Effect of freeze-drying and spray-drying on total phenolics content and antioxidant activity from aqueous extract of Justicia secunda leaves

This study aims to evaluate the effect of freezedrying and spraydrying on total phenolics con­tents and antioxidant capacity from aqueous extract of Justicia secunda leaves. Total pheno­lic compounds extraction procedure consists of using an extractionconcentration procedure performed at threestep process, including ultrasoundassisted water extraction followed by crossflow microfiltration of the crude extract and its concentration by reverse osmosis. After final step of extraction procedure, a concentrated extract, namely RO extract was obtained. In order to convert RO extract to powder form, two drying methods are used; freezedrying and spraydrying. The powder obtained by freeze drying, namely P1, presented the higher content of polyphenols (9542 ± 38 μmol.g1 GAE) and antioxidant capacity (4256 ± 15 μmol.g^-1 TE) than that obtained by spray drying and namely P2. The freezedrying technology could be a good outcome to preserve polyphenols structure and consequently their antioxidant capacity in aqueous extract of J. secunda leaves. Moreover, seven minor phenolic compounds of RO extract were characterized by HPLC coupled to UV/Vis diode array detection and mass spectrometry with electrospray ionization (LC/DAD/ESIMS). There were kaempferol3Ocoumaroyl gluco­side (10), justiflorinol (14), luteolin7Orutinoside (18), apigenin 6Cglucoside7Orhamno­sylhexoside (19), quercetin7Oglucoside3Orutinoside (20), apigenin7Oneohesperido­side (23), and naringenin7Orutinoside (25) among the characterized compounds.