The Synthesis Of Phytosteryl Aromatic Organic Acid Esters And Their Functional Properties

Plant sterols have many important physiological properties, such as lowering total cholesterols,antioxidant capacity, anti-inflammatory and so on. Their insolubility in water and poor solubility inoil limits their use in food industry. The paper focused on the synthesis of phytosteryl aromaticorganic acid esters to improve their solubility in oil via chemical reaction. Basic physical charactersof the phytosteryl esters were investigated.[HSO3-bmim][HSO4], which is ionic liquid of sulfonic acid imidazole, catalyzed the synthesisof phytosteryl cinnamate and phytosteryl nicotinate as a reused catalyst. The optimal conditions ofthe synthesis of phytosteryl cinnamate were9%[HSO3-bmim][HSO4] load (w/w),2:1molar ratioacid to sterols,130oC for5h, in which the91.0%of phytosteryl cinnamate were obtained. Thesynthesis of phytosteryl nicotinate was investigated using [HSO3-bmim][HSO4]. The highesterification (72.2%) was obtained under the optimal conditions: dose of [HSO3-bmim][HSO4]80%of phytosterols, the molar ratio of nicotinic acid to plant sterols1.5:1, reaction temperature160oC, reaction time3h.An efficient and reused catalyst, scandium triflate, was used to catalyze the esterificationreaction of plant sterols and ferulic acid, which was screened among the Lewis acid salts. Thehighest yield of85.7%was obtaind under the selected conditions:0.5mmol phytosterols,1.4:1molar ratio of ferulic acid to phytosterols,5mol%Sc(OTf)3load,100oC for2h in12mL toluene.The purification of phytosteryl aromatic acid esters by the thin-layer chromatography andcolumn chromatography was investigated. The eluents of column chromatography for cinnamoylphytosterols and nicotinoyl phytosterols were ethyl acetate/petroleum ether (1:6, v/v), the eluentsfor feruloyl phytosterols were ethyl acetate/n-hexane (1:4, v/v). The quantitative analysis ofphytoseryl esters via HPLC was determined, and the mobile phases and mobile velocity forcinnamoyl phytosterols, nicotinoyl phytosterols and feruloyl phytosterols were methanol:n-hexane:isopropanol (8:1:1, v/v/v)0.8mL/min, methanol:n-hexane: isopropanol (88:6:6, v/v/v)1.0mL/min,methanol:isopropanol (9:1, v/v)0.8mL/min, respectively. The purified products were analyzed byfourier transform infrared spectroscopy, mass spectroscopy and nuclear magnetic resonancespectroscopy and confirmed to be the target products.The solubility in oil, thermal stability, melting and crystallization properties, antioxidantcapacity of plant sterols and phytosteryl esters were explored. Phytosteryl esters had highersolubility in soybean oil, higher pyrolysis temperature than plant sterols. Stigmasteryl esters hadlower melting temperature than stigmasterol, apart from cinnamoyl ester, nicotinoyl ester andferuloyl ester had lower crytallization temperature than stigmasterol. The scavenge capacity ofphytosterols and phytosteryl esters was studied. It was indicated that they could scavenge the freeradicals of DPPH·,·OH and O2-·to some extent, especially feruloyl phytosterols which had astronger capacity than BHT (butylated hydroxytoluene). Cinnamoyl phytosterols and nicotinoylphytosterols had a stronger capacity of scavenging·OH and a weaker capacity of scavengingDPPH·and O2-·than phytosterols.