ACTIVITY 3

The method described in the literature for extraction of secondary metabolites from plant matrices includes solid-liquid extraction followed by clean up and concentration of extracts by solid-phase extraction (SPE) using CNWBOND Carbon-GCB SPE Cartridges. Dispersive liquid-liquid microextraction (DLLME) is a novel sample preparation technique based on a ternary component mixture consisting of an aqueous sample, a dispersive solvent and an extraction solvent.

A two-level (2k) factorial design will be applied for identifying the main parameters affecting the extraction procedure, the most significant ones being further optimised by Central Composite Design. LC-electrospray ionization tandem mass spectrometry (LC-ESI/MS/MS) will be applied in the profiling of secondary metabolites within the extracts. Some of the separated compounds will be structurally characterized by vibrational spectroscopy (FTIR and Raman), at QFM-UC, aiming at a more thorough quantitative analysis of the most promising extracts;

Essential oils (OEs) will be prepared from different plant organs according to the respective species. Classical methods of obtaining essential oils – e.g. hydrodistillation, steam distillation accelerated by microwave, will be used as reference.

In order to evaluate the extraction efficiency for each plant and determine the overall composition, chemistry analysis will be achieved by gas chromatography coupled to mass spectrometry (GC/MS) which is the technique usually used to characterize the composition of the essential oils, HPLC techniques and FTIR and Raman that showing analytical advantages such as speed, cost, minimal or non-sample preparation and versatility;

The most promising EOs or aqueous extracts will be included in selected cyclodextrins and the inclusion compounds will be characterized by Raman and tested for stability by chemical evaluation of key odorants and antioxidant capacity, as well as sensory analysis. Thermal stability will also be assayed by thermal scanning microcalorimetry.

The release process of the guest molecule from the supramolecular structure, which is required to be controlled and stimuli-dependent, will be studied by solid-phase microextraction (SPME-GC/MS).

The production and nanoencapsulation of essential oils will be performed in ESAC/IPC and the consequent analysis at REQUIMTE and QFM-UC.