Origin Of Sterols Research Articles

Polar non-hydrocarbon contaminants in reservoir core extracts

A geochemical investigation of oils in sandstone core plugs and drill stem test oils was carried out on samples from a North Sea reservoir. A sample of diesel used as a constituent of the drilling fluids was also analysed. The aliphatic and aromatic hydrocarbons and polar non-hydrocarbons were isolated using solid phase extraction methods. GC analysis of the hydrocarbon fraction of the core extract indicated that contamination may be diesel derived. From analysis of diesel some compound classes are less likely to be affected by contamination from diesel itself including: steranes, hopanes, aromatic steroid hydrocarbons, benzocarbazoles and C0–C3-alkylphenols.Large quantities of sterols (ca. 30 mg g-1 total soluble extract) were identified in the polar non-hydrocarbon fractions of the core extract petroleum, presumably resulting from contamination. The origin of sterols is likely to be due to an additive introduced into the drilling fluid. Sterols are surface active compounds and in significant quantities may affect engineering core property measurements including wettability determinations. In addition, bulk petroleum composition screening methods, such as Iatroscan, used for determining saturated and aromatic hydrocarbons, resins and asphaltenes (SARA) content of core extract petroleum may also be affected.

The Biosynthesis, Absorption and Tissue Distribution of Dietary Shellfish Sterols in the Crab

AbstractThe present paper deals with the biosynthesis, absorption and tissue distribution, and the origin of sterols in the crabs, Cancer majester. After the administration of isotopic mevalonate and isotopic cholesterol to crabs, the sterols were isolated by the digitonine method. The identification and sterol compositions were determined by gas‐liquid chromatography, and gas chromatography‐mass spectrometry.The results indicated that C. majester fail to utilize mevalonate to synthesize cholesterol, and are incapable of the bioconversion of cholesterol to other sterols. The sterols found in their tissues may originate from dietary sources.

The biosynthesis, absorption, and origin of cholesterol and plant sterols in the Florida land crab.

In order to study the biosynthesis, composition, and origin of sterols in the Florida land crabs, Cardisoma guanhumi (Latreille), we fed 17 male crabs either a cholesterol-free or a high cholesterol diet for 2 to 7 weeks. The origin of sterols in these crabs, whether from biosynthesis or from the diet, was determined by tahree procedures: the incorporation of isotopic mevalonate into the cholesterol when the diet was cholesterol-free; the absorption of isotopic cholesterol and sitosterol from the diet; the cholesterol and plant sterol concentrations of hepatopancreas, plasma, and muscle under conditions of cholesterol-free and high cholesterol diets. In addition, the interconversion of cholesterol and sitosterol was investigated. Dietary sterols of plant and animal sources were readily absorbed and provided the major source of sterols for this species of crab. The biosynthesis of cholesterol from mevalonate in this crab was minimal. However, cholesterol was synthesized from dietary sitosterol by dealkylation. Cholesterol and the three plant sterols (24 epsilon-methyl cholesterol, stigmasterol, and sitosterol) were found in the hepatopancreas, plasma, and muscle of the crab. Plant sterols contributed from 9 to 37% of the total sterols in the hepatopancreas, plasma, and muscle of the crabs fed a cholesterol-free diet.

Intracellular distribution and origin of sterols in Calendula officinalis leaves

In Calendula officinalis leaves 66% of all steryl forms are present in the ‘microsomal fraction’ (IV), 24% in the mitochondrial and Golgi membranes (III), 5% in the ‘chloroplast’ (II), 4% in the ‘cell wall and membrane’ (I) fraction and 1%. in the cytosol. Free sterols, their esters, glycosides and acylated glycosides are present in varying proportions in all cellular subtractions. Mevalonate-[2 14C] labelling of sterols derived from various steryl forms showed that free sterols and all their derivatives, i.e. steryl esters and glucosides, are formed in fraction IV and are then translocated to other organelles. Fraction III is the main site of glycosylation of transported sterols as well as of acylation of steryl glycosides.

Origin of sterols in uredospores of Uromyces phaseoli

The sterols from healthy bean leaves are β-sitosterol, stigmasterol, campesterol and 28-isofucosterol. An additional sterol observed in bean leaves infected with Uromyces phaseoli was identified as 7,( Z)-24(28)-stigmastadien-3β-ol, which is the major sterol of the uredospores of the fungus. The fungus appears to stimulate sterol synthesis, but most of the increased sterol content of infected leaves can be attributed to the sterol of the uredospores.