Impact of high-pressure extraction techniques on the quality of extracts obtained from local plants

Abstract

In the present work, a multi-analytical approach was proposed to valorise two underused local Algerian plants from arid and non-arid zones, namely Ammodaucus Leucotrichus seeds and Silybum marianum seeds, and study their therapeutic performances. The first part was dedicated to the extraction of oils from the two plant using green processes based on the application of compressed fluids, such as pressurised liquid extraction (PLE), gas-expanded liquid extraction (GXLE) and supercritical fluid extraction (SFE), followed by the identification of the different constituents of the extracts by gas chromatography and liquid chromatography coupled with mass spectrometry. The second part of this thesis was reserved for the study of the neuroprotective activity of the different extracts, through acetylcholinesterase (AChE) and lipoxygenase (LOX) inhibition tests and the antioxidant activity, through free radical scavenging tests (DPPH and ABTS).

PLE using overheated liquid water at 180 °C proved to be a very effective extraction method for obtaining Ammodaucus leucotrichus extract with remarkable neuroprotective activity (IC50 (AChE) = 55, 6 μg/mL, IC50 (LOX)= 39.4 μg/mL and IC50 (DPPH)= 58.51 μg/mL). UHPLC-Q-TOF-MS/MS analysis allowed the preliminary identification of 94 compounds, mainly free and glycosylated phenols, lipids and organic acids. Furthermore, the extracts obtained by the ESF technique, optimized by the Box-Behnken design, showed a high carbohydrate content with low AChE inhibition. In addition, the extracts obtained by sequential PLE-SFE extractions possess relevant antioxidant activity compared to that of the extracts obtained by separate extraction processes. The results of the GC-MS analysis revealed the presence of 32 metabolites, 14 of which were reported for the first time in Ammodaucus leucotrichus. Concerning the seeds of Silybum marianum, the GXLE technique allowed the simultaneous extraction of the five favonolignans composing silymarin with predominance of silybin A + B (545.73 mg of silymarin/g of extract). Furthermore, the extract showed relevant antioxidant and anti-inflammatory potential with IC50 values equal to 8.80 μg/mL and 28.52 μg/mL, respectively, but a moderate AChE inhibition capacity (IC50 = 125.09 μg/mL).