Extraction optimization of raspberry proanthocyanidins and determination of its antioxidant activities in vitro

The isolation of proanthocyanidins from raspberries and their antioxidant activity remains an ongoing challenge. Optimization of ultrasound-assisted extraction method of raspberry proanthocyanidins by response surface analysis. Assessment of the effect of AB-8 macroporous adsorption on obtaining proanthocyanidin monomers of different composition and evaluation of their antioxidant activity. Determination of protective effects of proanthocyanidins by cell proliferation assay. Under the optimized extraction conditions of 60% ethanol, material-to-liquid ratio of 1:30, ultrasonic extraction temperature of 44 degrees C, time of 2 h, and power of 450 watts (W), the yield of proanthocyanidins was 0.914%. The four separated proanthocyanidins, D1, D2, D3, D4, showed dose-dependent antioxidant activities, with D2 having the best antioxidant effect. 100 mu g/ml of D2 could scavenge above 90% free radicals and achieve above 85% of human cell survival rate. The identified extraction conditions and antioxidant activities may drive the development of potential health-promoting ingredients.