Supercritical Antisolvent Fractionation of Antioxidant Compounds from Salvia officinalis

Abstract

The increasing interest towards greener antioxidants obtained via natural sources and more sustainable processes encourages the development of new theoretical and experimental methods in the field of those compounds. Two advanced separation methods using supercritical CO2 are applied to obtain valuable antioxidants from Salvia officinalis, and a first approximation to a QSAR model relating molecular structure with antioxidant activity is explored in order to be used, in the future, as a guide for the preselection of compounds of interest in these processes. Separation experiments through antisolvent fractionation with supercritical CO2 were designed using a Response Surface Methodology to study the effect of pressure and CO2 flow rate on both mass yields and capability to obtain fractions enriched in three antioxidant compounds: chlorogenic acid, caffeic acid and rosmarinic acid which were tracked using HPLC PDA. Rosmarinic acid was completely retained in the precipitation vessel while chlorogenic and caffeic acids, though distributed between the two separated fractions, had a major presence in the precipitation vessel too. The conditions predicted for an optimal overall yield and enrichment were 148 bar and 10 g/min. Although a training dataset including much more compounds than those now considered can be recommended, descriptors calculated from the σ-profiles provided by COSMO-RS model seem to be adequate for estimating the antioxidant activity of pure compounds through QSAR.

Concentration of Antioxidant Compounds from Calendula officinalis through Sustainable Supercritical Technologies, and Computational Study of Their Permeability in Skin for Cosmetic Use

“…The pre-treated material, previously ground and sieved, was defatted in a first stage to facilitate the obtaining of the antioxidant fraction. This stage was usually carried out by means of maceration in hexane [ 41 , 45 ], but in a more recent study, supercritical extraction with CO 2 was used [ 51 ]. This is due to the advantages offered by this type of extraction; since it is a non-toxic solvent, its polarity facilitates the extraction of lipophilic compounds and generates solvent-free final products because it can be easily removed by lowering the pressure.…”

“…In a first stage, the plant material was defatted with supercritical CO 2 in a Waters laboratory scale plant (SFE-1000F-2-FMC10 System, Pennsylvania, USA). Its scheme has been published previously [ 51 ] and its main components consist of an extraction vessel of 1 L (E), and two 0.5 L collectors (C1, C2). All three vessels were jacketed to maintain a constant temperature.…”

“…The procedure is the same as that performed in previous works [ 51 ]. The same proportion of plant material/inert glass bead was used (100 g/200 g), which allows a better CO 2 –solid contact, and therefore facilitates better extraction.…”

“…The flow rate applied was 0.8 mL/min. For each sample 100 ppm was prepared in SAF fractions (FS, PV and DV) and filtered through a 0.2 μm filter ( GH Polypropylene membrane ACRODISC 13 mm, Waters ® , MA, USA) [ 51 ]. CHA, CAF and FA standards were used to build the calibrations curves, and the conditions for analysing them were the same.…”

“…The values were set between 80 and 160 for pressure in PV, X P , and 10–60 g/min for CO 2 flow rate, XQ CO 2 . The rest of the parameters in the experiments—temperature in PV and DV, pressure in DV, and FS flow rate—were constant and were set according to previous experience to ensure the supercritical conditions of the CO 2 –ethanol mixture [ 51 ].…”