Novel process could help provide water-soluble phytosterols

The study, published in Food Chemistry​, outlines a novel method for the production of hydrophilic phytosterol derivatives through a chemo-enzymatic process.

According to the team, the new production method results in phytosterol derivatives with ‘greatly improved’ water solubility – meaning that they have a wide range of potential applications in functional and medical foods.

“Recently, phytosterols have been attracting much interest because of its well-known cholesterol-lowering property,”​ said the team – led by Dr Wen-Sen He from Jiangsu University. “However, the unique chemical structure of phytosterols determines that they are insoluble in water and poorly soluble in oil and fat, which drastically limits their widespread application in food, medical, cosmetic and other industries.”​

While many researchers have focused on the chemical modification of phytosterols with fatty acids to improve fat and oil solubility, “so far, little research has been reported to improve the solubility of phytosterols in water.”​

“In this study, a hydrophilic phytosterol derivatives that did not occur in nature were successfully synthesized by chemo-enzymatic route and the solubility in water was greatly improved,”​ wrote He and his colleagues.

Enzyme process

The team noted that in recent years, the enzymatic synthesis of bioactive compounds and food ingredients has attracted much interest, due to its potential advantages, such as mild reaction conditions and reagents.

Indeed, such methods have already been widely used for the synthesis of phytosteryl fatty acid esters and phenolates, they noted – adding that a previous study reported that phytosteryl oleic acid esters were synthesised catalyzed by Candida rugosa​ lipase in hexane, while other research produced phytosteryl caffeate via a chemo-enzymatic route.

“However, little research has been performed on the synthesis of hydrophilic phytosterol derivatives by lipase-catalyzed synthesis,”​ said the team.

In the new study, however, the team have established a novel chemo-enzymatic preparation of hydrophilic phytosterol derivatives including phytosteryl polyethylene glycol succinate (PPGS).

“In this work, a novel hydrophilic phytosterol derivative PPGS was successfully synthesized by a two-step sequence of chemical acylation of phytosterols with succinic anhydride followed by lipase-catalyzed esterification of PEG 1000 with PSHS ​[phytosteryl hemisuccinate],”​ wrote He and his colleagues.

According to the study, the solubility of PPGS could reach above 28.7 g/100 mL, indicating that 28.7 g PPGS could be dissolved in 100 mL water at 30 °C by coupling with PEG 1000.

“By calculation, the actual solubility of phytosterols was 7.9 g/100 mL water, indicating that 7.9 g phytosterols could be dissolved in 100 mL water at 30 °C by coupling with PEG 1000,”​ the Chinese team wrote.

“The solubility of phytosterols in water was significantly improved by coupling with PEG, facilitating the incorporation into a variety of foods containing water,”​ they concluded.

Source: Food Chemistry​
Volume 192, 1 February 2016, Pages 557–565, doi: 10.1016/j.foodchem.2015.07.047​​
"A novel chemo-enzymatic synthesis of hydrophilic phytosterol derivatives"​
Authors: Wen-Sen He, et al​