Optimization of Ultrasonic-Assisted Extraction of Polyphenols in the Purple Passionfruit Leaves by Response Surface Methodology and Its Antioxidant Activity

To optimize the extraction technology and antioxidant activity of polyphenols from purple passionfruit leaves. On the basis of a single factor test,the material to solvent ratio,extraction time,ultrasonic power and ultrasonic temperature were the factors,and the Box-Beheken was used to design test program. The optimal extraction technology was as follows: Solvent to material ratio 36∶1 mL/g,extraction time 54 min,ultrasonic power 350 W and temperature 70 ℃. Under the above conditions,the extraction amount of polyphenols from purple passionfruit leaves was(13.19±0.17) mg/g. The test of antioxidant activity showed that the polyphenols from purple passionfruit leaves had better antioxidant activity,and half inhibition concentrations(IC₅₀)of DPPH and hydroxyl radicals were 0.058 mg/mL and 0.144 mg/mL,respectively.