In vitro release of grape-seed polyphenols encapsulated from uncoated and chitosan-coated liposomes

Abstract

Grape-seed extract (GSE), a rich source for polyphenols, was incorporated into liposomes (1.1% w/w soy lecithin) using high-pressure homogenization (22,500psi). A chitosan coating (1% w/w) was used to obtain more stable liposomes. Physiochemical properties (ζ-potential, mean particle size) of all liposomes were analyzed. In vitro release of GSE-polyphenols from various liposomes was investigated by measuring the total phenolic content of the dialysate (acetate buffer, pH3.8±0.1, 25mM) over time. Diverse kinetic models were used to describe the release of the polyphenols incorporated from liposomes. Z-average particle diameters increased with the incorporation of GSE and chitosan coating. Chitosan-coated liposomes containing GSE had larger particle sizes than coated liposomes without GSE. The ζ-potential changed from -38mV in uncoated liposomes to +65mV in coated liposomes. Entrapment efficiency for uncoated and coated liposomes was 88.2±4.7% and 99.5±2.3%, respectively. The release rate increased gradually by increasing time. In vitro release of GSE polyphenols from both uncoated and coated liposomes followed an exponential equation (first order Q(t)=a·(1-exp(-k·t))). The release from coated liposomes was much lower than uncoated liposomes. The release rate after 24h from uncoated liposomes was 0.55 and from coated liposomes was 0.24. This study indicates that the release of bioactive compounds from liposomes can be reduced by coating with chitosan, allowing an application of coated liposomes with a controlled release of GSE polyphenols in water-based foods.

Keywords: Chitosan; Encapsulation; Grape-seed extract; Liposomes; Polyphenols; Release; Release models.