Negative-pressure cavitation coupled with aqueous two-phase extraction and enrichment of flavonoids and stilbenes from the pigeon pea leaves and the evaluation of antioxidant activities

Abstract An efficient extraction method, negative-pressure cavitation coupled with aqueous two-phase extraction (NPC-ATPE), was developed to simultaneously extract and enrich flavonoids and stilbenes from pigeon pea leaves. The main bioactive compounds, cajaninstilbene acid (CSA), longistyline C (LLC), pinostrobin (PI) and pinostrobin chalcone (PIC) were chosen as target compounds. The extraction conditions were optimized using central composite design combined with response surface methodology. The optimized conditions were: concentration of (NH 4 ) 2 SO 4 21% (w/w), concentration of ethanol 23% (w/w) and temperature 30 °C, negative pressure −0.06 MPa, extraction time 30 min and the liquid/solid ratio 1:50 g/mL. The extraction yields of CSA, PI, PIC and LLC reached 10.25, 5.02, 0.53 and 5.22 mg/g, respectively. Furthermore, according to the DPPH, ABTS and FRAP assay, the extracts of NPC-ATPE had significant antioxidant activities with IC 50 value of 0.337 mg/mL, TEAC value of 0.151 mmol/g and FRAP value of 0.266 mmol/g, respectively. The results demonstrated that NPC-ATPE could be an alternative method for natural compounds simultaneous extraction and enrichment in a single step.