conditions were obtained as follows: pH, 7.2; liquid-to-solid ratio, 32:1 (mL/g); ultrasonic power, 270 W; and ultrasonic time, 8 min. Under these conditions, the yield of polysaccharides was 4.95%-5.12%. The extracted polysaccharides exhibited powerful antioxidant activities. The DPPH and ABTS+·radicals scavenging activities, Fe2+chelating activity, FRAP value and DMPD radical scavenging capacity were (0.51 ± 0.04) μmol Trolox equivalent (TE)/mg, (0.69 ± 0.04) μmol TE/mg, (0.51 ± 0.29) μmol EDTA-2Na equivalent (EE)/mg, (3.45 ± 0.03) μmol TE/mg and (0.17 ± 0.01) μmol TE/mg, respectively. © 2016, China Food Publishing Company. All right reserved.