Abstract:

In this study, the microwave-assisted extraction of polysaccharides from Macadamia integrifolia shell was
optimized, and the antioxidant properties of the extracted polysaccharides were determined. Optimization of extraction
parameters for improved extraction efficiency of polysaccharides was done using single factor experiment and an orthogonal
array design L9 (33). Meanwhile, the antioxidant activities were evaluated by hydroxyl, 1,1-diphenyl-2-picrylhydrazyl
(DPPH) and superoxide anion free radical scavenging assays. The optimum extraction parameters were determined as
follows: microwave power, 200 W; microwave irradiation time, 2.5 min; and solid-to-solvent ratio, 1:50 (g/mL). Under
these conditions, the average extraction yield of polysaccharides was 0.70%. At a polysaccharide concentration of
0.027 5 mg/mL, the percentage scavenging of ·OH, DPPH free radical and O2-· were 63.11%, 61.90% and 80.09%,
respectively, implying that these polysaccharides have good ability to scavenge ·OH, DPPH free radical and O2-·.

Key words: Macadamia integrifolia shell, microwave-assisted extraction, polysaccharide, antioxidant properties