Quercus cerris extracts obtained by distinct separation methods and solvents: Total and friedelin extraction yields, and chemical similarity analysis by multidimensional scaling

Abstract

This work encompasses a comparison of the extraction of Quercus cerris cork with methanol, ethanol, dichloromethane, and petroleum ether by Soxhlet and room temperature batch solid-liquid extraction (SLE) and with supercritical carbon dioxide modified with ethanol. The maximum total extraction yield (ηTotal) was attained by Soxhlet extraction with methanol (ηTotal = 13.8 wt.%) and the minimum for batch SLE with petroleum ether (ηTotal = 0.35 wt.%). For the supercritical fluid extraction (SFE) runs ηTotal ranged from 1.2 to 1.7 wt.%. In terms of friedelin extraction yields (ηFriedelin) the results ranged from 0.12 wt.% (batch SLE with petroleum ether) to 1.68 wt.% (Soxhlet with methanol). The best performing assays in terms of friedelin concentration in the extracts (CFriedelin) were those involving weakly polar or nonpolar solvents. Batch extractions at room temperature reached CFriedelin values significantly lower than Soxhlet extractions with the same solvent due to the unfavourable effect of temperature on the solubilisation of friedelin. The extracts were analysed by FTIR-ATR and GC–MS and the data used for similarity analysis using multidimensional scaling (MDS). The results unveil that more than the extraction method (Soxhlet, Batch, or SFE) it is the intrinsic polarity of the solvent that defines the ensuing chemical composition of the extracts. For this reason, this study contributes for the selection of solvents and extraction methods of future industrial applications targeting Q. cerris cork valorization.