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.