Polyphenol extraction and characterization of Justicia secunda Vahl leaves for traditional medicinal uses
Water extracts of Justicia secunda leaves are used by village communities in southern countries to prepare traditional medicines at home. The beverage is usually obtained by boiling the plant in water. On a pilot plant scale, water extracts were processed using an extraction-concentration procedure achieved in a three-step process, including ultrasound-assisted water extraction followed by cross-flow microfiltration of the crude extract and its concentration by reverse osmosis. As the processing conditions were milder than for homemade preparations, the extract obtained was enriched in natural leaf flavonoids. At each step of the pilot plant process, the co-products obtained were analyzed for total polyphenol and total flavonoid contents by the UV-vis spectrophotometric method. The process allowed a better leaf water-extraction of polyphenol compounds than the homemade extraction. The crude extract was concentrated28 times (v/v) at room temperature by membrane volume reduction, and the total content of polyphenolcompounds of the concentrated extract was 17 times higher than those of the crude extract. Individual polyphenol compounds were characterized by HPLC-DAD analysis at [lambda]max= 325 nm. Additional structure characterization was carried out for the two major flavonoid compounds found (65% of total HPLC-DAD peak area of the flavones-type compounds) in the water extracts by tandem mass spectrometry (LC-ESI-MS2) and by nuclear magnetic resonance (1H NMR,13C NMR). They were identified as luteolin 7-O-[ _-glucopyranosyl-(1->2)-béta-rhamnosyl-(1->6)] béta-glucopyranoside and luteolin 7-O-[béta-apiofuranosyl-(1->2)]-béta-xylopyranoside.