Optimization of anthocyanin, flavonol and phenolic acid extractions from Delonix regia tree flowers using ultrasound-assisted water extraction

Flowers of Delonix regia trees from Ivory Coast are traditionally macerated in water to prepare beverages with beneficial health properties mainly due to their polyphenolic contents. Different maceration procedures, mimicking the traditional process, were compared on the basis of polyphenol content followed by HPLC-DAD analysis. Under optimized maceration ratio (R = plant sample weight/maceration media volume), plant extractions were compared, including acidified-water-based media and assisted-ultrasound or stirring extraction procedures. Diffusion kinetics of polyphenol families (anthocyanins, flavonols and phenolic acids) were followed by HPLC and lead to find optimum ratio (R = 1/100). Flavonol contents were 28.5, 31, and 33.5 μmol g−1 (expressed as quercetin equivalent), using acidified-water (0.01N) media with sulphuric or citric acids. Anthocyanin and phenolic acid contents were within the same range for these water media (5.6 μmol g−1 as cyanidin equiv. and 27.5 μmol g−1 as gallic acid (GA) equiv., respectively). Ultrasound-assisted procedure shortened maceration time (three times shorter) but did not show higher level of total polyphenol than stirring-assisted procedure (39 μmol g−1 GA equiv.). This eco-friendly and low-cost extraction process will provide to African people, with safer quality and longer availability, polyphenol-rich bio-products.