New ceramides from the flower of Albizia iulibrissin

A new ceramide and its glycoside were isolated from the flower of Albizia julibrissin. Their structures were established as (25,35,4R,8E)-2-[(2'R)-hydroxyhexadecanoylamino]-8-tetra-cosene-l,3,4-triol(I)and 1-O-β-D-glucopyranosy1-(2S,3S,4R,8E)-2-[(2'R)-hydroxy-hexade-canoylamino]-8-tetracosene-1,3,4-triol (II) on the basis of chemical and spectroscopic studies.     

Synthesis and anti-tumor activity of β-C-glycoside analogs of the immunostimulant KRN7000

A ring-closing metathesis approach was employed for the synthesis of a β-C-glycoside analog of the immunostimulant KRN7000. The protected C-glycosyl amino acid derivative 18 was converted to amino-olefin 20, and osmylation served to install the diol unit as a mixture of separable syn and anti isomers. Deprotection to the hydroxy-amine 21 was followed by N-acylation and debenzylation to deliver the target compound 5.     

New ceramides from the flower of Albizia julibrissin

A new ceramide and its glycoside were isolated from the flower of Albizia julibrissin. Their structures were established as(2S,3S,4R,8E)-2-[(2'R)-hydroxyhexadecanoylamino]-8-tetra-cosene-1,3,4-triol (Ⅰ) and 1-O-β-D-glucopyranosyl-(2S,3S,4R,8E)-2-[(2'R)-hydroxy-hexade-canoylamino]-8-tetracosene-1,3,4-triol (H) on the basis of chemical and spectroscopic studies.     

A convergent total synthesis of a new antiepileptic ceramide and its triacetyl derivative using olefin cross metathesis

A convergent total synthesis of a new antiepileptic ceramide 1b and its triacetyl derivative 1b′ was completed by using two important C-C bond forming reactions, Wittig methylenation and olefin cross metathesis as the key steps. The easily available 3,4,6-tri-O-benzyl-d-galactal was used as a chiral pool for the synthesis of highly functionalized amide 3 and the commercially available 1,12-dodecanediol for the long chain olefin counterpart 4. The long hydrocarbon chain of the new ceramide 1b was installed by using olefin cross metathesis between amide 3 and long chain terminal olefin 4 followed by hydrogenation.     

Phospholipase C-catalyzed sphingomyelin hydrolysis in a membrane reactor for ceramide production

A membrane reactor for the production of ceramide through sphingomyelin hydrolysis with phospholipase C from Clostridium perfringens was studied for the first time. Ceramide has raised a large interest as an active component in both pharmaceutical and cosmetic industry. The enzymatic hydrolysis of sphingomyelin has been proven to be a feasible method to produce ceramide. In the membrane reactor constructed, the aqueous phase and the organic phase were separated by a membrane containing the immobilized enzyme, while the organic phase was continuously circulated. Among the 10 selected membranes, the enzyme immobilized in membrane RC 70PP had low immobilization efficiency, but retained the highest catalytic activity. Three immobilization methods, i.e. filtration (adsorption/entrapment), covalent binding, and cross-linking, were compared. The enzyme immobilized by filtration had the highest activity even under the low fixation level (9.4%). The optimal flow rate of the organic phase was 5 ml/min. High initial enzyme amount in the immobilization led to the decrease in the fixation level. Both the initial reaction rate and the specific activity of the enzyme increased with increasing enzyme loading, and slightly decreased after the immobilized enzyme amount over 50 μg in 9.6 cm² membrane area. The immobilized enzyme retained 16% of the original activity after five cycles. Finally, the liquid enzyme, the enzyme immobilized on particle carriers, and the enzyme immobilized in the membrane were compared. The study demonstrated the improved enzyme reusability, the fast immobilization process, the straightforward up-scaling and the combination of the hydrolysis with the product separation in the membrane reactor developed.     

Isolation of ceramide fractions from skin sample by subcritical chromatography with packed silica and evaporative light scattering detection

Separative method of lipid classes from the stratum corneum was developed with packed silica and supercritical CO2 containing 10% of methanol at 15 degrees C, 15 MPa and 3 ml min(-1). The elution order of lipid classes was first esterified cholesterol, triglycerides, squalene co-eluted in a single peak, then free fatty acids, free cholesterol, ceramides and finally glycosylceramides. The ceramides were eluted in several fractions which depended on the number of hydroxyl groups in the molecule, i.e. more hydroxyl groups were contained in ceramides, more important was the retention. Moreover, the retention was not altered by the presence of carbon double bond and variation of the alkyl chain length. The ceramide response with the evaporative light scattering detector was improved by turning the influence of the solvent nature on the response to advantage. Therefore, addition of various solvents with or without triethylamine and formic acid were tested in post-column due to the incompatibility of such modifiers with silica stationary phase. Thereby the solvent conditions for the separation and the detection can be adjusted almost independently. The response was greatly increased by post-column addition of 1% (v/v) triethylamine and its equivalent amount of formic acid in dichloromethane introduced at 0.1 ml min(-1) into the mobile phase. This device had allowed the detection of 400 ng of ceramide with a S/N = 21, whereas no peak was observed in absence of the post-column addition. Finally, the method was applied to the treatment of skin sample which led to highly enriched ceramide fraction.     

The effects of transdermal permeation enhancers on thermotropic phase behaviour of a stratum corneum lipid model

This study evaluates the interactions of a model stratum corneum (SC) lipid system based on ceramide AP (N-(2-hydroxystearoyl)phytosphingosine) with three selected permeation enhancers including urea, oleic acid (OA), and N-lauroylglycine lauryl ester (12G12) using temperature-dependent small-angle X-ray diffraction measurements. As a first step, the thermotropic phase behaviour of the control SC lipid membrane, i.e. without enhancer, was characterized. The system shows two separated phases at 32 °C, which mix into another phase at around 45 °C. This phase is stable till 70 °C when the repeat distance starts to decrease. After cooling, only one phase is visible which shows two phase transitions at 45 and 70 °C again. Based on these results, the effects of the permeation enhancers were studied. The permeation enhancers influence the phase behaviour of the system. Urea and 12G12 cause a concentration-dependent shift of the phase transition temperatures while OA induces a phase separation. The results from this simple model system may provide basis for studies on more complex systems or real SC.     

Chromatographic lipid profiling of stress-exposed cells

Lipidomics is an emerging field of science not only due to its integral part of cell biology and biophysics but also due to the key role of lipids in the modulation of membrane physical properties, signaling, and cell death regulation. The aim of this study was to characterize changes in N-palmitoyl ceramide concentration and in the global lipid profile in macrophages challenged by oxidized low-density lipoprotein and nutrient deprived hepatocytes. For this purpose, a quantitative targeted method based on gas chromatography-mass spectrometry for the determination of total N-palmitoyl ceramide concentrations in the cellular membranes of cells under stress was used. Ultrahigh-performance liquid chromatography-quadrupole-time of flight mass spectrometry was applied for the comprehensive profiling of lipids. In essence, we found that both models of cellular stress caused an increase in N-palmitoyl ceramide levels. In addition, increased levels of other ceramides were observed as well as up- and down-regulation of several other lipid species.     

Interfacial behavior of glycosphingolipids and chemically related sphingolipids

Advances in understanding how glycosphingolipids and chemically related sphingolipids affect the structure and dynamics of bio-interfaces have been grouped in four inter-related areas: (a) influence of chemical structure in local interactions along lateral and transverse membrane planes; (b) effect of polar head group and hydrocarbon moieties on the mesomorphic state; (c) thermodynamic–geometric compensations affecting interfacial topology; and (d) domain segregation and surface topography.     

Syriacin, a novel unusual sulfated ceramide glycoside from the freshwater sponge Ephydatia syriaca (Porifera, Demospongiae, Spongillidae)

Syriacin, a novel unusual sulfated ceramide glycoside with branched very-long-chain fatty acid, i.e., (all Z)-34S-methylhexatriaconta-5,9,12,15,18,21-hexaenoic acid, has been isolated from the freshwater sponge Ephydatia syriaca. Its structure was identified by means of extensive spectroscopic analysis (IR, UV, 2D NMR, MS, CD) and chemical degradation. Syriacin showed antifeeding activity against goldfish at natural concentration (∼10 μg/ml).