Static−Dynamic Superheated Liquid Extraction of Hydroxytyrosol and Other Biophenols from Alperujo (a Semisolid Residue of the Olive Oil Industry)

Hydroxytyrosol and other olive biophenols (OBPs) such as tyrosol, verbascoside, apigenin-7-glucoside, and α-taxifolin have been extracted from alperujo by using static−dynamic superheated liquids. Multivariate methodology has been used to carry out a detailed optimization of the extraction. Under the optimal working conditions no further extraction of the target analytes was achieved after 27 min (up to 2800 and 1500 mg/kg of hydroxytyrosol and tyrosol, respectively), so complete removal of them within this interval was assumed. The extract was injected into a chromatograph−photodiode array detector assembly for individual separation−quantification. The efficacy of ethanol/water mixtures to extract OBPs from alperujo has been demonstrated and compared with that of a conventional stirring-based method. These less toxic extractant mixtures are of interest with a view to future human uses of OBPs. Keywords: Alperujo; olive waste; olive wastewater; hydroxytyrosol; tyrosol; verbascoside; phenols; biophenols; OBPs; superheated liquid extraction