Phytochemical, antioxidant activity, and thermal stability of Clitoria ternatea flower extracts

<br />The demand for beneficial, safe natural pigments is growing. <i>Clitoria ternatea</i> (CT) flowers are a promising source of natural blue colours and bioactive compounds. This study extracted intact CT flowers (CTFs) and their powders (CTFPs) with distilled water at various temperatures (30–90 °C) and durations (30–180 min). The total anthocyanin content (TAC) and total phenolic content (TPC) of the CT extracts were analysed by using the pH differential and Folin-Ciocalteu methods, respectively. The antioxidant activity was expressed as the ability to scavenge DPPH (2,2-diphenyl-1-picrylhydrazyl) radicals. The results showed that different sample types significantly (<i>P</i> < 0.05) influenced the TAC, TPC, and antioxidant activity. The optimal TAC and TPC extraction for CTF was at 90 °C for 90 min, and for CTFP at 90 °C for 30 min. Using hot water instead of 60% alcohol organic solvent was feasible for extracting the phytochemicals, particularly with CTF. Ultrasound-assisted extraction was notably effective for anthocyanins from intact flowers. Higher heating temperatures and pH values increased the anthocyanin degradation rate constants, while a higher pH decreased the activation energy. Thus, blue aqueous CT flower extracts, rich in phytochemicals and antioxidants, have the potential for use in foods and nutraceuticals with neutral and acidic pH values.