Chain separation of monounsaturated fatty acid methyl esters by argentation thin-layer chromatography

Silver-mediated separations: A comprehensive review on advancements of argentation chromatography, facilitated transport membranes, and solid-phase extraction techniques and their applications

The use of silver(I) ions in chemical separations, also known as argentation separations, is a powerful approach for the selective separation and analysis of many natural and synthetic organic compounds. In this review, a comprehensive discussion of the most common argentation separation techniques, including argentation-liquid chromatography (Ag-LC), argentation-gas chromatography (Ag-GC), argentation-facilitated transport membranes (Ag-FTMs), and argentation-solid phase extraction (Ag-SPE) is provided. For each of these techniques, notable advancements, optimized separations, and innovative applications are discussed. The review begins with an explanation of the fundamental chemistry underlying argentation separations, mainly the reversible π-complexation between silver(I) ions and carbon-carbon double bonds. Within Ag-LC, the use of silver(I) ions in thin-layer chromatography, high-performance liquid chromatography, as well as preparative LC are explored. This discussion focuses on how silver(I) ions are employed in the stationary and mobile phase to separate unsaturated compounds. For Ag-GC and Ag-FTMs, different silver compounds and supporting media are discussed, often with relation to olefin-paraffin separations. Ag-SPE has been widely employed for the selective extraction of unsaturated compounds from complex matrices in sample preparation. This comprehensive review of Ag-LC, Ag-GC, Ag-FTMs, and Ag-SPE techniques emphasizes the immense potential of argentation separations in separations science and serves as a valuable resource for researchers seeking to learn, optimize, and utilize argentation separations.

A convenient route to mono-trans polyunsaturated free fatty acids

Trans unsaturated fatty acids in humans may be originated both from dietary supplementation and from an endogenous free-radical-catalyzed cis−trans isomerization of fatty acid residues in naturally occurring cis lipids. The latter process affords geometrical isomers and the polyunsaturated fatty acid mono-trans isomers were demonstrated to be connected with stress conditions in living organisms. Synthesis of mono-trans polyunsaturated fatty acid is useful for analytical and biological research, and in this case, the availability of free fatty acids is needed as well as the possibility of mg scale of the synthetic protocol. Herein, we report a simple synthetic route to mono-trans isomers of arachidonic acid, eicosapentaenoic acid, and docosahexaenoic acid, which includes thiyl radical-catalyzed isomerization reaction of polyunsaturated fatty acid methyl esters and fraction isolation of mono-trans mixture isomers followed by optimization of hydrolysis condition to free fatty acids and purification of each mono-trans polyunsaturated fatty acid. Our approach to mono-trans polyunsaturated fatty acids as free acids can reach the mg scale, thus fostering more applications to biochemical and biological studies.

Traditional Chinese medicine prescription Guizhi Fuling Pills in the treatment of endometriosis

Endometriosis (EMs) is recorded as Zheng Jia in traditional Chinese medicine (TCM) books. Guizhi Fuling Pills (GFPs), a classic prescription for promoting blood circulation and removing blood stasis, is widely used for women's blood stasis diseases represented by Zheng Jia. At present, it has been applied to treat EMs in clinical settings. In this review, we systematically summarized the active ingredients and pharmacological mechanism of five Chinese herbs contained in GFPs and clinical applications of GFPs. The potential pathways of GFPs in the treatment of EMs were explored through network pharmacology. The current researches results indicate that the mechanisms of GFPs in the treatment of EMs mainly include acesodyne, anti-inflammation and improvement of hemodynamics. The main active compounds that are responsible for pharmacological effects in five Chinese herbs are paeonol, pachymic acid, cinnamaldehyde, amygdaloside and Paeoniflorin. This review can lay the foundation and identify the research direction for the development of GFPs as a new drug therapy for the treatment of EMs.

Combined urea-thin layer chromatography and silver nitrate-thin layer chromatography for micro separation and determination of hard-to-detect branched chain fatty acids in natural lipids

A simple, fast and efficient procedure was developed for micro separation and enrichment of branched chain fatty acids (BCFA) from natural products using successive thin layer chromatography (TLC) technique coupling novel urea-TLC with AgNO3-TLC, which rely on the formation of urea adduction and AgNO3 bonding in methanol. These natural lipids contain a significant amount of straight chain fatty acids (FA). Fresh and fast urea-TLC and AgNO3-TLC plate making techniques were developed with more even coating and less coating material contamination before being utilized for separation. Goat milk fat was used as a model. Various experimental parameters that affect urea-TLC and AgNO3-TLC separation of BCFA were investigated and optimized, including coating of urea, concentration of original oil sample, mobile phase and sample application format. High efficiency of removal of straight chain FA was achieved with a low amount of sample in an easy and fast way. A total BCFA mix with much higher purity than previous studies was successfully achieved. The developed method has also been applied for the concentration and analysis of BCFA in cow milk fat and Anchovy oil.

Chromatographic Methods in the Separation of Long-Chain Mono- and Polyunsaturated Fatty Acids

This review presents various chromatographic systems, TLC, HPLC, GC, and also SFC, developed for identification and accurate quantification of long-chain mono- and polyunsaturated fatty acids from different samples with emphasis on selected literature which was published during last decade. Almost all the aspects such as preseparation step of fatty acids (cisandtrans), stationary phase, solvent system, and detection mode are discussed.

The role of membrane fatty acid remodeling in the antitumor mechanism of action of 2-hydroxyoleic acid

The synthetic fatty acid 2-hydroxyoleic acid (2OHOA) is a potent antitumor drug that we rationally designed to regulate the membrane lipid composition and structure. The lipid modifications caused by 2OHOA treatments induce important signaling changes that end up with cell death (Terés et al., 2012 [1]). One of these regulatory effects is restoration of sphingomyelin levels, which are markedly lower in cancer cells compared to normal cells (Barceló-Coblijn et al., 2011 [2]). In this study, we report another important regulatory effect of 2OHOA on cancer cell membrane composition: a large increase in 2OHOA levels, accounting for ~15% of the fatty acids present in membrane phospholipids, in human glioma (SF767 and U118) and lung cancer (A549) cells. Concomitantly, we observed marked reductions in oleic acid levels and inhibition of stearoyl-CoA desaturase. The impact of these changes on the biophysical properties of the lipid bilayer was evaluated in liposomes reconstituted from cancer cell membrane lipid extracts. Thus, 2OHOA increased the packing of ordered domains and decreased the global order of the membrane. The present results further support and extend the knowledge about the mechanism of action for 2OHOA, based on the regulation of the membrane lipid composition and structure and subsequent modulation of membrane protein-associated signaling.

Genistein downregulates de novo lipid synthesis and impairs cell proliferation in human lung cancer cells

Cancer cells require high levels of lipid synthesis to produce structural, signaling and energetic lipids to support continuous replication. We and others have reported that constitutively increased lipogenesis, mainly by the tandem activation of acetyl-CoA carboxylase, fatty acid synthase and stearoyl-CoA desaturase-1 (SCD1), is critical to sustain the biological features of cancer cells, making this metabolic pathway a potential anticancer target for nutritional and pharmacological interventions. Isoflavones are biologically potent botanical compounds that possess clear antilipogenic and anticancer properties; however, the regulatory effects of these nutraceutical agents on lipid biosynthesis in cancer cells are still not well understood. Here we show that genistein, an isoflavone abundant in soybeans, decreased the levels of SCD1 protein in H460 human lung adenocarcinoma cells, consequently reducing the rate of biosynthesis of oleic acid as well as its presence in cancer cell lipids. Moreover, genistein promoted a marked reduction in de novo synthesis of major phospholipids, triacylglycerol and cholesterolesters. Finally, cancer cells treated with genistein displayed a dramatic reduction in cell proliferation as a result of a blockade in cell cycle progression through G(2)/M phases. As a whole, our data suggest that, by globally downregulating lipid biosynthesis, genistein suppresses cancer cell growth, emphasizing the relevance of this botanical compound as a potential therapeutic agent against lung cancer, a disease for which therapeutic choices remain limited.

Abrogation of de novo lipogenesis by stearoyl-CoA desaturase 1 inhibition interferes with oncogenic signaling and blocks prostate cancer progression in mice

Increased de novo fatty acid (FA) synthesis is one hallmark of tumor cells, including prostate cancer. We present here our most recent results showing that lipid composition in human prostate cancer is characterized by an increased ratio of monounsaturated FA to saturated FA, compared with normal prostate, and evidence the overexpression of the lipogenic enzyme stearoyl-CoA desaturase 1 (SCD1) in human prostate cancer. As a new therapeutic strategy, we show that pharmacologic inhibition of SCD1 activity impairs lipid synthesis and results in decreased proliferation of both androgen-sensitive and androgen-resistant prostate cancer cells, abrogates the growth of prostate tumor xenografts in nude mice, and confers therapeutic benefit on animal survival. We show that these changes in lipid synthesis are translated into the inhibition of the AKT pathway and that the decrease in concentration of phosphatidylinositol-3,4,5-trisphosphate might at least partially mediate this effect. Inhibition of SCD1 also promotes the activation of AMP-activated kinase and glycogen synthase kinase 3alpha/beta, the latter on being consistent with a decrease in beta-catenin activity and mRNA levels of various beta-catenin growth-promoting transcriptional targets. Furthermore, we show that SCD1 activity is required for cell transformation by Ras oncogene. Together, our data support for the first time the concept of targeting the lipogenic enzyme SCD1 as a new promising therapeutic approach to block oncogenesis and prostate cancer progression.

Inhibition of stearoylCoA desaturase-1 inactivates acetyl-CoA carboxylase and impairs proliferation in cancer cells: role of AMPK

Cancer cells activate the biosynthesis of saturated fatty acids (SFA) and monounsaturated fatty acids (MUFA) in order to sustain an increasing demand for phospholipids with appropriate acyl composition during cell replication. We have previously shown that a stable knockdown of stearoyl-CoA desaturase 1 (SCD1), the main Δ9-desaturase that converts SFA into MUFA, in cancer cells decreases the rate of lipogenesis, reduces proliferation and in vitro invasiveness, and dramatically impairs tumor formation and growth. Here we report that pharmacological inhibition of SCD1 with a novel small molecule in cancer cells promoted the activation of AMP-activated kinase (AMPK) and the subsequent reduction of acetylCoA carboxylase activity, with a concomitant inhibition of glucose-mediated lipogenesis. The pharmacological inhibition of AMPK further decreased proliferation of SCD1-depleted cells, whereas AMPK activation restored proliferation to control levels. Addition of supraphysiological concentrations of glucose or pyruvate, the end product of glycolysis, did not reverse the low proliferation rate of SCD1-ablated cancer cells. Our data suggest that cancer cells require active SCD1 to control the rate of glucose-mediated lipogenesis, and that when SCD1 activity is impaired cells downregulate SFA synthesis via AMPK-mediated inactivation of acetyl-CoA carboxylase, thus preventing the harmful effects of SFA accumulation.

Membrane lipidomics and the geometry of unsaturated fatty acids from biomimetic models to biological consequences

In the last decades, free radical processes delineated an interdisciplinary field linking chemistry to biology and medicine. Free radical mechanisms became of importance as molecular basis of physiological and pathological conditions. Lipids, in particular, unsaturated fatty acids, are susceptible of free radical attack. The reactivity of the double bond toward free radicals is well known, in particular the reversible addition of radical species to this functionality determines the cis-trans double bond isomerization. Since the prevalent geometry displayed by unsaturated fatty acids in eukaryotes is cis, the occurrence of the cis-trans isomerization by free radicals corresponds to the loss of an important structural information linked to biological activity. The formation of trans isomers can have important meaning and consequences connected to radical stress. Free radical isomerization of membrane fatty acids has been the subject of research coupling the top-down approach by model studies, such as biomimetic chemistry in liposomes, with the bottom-up approach dealing with the examination of cell membrane lipidome in living systems under several physiopathological conditions. Methodologies and molecular libraries have been settled, for both liposome experiments and the examination of the radical stress in biological membranes. This chapter will give an overview of the current procedures used for liposome models and the cis-trans isomerization experiments, in order to build-up a library of trans geometrical fatty acid isomers.

Stearoyl-CoA Desaturase Is Involved in the Control of Proliferation,Anchorage-independent Growth, and Survival in Human TransformedCells

Saturated and monounsaturated fatty acids are the most abundant fatty acid species in mammalian organisms, and their distribution is regulated by stearoyl-CoA desaturase, the enzyme that converts saturated into monounsaturated fatty acids. A positive correlation between high monounsaturated fatty acid levels and neoplastic transformation has been reported, but little is still known about the regulation of stearoyl-CoA desaturase in cell proliferation and apoptosis, as well as in cancer development. Here we report that simian virus 40-transformed human lung fibroblasts bearing a knockdown of human stearoyl-CoA desaturase by stable antisense cDNA transfection (hSCDas cells) showed a considerable reduction in monounsaturated fatty acids, cholesterol, and phospholipid synthesis, compared with empty vector transfected-simian virus 40 cell line (control cells). hSCDas cells also exhibited high cellular levels of saturated free fatty acids and triacylglycerol. Interestingly, stearoyl-CoA desaturase-depleted cells exhibited a dramatic decrease in proliferation rate and abolition of anchorage-independent growth. Prolonged exposure to exogenous oleic acid did not reverse either the slower proliferation or loss of anchorage-independent growth of hSCDas cells, suggesting that endogenous synthesis of monounsaturated fatty acids is essential for rapid cell replication and invasiveness, two hallmarks of neoplastic transformation. Moreover, apoptosis was increased in hSCDas cells in a ceramide-independent manner. Finally, stearoyl-CoA desaturase-deficient cells were more sensitive to palmitic acid-induced apoptosis compared with control cells. Our data suggest that, by globally regulating lipid metabolism, stearoyl-CoA desaturase activity modulates cell proliferation and survival and emphasize the important role of endogenously synthesized monounsaturated fatty acids in sustaining the neoplastic phenotype of transformed cells.