Liquid Ordered Phase of Binary Mixtures Containing Dipalmitoylphosphatidylcholine and Sterols

The effect of cholesterol, desmosterol, stigmasterol, sitosterol, ergosterol, and androsterol on the phase behavior of aqueous dispersions of dipalmitoylphosphatidylcholine (DPPC) was studied to understand the role of the side chain in the formation of ordered phases of the type observed in membrane rafts. Thermotropic changes in the structure of mixed dispersions and transition enthalpies were examined by synchrotron X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The observations indicated that cholesterol was more efficient than phytosterols (stigmasterol and sitosterol) or ergosterol in its interaction with DPPC to form the liquid ordered phase (L_o). The L_o induced by cholesterol or desmosterol was stable over a wide temperature range, whereas, the liquid ordered phase containing phytosterols or ergosterol was profoundly dependent on temperature, which should be distinguished as L_oβ and L_oα, representing the phases below and above the main transition temperature. The characteristics in forming ordered structures of cholesterol and other sterols imply that the evolution may have selected cholesterol as the most efficient sterol for animals to form rafts in their cell membranes.     

Development of a fast sample treatment for the analysis of free and bonded sterols in human serum by LC‐MS

The analysis of sterols in biological fluids allows the clinical study of cholesterol related diseases. This research is focused on reducing the sample processing time of the determination of free and bonded sterols in human serum. Ten sterols were studied: cholesterol precursors (desmosterol, lanosterol, and cholestanol); phytosterols (stigmasterol, campesterol, sitosterol, and sitostanol) and oxysterols (7‐α‐hydroxy‐4‐cholesten‐3‐one, 24‐hydroxycholesterol, and 27‐hydroxycholesterol). Ultrasound assistance was used to diminish the reaction time during the alkaline hydrolysis for determining total sterols. Different retention mechanisms of solid‐phase extraction were compared, two reversed‐phase sorbents DSC‐18 and polymeric Oasis‐HLB and a novel zirconia‐coated silica phase. DSC‐18 and zirconia‐coated silica were the most suitable sorbents to analyze these metabolites. The resulting extracts were analyzed by liquid chromatography coupled to mass spectrometry. The analytical parameters were determined and better values were observed with DSC‐18 cartridges for most sterols. LOQ were in the low ng/mL level. Recoveries were in the range 85–99%. Average intermediate precision was 15%. Accuracy for both cartridges was more than 92%. Zirconia‐coated silica showed better performance for the oxysterols, with recoveries around 90%. The procedure allows the determination of free and bonded sterol precursors, phytosterols, and oxysterols in human serum.     

侧扁软柳珊瑚中的3个甾醇

从中国南海侧扁软柳珊瑚(Subergorgia suberos)乙酸乙酯萃取相中首次分离得到3个甾醇化合物,根据现代波谱技术(MS,1D NMR,2D NMR)鉴定它们的结构,分别为:孕甾-5-烯-3-醇-20-羧酸(1),胆甾-3β,5α,6β-三醇(2),胆甾-22-烯-3β,5α,6β-三醇(3)。肿瘤活性实验表明,甾醇3对7种肿瘤细胞株的IC50值分别为:14.51、19.82、10.22、16.49、29.16、41.72与50.12μg/mL。     

Studies on the Steroids of Marine Sponge(Ⅳ)──Steroids from the Marine Spo

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Determination of fecal sterols in the sediments of different wastewater outputs by GC-MS

An improved method for the analysis of fecal sterols in sediments was applied to distinguish livestock wastewater, domestic sewage, and industrial wastewater pollution in the receiving waters of Taiwan’s rivers. The method included direct saponification, solvent phase extraction, derivatization with N-methyl-N-trimethyltrifluoroacetamide and catalyst, and separation by gas chromatography with an HP-50⁺ capillary column, followed by qualitative and quantitative analysis by mass spectrometry. Recoveries of nine sterols by this method were 78–89%. The indicators of biopollution markers ((coprostanone × coprostanol)/epicoprostanol) in different sources of wastewater effluents were calculated as human 0.913 ± 0.251, pig 0.224 ± 0.135, cow 0.023 ± 0.001, duck 0.007 ± 0.001; such indicators are feasible for distinguishing between different animal sources of fecal pollution in water.     

Chemical Constituents from Bletilla ochracea Schltr.

To study the chemical constituents in Bletilla ochracea Schltr.,repeated column chromatographies and preparative TLC were used for the isolation of compounds,and spectroscopic techniques(NMR,IR,UV and MS)were used for their structural identification.Seven compounds,2,7-bis(allyloxy)-5-methoxy-3-methyl-9,10-dihydrophenanthrene(1),gastrodin(2),gastrodigenin(3),β-sitosterol(4),stigmasterol(5),4-hydroxybenzaldehyde(6),and daucosterol(7)were obtained from the roots of B.ochracea Schltr.Compound 1 is structurally illustrated as a novel compound,and the others are isolated from the title plant for the first time.     

Comprehensive two-dimensional liquid chromatography×gas chromatography: evaluation of the applicability for the analysis of edible oils and fats

Edible fats and oils are complex mixtures containing a wide range of (classes of) compounds. The most important group of compounds are the triglycerides (triacylglycerides, TAGs). Because of the large number of possible fatty acid combinations, an enormous number of TAGs is possible. In the present feasibility study, the applicability of different modes of comprehensive two-dimensional LC×GC for detailed oil and fat analysis is evaluated. Comprehensive LC×GC was found to be an extremely powerful analytical method for the analysis of complex TAG samples. Using the new comprehensive set-ups, TAGs can be separated according to two independent parameters: carbon number vs. number of double bonds, or fatty acid composition vs. number of double bonds. The information content of comprehensive separations by far exceeds that of the current generation of analytical methods. The quantitative results of the separations show a good agreement with data obtained from standard analytical methods. The comprehensive methods studied can also be used for fingerprinting of oil samples, as well as for the analysis of target compounds or compound groups. Highly detailed separations of olive oil samples were obtained. Zooming in on one region of the chromatogram allowed reliable analysis of wax esters without interferences of sterol esters.     

24-Thiacycloartanol, a potent mechanism-based inactivator of plant sterol methyltransferase

The rationally designed substrate mimic of cycloartenol, 24-thiacycloartanol (24-TC) 4A, and its corresponding sulfonium salt 5A were tested against the recombinant sterol methyltransferase (SMT) from Glycine max (soybean). Analog 4A was found to irreversibly inactivate the enzyme generating competitive- and time-dependent inhibition of activity accompanied by a K_i value of 2 μM and k_inact of 0.3 min⁻¹. Analog 5A, a presumptive high-energy intermediate of the SMT catalyzed reaction, was found to be a reversible, non-competitive-type inhibitor generating a K_i value of 55 nM.     

含脂肪食品中植物甾醇含量的气相色谱法测定

建立了一种利用气相色谱测定含脂肪食品中植物甾醇含量的方法。样品加入β－胆固醇作内标,70℃下在KOH－EtOH溶液中皂化1h,用正己烷萃取,采用毛细管气相色谱法测定甾醇含量。该法具有良好的准确度和精确度。     

软骨凹顶藻Laurencia Cartilaginea 甾醇成分的研究

从中国南海软骨凹顶藻乙醇浸提物的乙酸乙酯相中 ,首次分离得到一种环二氧麦角甾醇 :5α,8α-环二氧麦角甾 - 6 ,2 2 -二烯 - 3β-醇 (1)。通过 GC- MS方法检测到了其他 5种甾醇化合物 :5 ,8-环二氧麦角甾 - 1,6 ,2 2 -三烯 - 3-醇 (2 ) ,麦角甾 - 6 ,2 2 -二烯 - 5 ,8-二羟基 - 3-酮 (3) ,豆甾 - 6 ,2 2 -二烯 - 5 ,8-二羟基 - 3-酮 (4) ,麦角甾 -5 ,7,9(11) ,2 2 -四烯 - 3-醇 (5 )以及豆甾 - 5 ,7,2 2 -三烯 - 3-醇 (6 )