Optimisation of ultrasound-assisted extraction conditions for maximal recovery of active monacolins and removal of toxic citrinin from red yeast rice by a full factorial design coupled with response surface methodology

•A practical method of ultrasonic extraction was developed in red yeast rice.•Response surface methodology was used to optimise the process variables.•This method reached maximal recovery of monacolins and removal of toxic citrinin.•This method may be applied for industrial in manufacturing of monacolins.

This study optimised the ultrasound-assisted extraction (UAE) conditions to achieve maximal recovery of active monacolins with minimal contents of citrinin from red yeast rice (RYR). A central composite design after a full factorial design was utilised to examine the different UAE parameters. The studies revealed that HAc%, extraction time and EtOH% had significant influences on the recovery yield of monacolins, while HAc% and EtOH% were key factors for the elimination of citrinin. The resulting optimal conditions were as follows: ultrasound power of 250 W, HAc% of 7.7%, RYR amount of 0.2 g (solvent-to-solid ratio 40 mL/g), extraction time of 50.7 min, EtOH% of 57.2% and extraction temperature of 20 °C. Under these conditions, at least 94.7% of monacolins was recovered and 87.7% of citrinin was removed from RYR. This optimised UAE condition was further evaluated for potential industrial application in manufacturing of RYR as pharmaceuticals and nutraceuticals.