Abstract:

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)
radical scavenging, 2,2’-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid radical (ABTS+·) 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 radicals and ABTS+· 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.

Key words: Glechoma longituba (Nakai) Kupr., polysaccharides, ultrasound-assisted extraction, response surface methodology, antioxidant activity