Effect of extraction techniques on anthocyanin from butterfly pea flowers (Clitoria ternatea L.) cultivated in Vietnam

The butterfly pea flower (Clitoria ternatea) has attracted much interest recently due to its potential application as a source of natural food colorings and antioxidants. Along with conventional methods, this study applied ultrasound and microwave techniques in the extraction of natural pigments, as well as bioactive compounds. For this purpose, ultrasound-assisted extraction (UAE) (temperature 60oC–80oC, time 15–60 minutes, solid-toliquid ratio 5:100 (g/ml), 490 W, and 42 kHz frequency), microwave-assisted extraction (MAE) (microwave’s power levels 200–600 W, time 3–6 minutes), and conventional extraction (CE) (temperature 60oC–80oC, time 15–60 minutes) were applied. The results showed a significant (p < 0.05) effect of MAE and UAE on anthocyanins and antioxidant activities ferric reducing antioxidant power (FRAP) of butterfly pea flowers extract in comparison with CE. The MAE and UAE methods improved anthocyanin yield by 14.11% and 15.01% with the highest total anthocyanin content obtained by UAE (70oC and 5 minutes). Multiple regression analysis was performed to select the optimal parameters by UAE (74oC for 56.88 minutes) with the highest concentration of anthocyanins (39.90 mg/l) and FRAP (μMFeSO4/100 ml) in the extract. Five anthocyanin compounds, delphinidin-hex, cyanidin-hexose-deoxyHex, delphinidin-deoxyhex-hex, cyanidin-hexose-2 deoxyHex, and delphinidin-hexose-2 deoxyHex, were identified in the extract.