Optimization of ultrasound-assisted extraction of natural pigments from Bougainvillea glabra flowers

• Natural pigments were extracted from Bougainvillea glabra flowers.
• Four factors three level Box-Behnken experimental design was used in this study.
• Individual and interactive effect of process variables was studied on responses.
• Numerical optimization method was adopted to find out the optimal condition.

In this study, ultrasound-assisted extraction (UAE) technique was used to examine and optimize the natural pigment extraction from Bougainvillea glabra flowers using four factors three level (extraction temperature, ultrasonic power, extraction time and solid–liquid ratio) Box-Behnken response surface design. From the results, second-order polynomial models were derived for the responses which were well correlated with experimental data (R2 > 0.98). From response surface plots, extraction temperature, ultrasonic power and extraction time exhibited individual and interactive effects on the pigments yield. An extraction temperature of 55 °C, ultrasonic power of 88 W, extraction time of 37 min and a SL ratio of 1:17 g/ml were identified as optimal condition. Under this condition, the actual yield of (betacyanin of 1.72 ± 0.001 and betaxanthin of 5.78 ± 0.23 mg/g) pigments was acquired and well correlated with predicted values (betacyanin was 1.76 mg/g and betaxanthin was 5.81 mg/g).