Optimization on microwave-assisted alkali-solution and acid-isolation extraction of protein from Euryale ferox and its antioxidant activity

The microwave-assisted alkali-solution and acid-isolation extraction of protein from Euryale ferox was studied using the extraction rate of protein as the index.The influence factors such as pH, temperature, microwave power and microwave time were optimized through the single factor and L₉ ( 3⁴) orthogonal test.The antioxidant activity in vitro of protein was evaluated by DPPH·, ABTS⁺·, ·OH, O₂^-· radical scavenging capability assay. The result showed that the isoelectric point of protein in Euryale ferox was 4.0 and the extraction efficiency was affected in decreasing order by pH, microwave power, microwave time and temperature. The optimum extraction conditions for these four parameters were pH11.5, 400 W, 10 min, and 40 ℃respectively.The maximum extraction yield of protein from Euryale ferox could up to 61.45% and the content of protein was81.5% under the optimized conditions.The proteins had certain scavenging ability on DPPH·, ABTS⁺·, ·OH, O₂^-·free radical with IC₅₀ of 0.985, 0.313, 0.872, 0.926 mg/mL, but less than V_C's ability to remove them.