Optimization of microwave-assisted extraction of betalains from red beet (Beta vulgaris) and evaluating the antioxidant activity of obtained extract

Abstract
Background and objective: Microwave-assisted extraction (MAE) is one of the novel, fast, and efficient methods for extraction of bioactive compounds. The aim of this study was optimization of MAE of betalains from red beet (Beta vulgaris) and evaluating antioxidant activity of its methanolic extract.
Materials and methods: The effects of independent variables namely, microwave power level (100-300 W), extraction time (1-15 min), and liquid-to-solid ratio (10-30 ml/g) were investigated on total extraction yield, free radical scavenging activity, phenolics, flavonoids, and betalains (betaxanthin and betacyanin) contents using central composite design.
Results: According to obtained results, the total phenolic, flavonoid, and betalains contents were significantly decreased by increasing extraction time. Simultaneous increase of microwave power level and liquid-to-solid ratio resulted in significant increase of total phenolic, flavonoid, and betalains contents (p0.05). The optimized condition of MAE of phenolics, flavonoids, and betalains was microwave power level of 300 W, liquid-to-solid ratio of 30 ml/g, and extraction time of 1 min. In contrast, simultaneous increase of microwave power level and liquid-to-solid ratio resulted in significant decrease of total extraction yield (p0.05). The optimized condition of the highest total extraction yield was microwave power level of 100 W, liquid-to-solid ratio of 10 ml/g, and extraction time of 15 min.
Conclusion: We can apply MAE method for extraction of bioactive compounds at shorter extraction time and energy saving.

Abstract
Background and objective: Microwave-assisted extraction (MAE) is one of the novel, fast, and efficient methods for extraction of bioactive compounds. The aim of this study was optimization of MAE of betalains from red beet (Beta vulgaris) and evaluating antioxidant activity of its methanolic extract.
Materials and methods: The effects of independent variables namely, microwave power level (100-300 W), extraction time (1-15 min), and liquid-to-solid ratio (10-30 ml/g) were investigated on total extraction yield, free radical scavenging activity, phenolics, flavonoids, and betalains (betaxanthin and betacyanin) contents using central composite design.
Results: According to obtained results, the total phenolic, flavonoid, and betalains contents were significantly decreased by increasing extraction time. Simultaneous increase of microwave power level and liquid-to-solid ratio resulted in significant increase of total phenolic, flavonoid, and betalains contents (p0.05). The optimized condition of MAE of phenolics, flavonoids, and betalains was microwave power level of 300 W, liquid-to-solid ratio of 30 ml/g, and extraction time of 1 min. In contrast, simultaneous increase of microwave power level and liquid-to-solid ratio resulted in significant decrease of total extraction yield (p0.05). The optimized condition of the highest total extraction yield was microwave power level of 100 W, liquid-to-solid ratio of 10 ml/g, and extraction time of 15 min.
Conclusion: We can apply MAE method for extraction of bioactive compounds at shorter extraction time and energy saving.