Ultrasonic-assisted extraction (UAE) was used to extract proanthocyanidins (PC) from Spatholobus suberectus Dunn. Response surface methodology (RSM)

based on a three-factor

three-level Box-Behnken central composite design (BBD)

was employed to obtain the optimal extraction parameters

in which the extraction yields of PC was maximum. Three important factors

including extraction time

solidliquid ratio and acetone concentration

were selected by single-factor tests. Optimized extraction conditions for PC were a ratio of liquid to solid of 1∶45 mL/g

25 ℃

30 min

and acetone concentration as 70%

one-time extraction

500 W ultrasonic power. Under these conditions，the extraction yield of PC was 25.58%. In DPPH· and ABTS· scavenging assays

the IC

50

of PC from S. suberectus were 8.42 μg/mL and 10.55 μg/mL

respectively.