Ultrasonic-assisted extraction and antioxidant activity of polysaccharides from Eucommia ulmoides leaf

Eucommia ulmoides is valuable medicinal plant in China. In this study, ultrasonic technology was used to extract polysaccharides and orthogonal design was applied to choose the optimal extraction conditions. The optimal extraction conditions of E. ulmoides polysaccharides were made up of the ratio of water to raw 30, extraction time 80 min, extraction temperature 60°C and extraction power 200 W. Under these conditions, the extraction polysaccharides content reached 164.95 mg/g. In addition, the potential antioxidant activity of crude polysaccharides (Cp) and pure polysaccharides (Pp) was demonstrated by evaluating reducing power assay, DPPH radical-scavenging assay, OH radical-scavenging assay and ABTS radical-scavenging assay. The results showed that E. ulmoides polysaccharides had significantly impact on the scavenging of DPPH radicals, OH radicals and ABTS radicals, expecially in DPPH radicals with an IC₅₀ values of 0.005 mg/mL and 0.011 mg/mL in Cp and Pp, respectively. However, they were less effective in reducing power assay with low IC₅₀ values of 1.091 mg/mL and 1.041 mg/mL separately. These results indicated that polysaccharides from E. ulmoides leaf could be applied as potential antioxidant.