HPLC determination of phenolics adsorbed on yeasts.

An analytical HPLC method was developed to determine monomeric anthocyans as catechin (CA), flavonols as rutin (RU) and phenol acids as gallic acid (GA) adsorbed on the cell wall of 23 Saccharomyces cerevisiae strains grown on two media containing high levels of phenolic compounds, from grape seeds and grape skins, and on one control medium. Microbial biomass purification by liquid-liquid extraction of the phenolics is followed by reversed-phase chromatographic separation and CA, RU and GA detection by ultraviolet detector. The method was linear over the studied range of concentrations: GA at 0.12-0.96 microg/ml, CA at 0.25-20.00 microg/ml and RU at 0.02-0.20 microg/ml. The correlation coefficient for each analyte was greater than 0.9983. The recovery was greater than 85% for both GA and RU, and greater than 94% for CA. The detection limits for GA, CA and RU were determined to be 0.015, 0.025 and 0.029 microg/mg of biomass, respectively. The proposed method is highly responsive for the determination of different phenolics, and seems to be useful to evaluate their adsorption profile on yeasts.