| Abstract [eng] |
A matrix solid-phase dispersion (MSPD) extraction method was applied for flavonols in cranberries for the first time. Three flavonols myricetin, quercetin and kaempferol were determined by HPLC-DAD-MS. Results based on the tests provided optimal conditions for MSPD extraction of flavonols from cranberries were: 0.25 g of the freeze-dried cranberry sample, 1.0 g of C18 as dispersant sorbent and 10 mL of methanol and its aqueous solutions as the eluting solvents. The LOD varied from 0.04 µg/g to 0.08 µg/g with linear regression coefficients (r2 >0.998) for each compound in optimized conditions. The main advantage of this method is much less time consuming sample preparation procedure accompanied by much smaller quantities of solvents. The quercetin (QU) has been successfully entrapped into lipid-based liquid crystalline systems. The lipid mixtures composed of mono- and di-glycerides have very limited ability to solubilize QU. In contrast, quercetin solubility in SPC/GDO-based formulations is in the order of magnitude higher and is about 4-5 wt%. The effect of QU on the nanostructure of LC phases is lipid composition dependent. At high SPC content, the entrapment of QU has practically no effect on the nanostructure of H2 phase. Contrary to H2 phase, the structure of Fd3 ̅m cubic phase prepared at low SPC content is rather sensitive to QU entrapment and temperature. Finally, concentrated and colloidally stable non-lamellar SPC/GDO-based LCNP dispersions containing up to 2 wt% of entrapped QU can be easily prepared in the presence of stabilizer P80. The chemical stability of quercetin in three different systems ranked in the following order:lipid LC formulations > lipid LC phases > LCNP dispersions. Different lipid SPC/GDO-based delivery systems with entrapped quercetin and natural cranberries flavonoids retain antioxidant properties even after 30 days of storage, whereas the antioxidant properties of natural cranberries extract are decreasing over time. |
