Phenolic acid and flavonol water extracts of Delonix regia red flowers

Traditional healthy beverages in several African counties were home-made by water extraction of flowers of Delonix regia (Boj.) Raf. This tree belongs to the local biodiversity of plants used in the local medicine. It is also part of the traditional bioproducts marketed within African village communities. Scaling-up at pilot plant level, by mimicking this local recipe, lead to concentrated bioproducts containing various natural phenolic compounds, most of them have never been yet published. A three-steps process was used to prepare concentrated of water-extracted soluble phenolics. This process included: phenol extraction of dried plant by overnight diffusion in acidified water, clarification then concentration of the macerate, using membrane technology. Total phenol contents were determined as gallic acid equivalents using the Folin–Ciocalteu method. Total flavonoid contents, as delphinidin equivalents, were determined using the UV–vis colorimetric method. Comparison of concentration factors of both phenol families (phenolic acids and flavonols) contained in the 3 co-products obtained during the process were made between crude extracts, cross-flow microfiltration extracts and reverse osmosis concentrated extracts. Individual phenol compounds found in the products obtained were characterized and quantified by HPLC-DAD and by HPLC–MS2. Among the 11 phenol compounds identified in the water-extracts, 3 have been already identified in the literature (2 phenolic acids and 1 flavonol), and 8 new compounds, in noticeable amounts, have never been cited. We have confirmed the presence of phenolic acids such as 3,4,5-trihydroxybenzoic (gallic acid), 3,4-dihydroxybenzoic (protocatechuic acid) and of quercetin. We have characterized for the first time the presence of 2-hydroxy 5-[(3,4,5 trihydroxyphenyl) carbonyl oxy] benzoic acid and of 7 other flavonols belonging to the quercetin, kaempferol and isorhamnetol compound families. Using both LCMS and NMR analyses, they have been identified and quantified as: rutin, quercetin 3-O-glucoside, quercetin 3-O-galactoside, quercetin trihexoside, quercetin 3-O-robinobioside, kaempferol rhamnosylhexoside and isorhamnetol rhamnosyl-hexoside.

► An eco-friendly process, including coupled-membrane technology, was used to prepare at pilot plant level water-extracts from Delonix regia flowers.
► Rural Africa communities use to prepare at home this traditional beverage. They believe it to contain natural compounds good enough to cure some people illness.
► To now, very few is known about polyphenol content: 11 newly acid-phenols and flavonols were identified for the first time.