Modeling and optimization of lipase-catalyzed esterification of policosanols with conjugated linoleic acid by response surface methodology

Abstract

The aim of this study was to model the lipase-catalyzed esterification of policosanols with conjugated linoleic acid (CLA) in a solvent-free system to produce wax esters which had a lower melting point than that of their corresponding policosanol forms and to optimize the reaction conditions by response surface methodology (RSM). Novozym 435 was selected as a suitable biocatalyst for the reaction. The molar ratio of substrates (policosanols to CLA) was 1:2. A well-fitting quadratic polynomial regression model for the degree of esterification (DE) of policosanols with CLA was established with regard to temperature (35–65°C), enzyme loading (1–5% of weight of total substrates), and reaction time (10–50 min). Optimal reaction conditions were 61.3°C for temperature, 3.7% for enzyme loading, and 34.1 min for reaction time, and the DE was ? 95 mol% under these conditions. The policosanols and wax esters synthesized under optimal conditions had melting points of 79°C and 57°C, respectively.     

Re-characterization of three conjugated linolenic acid isomers by GC-MS and NMR

Conjugated linolenic acids (CLN) refer to a group of octadecatrienoic acids with three conjugated double bonds. Minor positional and geometrical differences among CLN isomers make their separation and identification difficult. We have used GC-MS and NMR to study three common CLN isomers namely alpha-eleostearic acid, beta-eleostearic acid and punicic acid, finding that some signals of olefinic carbon atoms in NMR spectra were mistakenly assigned in the literature. The present study was therefore undertaken to re-characterize the location of CC double bonds and assign the chemical signals of proton and carbon atoms using (1)H NMR, (13)C NMR, (1)H-(1)H two-dimensional correlation spectra ((1)H-(1)H COSY) and (13)C-(1)H two-dimensional correlation spectra ((13)C-(1)H COSY). The geometrical structure of double bonds in these three CLN isomers was identified using homonuclear decoupling technique.     

酶法生产共轭亚油酸的研究进展

共轭亚油酸(Conjugated linoleic acid,CLA)具有抗癌、抗动脉粥样硬化、减肥和免疫调节等生理活性。共轭亚油酸可以通过酶法异构化获得,将底物亚油酸异构形成具有生物活性物质-共轭亚油酸的异构酶称为亚油酸异构酶。因此,通过介绍亚油酸异构酶的来源、作用机制、酶学性质和基因工程菌生产等方面的研究进展,结合不断发展的基因工程技术,旨在提高亚油酸异构酶的活性、产量和异构化效率,以扩大反应底物范围,降低生产成本,从而推进共轭亚油酸的规模化、可持续性的工业生产。     

Quercetin metabolites inhibit copper ion-induced lipid peroxidation in rat plasma

The oxidative susceptibility of plasma obtained from rats after intragastric administration of quercetin was studied to know whether or not quercetin acts as an in vivo antioxidant after metabolic conversion. Quercetin was raised in the rat blood plasma essentially as glucuronide and/or sulfate conjugates. The plasma obtained from rats after quercetin administration was more resistant against copper sulfate-induced lipid peroxidation than the control plasma on the basis of the accumulation of cholesteryl ester hydroperoxides and the consumption of α-tocopherol. The results strongly suggest that some conjugated metabolites of quercetin act as effective antioxidants when plasma is subject to metal ion-induced lipid peroxidation.     

Comparison of fatty acid composition of bacterial and protozoal fractions in rumen fluid of sheep fed diet supplemented with sunflower, rapeseed and linseed oils

The objective of this study was to investigate effects of oil supplements on the composition of fatty acids (FA), especially of trans11-C18:1 (vaccenic acid, TVA) and cis9, trans11-C18:2 conjugated linoleic acid (c9,t11-CLA), in bacterial (BF) and protozoal (PF) fractions of rumen fluid of sheep that was fractionated centrifugation. Four sheep were fed a diet consisting of meadow hay (960 g dry matter (DM)/day) and of barley grain (240 g DM/day), with sunflower oil (SO), rapeseed oil (RO) or linseed oil (LO) as supplements (60 g/day) in a Latin square design. The oils were used as they are rich in linoleic acid (SO, 533 g/kg of FA), oleic acid (RO, 605 g/kg of FA) and α-linolenic acid (LO, 504 g/kg of FA). Compared to the control (i.e., without oils), oil supplements influenced the concentration of unsaturated (UFA) and saturated fatty acids (SFA). In both BF and PF, the main fatty acids were palmitic and stearic, but PF contained a higher proportion of TVA and c9,t11-CLA than BF. In PF, TVA concentrations, ranked by oil supplement, were SO > RO > LO > Control (174, 150, 118, 74 g/kg of FA, respectively) and the c9,t11-CLA concentrations were RO > SO > LO > Control (59, 51, 27 and 15 g/kg of FA, respectively). Concentrations of c9,t11-CLA in PF were two to three times higher than in BF with all the oil supplements versus the control. Oil treatments impacted the c9,t11-CLA concentration in the fractions, especially SO and RO. The protozoal fraction contained a higher proportion of TVA and c9,t11-CLA than did the bacterial fraction, and dietary addition of SO, RO and LO resulted in a higher incorporation of TVA into both bacterial and protozoal microbial fractions, which probably positively affected TVA flow from the rumen.     

反刍动物体内共轭亚油酸生物合成途径研究进展

共轭亚油酸是一组共轭双键具有不同位置和几何构象的亚油酸异构体,主要存在于反刍动物的肉及乳中。本文就其中2种具有重要生理功能的共轭亚油酸(c-9,t-11CLA和t-10,c-12CLA)的生物合成途径的研究进行综述,以期了解共轭亚油酸代谢途径及其调控路径,为今后利用合成生物学指导共轭亚油酸的合成奠定基础。     

Methods for determination of lipid peroxidation in biological samples

Interest in the pathological consequences of lipid peroxidation has led to the development of a number of analytical approaches to the quantitation of products. However, the various analytical methodologies employed often do not measure the same chemical classes of products, and apparent discrepencies have been observed, particularly in studies of lipid peroxidation in biological systems. This review provides a brief discussion of some of the strengths and weakness of methods currently used for the determination of lipid peroxidation in biological tissues.     

Almond (Prunus dulcis (Mill.) D.A. Webb) polyphenols: From chemical characterization to targeted analysis of phenolic metabolites in humans

In this paper, a survey of our studies on almond polyphenols including their chemical characterization and further bioavailability in humans is reported. Combination of analytical techniques (LC-DAD/fluorescence, LC/ESI-MS and MALDI-TOF-MS) allowed us, for the first time, the identification of A- and B-type procyanidin, propelargonidin and prodelphinidin polymers in almond skins. Glucuronide, O-methyl glucuronide, sulfate and O-methyl sulfate derivatives of (epi)catechin, as well as the glucuronide conjugates of naringenin and isorhamnetin, and sulfate conjugates of isorhamnetin, together with conjugates of hydroxyphenylvalerolactones were detected in plasma and urine samples after the intake of almond skin polyphenols. In addition, numerous microbial-derived metabolites, including hydroxyphenylpropionic, hydroxyphenylacetic, hydroxycinnamic, hydroxybenzoic and hydroxyhippuric acids were also identified. Depending of the type of metabolite, maximum urinary excretion was attained at different time in comparison to the control group in the course of the 24-h period of urine excretion, allowing us to establish the onset of microbial metabolism.     

Synthesis,copolymerization and peptide-modification of carboxylic acid-functionalized 3,4-ethylenedioxythiophene (EDOTacid) for neural electrode interfaces

Background

Conjugated polymers have been developed as effective materials for interfacing prosthetic device electrodes with neural tissue. Recent focus has been on the development of conjugated polymers that contain biological components in order to improve the tissue response upon implantation of these electrodes.

Methods

Carboxylic acid-functionalized 3,4-ethylenedioxythiophene (EDOTacid) monomer was synthesized in order to covalently bind peptides to the surface of conjugated polymer films. EDOTacid was copolymerized with EDOT monomer to form stable, electrically conductive copolymer films referred to as PEDOT-PEDOTacid. The peptide GGGGRGDS was bound to PEDOT-PEDOTacid to create peptide functionalized PEDOT films.

Results

The PEDOT-PEDOTacid-peptide films increased the adhesion of primary rat motor neurons between 3 and 9 times higher than controls, thus demonstrating that the peptide maintained its biological activity.

Conclusions

The EDOT-acid monomer can be used to create functionalized PEDOT-PEDOTacid copolymer films that can have controlled bioactivity.

General Significance

PEDOT-PEDOTacid-peptide films have the potential to control the behavior of neurons and vastly improve the performance of implanted electrodes. This article is part of a Special Issue entitled Organic Bioelectronics—Novel Applications in Biomedicine.