Enzymatic synthesis of hydrophilic phytosterol polyol esters and assessment of their bioaccessibility and uptake using an in vitro digestion/Caco-2 cell model.

ABSTRACT

A novel enzyme-catalyzed method was developed for the synthesis of phytosterol polyol esters from ß-sitosterol and polyols (sorbitol, mannitol and xylitol) by two-step transesterification using divinyl adipate (DVA) as a link. A high conversion (exceeding 94%) of ß-sitosterol with a vinyl group was achieved, in the presence of Candida rugosa lipase (CRL), at low temperature (35 °C) within 30 min. Subsequently, the maximum conversion of phytosterol polyol esters (>94%) was obtained using alkaline protease from Bacillus subtilis at 65 °C. Phytosterol polyol esters had enhanced thermal stability (up to an above 355 °C) and excellent water solubility (4.6-7.9 mM at 35 °C). Moreover, obvious increases in the bioaccessibility (41.5-63.6%) and intestinal uptake (5.2-6.5%) were observed using a simulated gastrointestinal digestion/Caco-2 cell model. These results highlighted the key role of hydrophilic structural modifications on physicochemical properties and absorption of phytosterols.