Triphenylphosphine oxide (TPPO) and oxalyl chloride ((COCl)2) are used as novel and high-efficiency coupling reagents for the esterification of alcohols with carboxylic acids via the TPPO/(COCl)2 system at room temperature for 1 h. The reaction represents the first TPPO-promoted esterification under mild and neutral conditions with excellent yields. Furthermore, we proposed a plausible mechanis...

In recent times, biotechnological applications of microbial lipases in synthesis of many organic molecules have rapidly increased in non-aqueous media. Microbial lipases are the 'working horses' in biocatalysis and have been extensively studied when their exceptionally high stability in non-aqueous media has been discovered. Stability of lipases in organic solvents makes them commercially feasi...

Isolated soil humic acid (HA) and commercial Aldrich HA were derivatized by esterification with methanol-thionyl and acetylation with acetic anhidride, in order to obtain derivatives with selectively blocked carboxyl and phenol groups, respectively. Results obtained by FT-IR spectroscopy and potentiometry show that the methanol-thionyl procedure is a selective, specific and efficient route for ...

A microsomal fraction from flax hypocotyls (Linum usitatissimum L) showed a methylation ability from S-adenosyl-methionine on to the cell wall polysaccharides. Two kinds of methylation were found: (i) a methyl esterification of uronic acids in the oxalate extracts and (ii) an O-methylation of the hydroxyl groups in the NaOH extracts. The methyltransferase study showed a rapid decrease of the me...

Glucose fatty acid esters can be served as a low calories fat replacer and emulsifier. The study aims to synthesize esters enzymatically catalyzed by immobilized lipase on the activated natural zeolite. Optimal immobilization carried out at temperatures of 37°C, with a ratio of enzyme: zeolite = 1: 3 (w / w) gave 74.81 % loading efficiency. Immobilization occurs on the surface of the zeolite ar...

An alternative route to produce biodiesel is based on esterification of free fatty acids present in byproducts obtained from vegetable oil refining, such as palm oil fatty acid distillate (PFAD). PFAD is a byproduct of the production of edible palm oil, which contains 96 wt.% of free fatty acids. The purpose of this work was to study biodiesel synthesis via esterification of PFAD with methanol ...

Yeast Saccharomyces cerevisiae is auxotrophic for ergosterol in the absence of oxygen. We showed that complex changes in esterification of exogenously supplied sterols were also induced by anaerobiosis. Utilization of oleic acid for sterol esterification was significantly impaired in anaerobic cells. Furthermore, anaerobic cells fed different sterols exhibited striking variation in esterificati...

Production of fatty acid esters from stearic, oleic, and palmitic acids and short-chain alcohols (methanol, ethanol, propanol, and butanol) for the production of biodiesel was investigated in this work. A series of montmorillonite-based clays catalysts (KSF, KSF/0, KP10, and K10) were used as acidic catalysts. The influence of the specific surface area and the acidity of the catalysts on the es...

Soluble amyloid-β (Aβ) oligomers, a key driver of pathogenesis in Alzheimer disease, bind to cellular prion proteins (PrPC) expressed on synaptosomes resulting in increased cholesterol concentrations, movement of cytoplasmic phospholipase A2 (cPLA2) to lipid rafts and activation of cPLA2. The formation of Aβ-PrPC-cPLA2 complexes was controlled by the cholesterol ester cycle. Thus, Aβ activated ...