Optimization of ultrasonic-assisted extraction for monacolin K, antioxidant activity, pigment and citrinin of monascal waxy corn by response surface methodology

Abstract

This study aims to investigate the ultrasonic extraction optimization of monascal waxy corn (MWC). An optimization procedure using a central composition design with two factors (ethanol concentration and temperature) consisting of 13 experimental runs with five replicates of the central points was applied and a second-order polynomial model was used to describe the effects of these parameters on extraction for monacolin K content, antioxidant activities, pigment intensity and citrinin content. The optimized conditions were 69.91% ethanol/49.95°C (monacolin K); 69.62% ethanol/49.15°C (DPPH); 70.67%ethanol/ 49.90°C (chelating ability on Fe²⁺); 70.91% ethanol/50.80oC (Pigment); 85.00% ethanol/60^oC (citrinin) with corresponding yields of 348.72 mg/kg dry weight; 2.65 mmol Trolox/ml; 96.76%; 4072.45 unit/g dry weight and 2.04 μg/kg dry weight, respectively. The maximal monacolin K content predicted by response surface analysis was 349.59 mg/kg dry weight. The experimental value was close to those predicted values, showing fitting of the model (R² = 0.924) applying RSM for optimizing the ethanol concentration and temperature on monacolin K content from MWC.