Optimisation of Polyphenols Extraction from Wild Bilberry Leaves-Antimicrobial Properties and Stability Studies.

Polyphenolic extracts from natural sources have received great interest due to their beneficial properties for human health. A method to reduce their variability is to use the design of experiments which allows a limited number of experiments to be performed while exploring the experimental space. Firstly, a 23-full factorial model was used to investigate the polyphenols extraction from wild bilberry leaves. Spectrophotometric data (the content of polyphenols, flavonoids, chlorophyll and radical scavenger activity) and extraction yield were used as responses, and six statistical models were determined depending on the two numerical factors (temperature and alcohol % of ethanol-water mixture) being significant (p < 0.05) in all cases. Numerical optimisation performed by Design Expert 13 software correlates well with the chemical profile determined by high-performance liquid chromatography and the amount of the polyphenol. Afterwards, under the optimised conditions, an extract was prepared in three extraction steps for which composition, chemical stability and antimicrobial properties were evaluated. The antimicrobial potential of the extract was compared with that of the standard compounds (rutin and chlorogenic acid), and the results supported a synergistic effect of the extract components.

Polyphenols extract from grape pomace. Characterization and valorisation through encapsulation into mesoporous silica-type matrices.

We report the encapsulation of two grape pomace polyphenolic extracts into mesoporous MCM-41-type silica matrices (pristine and Zn or Mg heteroatom modified) to reduce the extract sensitivity and enhance its stability, while preserving the radical scavenger activity. Various grapes marc (Cabernet Saugvinon and Feteasca Neagra from the Black Sea region and commercially available grape skins powder) were used to prepare ethanolic extracts either through conventional extraction, or microwave-assisted procedure. The polyphenolic extracts composition was analysed by reversed phase-high pressure liquid chromatography and spectrometric determination of total polyphenols and ascorbic acid (using Folin Ciocalteu reagent), total flavonoids (by AlCl3 complexation), as well as total anthocyanin monomeric pigments content. The encapsulated extract into MCM-41 silica, as well as Zn-MCM-41 and Mg-MCM-41 matrices showed an enhanced radical scavenger activity assessed by DPPH procedure developed for solid samples. The cytocompatibility tests performed on HaCaT keratinocyte human cells demonstrated a good cytocompatibility for the Cabernet Saugvinon and grape skins extracts free and encapsulated into MCM-41-type matrices.