Recovering bioactive compounds from yacon (Smallanthus sonchifolius) using the ultrasonic-microwave-assisted extraction technique

The aim of this study was to recover bioactive compounds from Smallanthus sonchifolius roots, including flavonoids, terpenoids, phenolics, vitamin C, and reducing sugar contents, as well as to examine antioxidant activities using ultrasonic-assisted and microwave-assisted extraction technique. Single-factor experiments were employed to explore the impact of various independent variables, including concentration, extraction method, power, duration, temperature, and pH, on the dependent variables of yacon extraction using the ultrasonic-microwave-assisted extraction method. The Plackett-Burman Design Model was used to screen the parameters that significantly influenced the extraction efficiency. Box-Behnken Design Model was utilized to optimize the ultrasonic-microwave-assisted extracting process to acquire bioactive compounds. The highest yield of total flavonoid contents was obtained with 4.00 of pH, 743.33 W of microwave power, and 39.08°C of ultrasonic temperature. According to reducing sugar contents yield optimization, the optimum conditions were 3.98 of pH, 36.17 seconds of microwave time and 40°C of ultrasonic temperature. To optimize vitamin C concentration, the optimized conditions were 1:40 g/mL of sample-to-solvent ratio, 3.99 of pH, 45.33 seconds of microwave time, and 451.09 W of ultrasonic power. Regarding total terpenoids yield, optimized conditions for extracting were 1:40 g/mL of sample-to-solvent ratio, 2.48 of pH, 30.49 seconds of microwave time, and 49.48 °C of ultrasonic temperature. Under optimized conditions, the recovery yield of flavonoid, terpenoid, vitamin C, and reducing sugar contents were 7.95 mg rutin equivalents/g, 47.93 mg ursolic acid equivalents/g, 107.78 mg ascorbic acid/g, and 230.39 mg D-glucose equivalents/g, respectively. Ultrasonic-microwave-assisted extraction showed significantly higher performance than singular extracting methods and is regarded as a sustainable and effective approach to recover target compounds from yacon roots.