Free sterols

The acetyl derivative is more easily reduced than the free sterol. 

F. J. Senorans, J. Tabera and M. Herraiz, Rapid separation of free sterols in edible oils by on-line coupled reversed phase liquid chr omatography-gas chromatography , 7. Agric. Food. Chem. 44 3189-3192 (1996). 

Ethanol and choline glycerolipids were isolated from calf brain and beef heart lipids by PTLC using silica gel H plates. Pure ethanol amine and choline plasmalogens were obtained with a yield of 80% [74]. Four phosphohpid components in the purple membrane (Bacteriorhodopsin) of Halobacterium halobium were isolated and identified by PTLC. Separated phosphohpids were add-hydrolyzed and further analyzed by GC. Silica gel G pates were used to fractionate alkylglycerol according to the number of carbon atoms in the aliphatic moiety [24]. Sterol esters, wax esters, free sterols, and polar lipids in dogskin hpids were separated by PTLC. The fatty acid composition of each group was determined by GC. 

Using PTLC six major fractions of lipids (phospholipids, free sterols, free fatty acids, triacylglycerols, methyl esters, and sterol esters) were separated from the skin lipids of chicken to smdy the penetration responses of Schistosoma cercaria and Austrobilharzia variglandis [79a]. To determine the structure of nontoxic lipids in lipopolysaccharides of Salmonella typhimurium, monophosphoryl lipids were separated from these lipids using PTLC. The separated fractions were used in FAB-MS to determine [3-hydroxymyristic acid, lauric acid, and 3-hydroxymyristic acids [79b]. 

The fourth isolated and identified compound from Palmer amaranth is chondri 11 asterol (5a-stigmasta-7,22-dien-30-ol), a sterol closely related structurally to the major plant sterols, stigmasterol and sitosterol. This compound, isolated as the free sterol, is not soluble in water or 0.1% DMS0, and germination bioassays required pretreatment of the test seed with a 0.1 mM solution of the sterol in DCM. 

Sterols are compounds that have a steroid structure (Figure 12.5) and contain a hydroxyl group, which is capable of forming an ester. They are widespread in nature and commonly exist as mixtures of the free sterol and esters with fatty acids. Cholesterol (Figure 12.5) is by far the commonest sterol in animals, a high concentration being found in brain, nervous tissue and membranes. Plants... 

In contrast to the other large cats, the urine of the cheetah, A. jubatus, is practically odorless to the human nose. An analysis of the organic material from cheetah urine showed that diglycerides, triglycerides, and free sterols are possibly present in the urine and that it contains some of the C2-C8 fatty acids [95], while aldehydes and ketones that are prominent in tiger and leopard urine [96] are absent from cheetah urine. A recent study [97] of the chemical composition of the urine of cheetah in their natural habitat and in captivity has shown that volatile hydrocarbons, aldehydes, saturated and unsaturated cyclic and acyclic ketones, carboxylic acids and short-chain ethers are compound classes represented in minute quantities by more than one member in the urine of this animal. Traces of 2-acetylfuran, acetaldehyde diethyl acetal, ethyl acetate, dimethyl sulfone, formanilide, and larger quantities of urea and elemental sulfur were also present in the urine of this animal. Sulfur was found in all the urine samples collected from male cheetah in captivity in South Africa and from wild cheetah in Namibia. Only one organosulfur compound, dimethyl disulfide, is present in the urine at such a low concentration that it is not detectable by humans [97]. 

We first studied the changes in free sterols of leaves and chloroplasts of beans and spinach exposed to ozone ( ). We found (Table IV) that ozonated bean leaves and chloroplasts had 25% and 12% less free sterols respectively than bean leaves and chloro-... 

Table IV, Changes in free sterol content of whole tissue and chloroplasts of bean and spinach leaves exposed to ozone (50 pphm for 1 hr)...

Loss of free sterol significant beyond 1% level. 

In another experiment (Table V), the free sterol content of ozonated chloroplasts from beans was found to be 32% less and the content of sterol derivatives 37% more than that of non-ozonated chloroplasts. What happens to the free sterols (FS), sterol glycosides (SG) and acetylated sterol glycosides (ASG) can be seen in Table VI, In these experiments ( ) with whole leaves of beans, FS in the ozonated leaves was 21% less, SG 32% more, and ASG 41% more than in non-ozonated leaves. 

One of the interesting effects of ozone is the 56% increase in the linolenic acid content of ASG from ozonated bean leaves ( ), This led us to explore the source of the additional linolenic acid, Ongun and Mudd ( ) had reported that SG and ASG normally formed at the expense of free sterols in non-ozonated plants. What happens in ozonated plants ... 

Table VI. Effect of ozonation (25 pphm for 2.5 - 3.0 hr) on free sterols (FS), sterol glycosides (SG), and acetylated sterol glycosides (ASG) in bean leaf tissue...

Halistanol sulfate (532) from Halichondria cf. moorei is a tris-sodium sulfate salt, which possesses antimicrobial, hemolytic, and ichthyotoxic activity [444]. It was later isolated from two sponges of the genus Topsentia as the free sterol and found to inhibit pp60v-src protein tyrosine kinase activity [445]. The tris(2-aminoimidazolium) salt of halistanol sulfate (533) was isolated from Topsentia sp. from Japan and is also antimicrobial [446]. 

In the intestine, saponins bind to mucosal cell membranes and change their physiology. Since the membranes of some cancer cells contain more cholesterol than do normal cells membranes [156], it is possible that saponins bind more to cancer cells and as a result induce their destruction. Since saponins are surface-active compounds that are not absorbed, their possible interaction with intestinal mucosal cell membranes must be emphasized. Because the average transit time of food is 24h, saponins can either in the intact or in the partly hydrolyzed form, remain in the intestine long enough to interact with free sterols and membrane lipids [157]. 

Figure D1.6.6 latroscan TLC-FID chromatograms of (A) a lipid fraction enriched with neutral lipids isolated from cod flesh and stored in ice (B) neutral lipids spiked with authentic 1 -0-palmityl-glyceryl ether dipalmitate (GE), coinciding in position with authentic highly unsaturated acids such as 22 6n-3 (C) hydrogenated neutral lipids spiked with GE. The solvent system was 97 3 1 (v/v/v) hexane/diethyl ether/formic acid for 40 min. Abbreviations O, origin SF, solvent front FFA, free fatty acid PL, phospholipids SE, steryl ester ST, free sterol TG, triglyceride. Reproduced from Ohshima et al. (1987) with permission from AOCS Press.

Many changes in the lipid composition of the plasma membrane have been associated with hardening (Lynch Steponkus, 1987). In rye (cv. Puma) an increase of the total lipid content has been measured during hardening (Cloutier, 1987). Free sterols increased while steryl-glycoside and acylated steryl-glycoside decreased. In addition the phospholipid contents of the plasma membrane increased. 

In the next part of our research on EBI-fungicides, we restricted ourselves to Pyricularia oryzae since from our point of view the In vitro results with that organism are representative and the test procedure is rather simple. The test chemical is applied in a suitable concentration to the culture medium which is then inoculated from an untreated pre-culture. After a 24-hour fermentation, the cells are separated from the culture filtrate by centrifugation, resuspended in a chloroform/methanol-mixture and homogenized using an ultraturrax treatment. After this extraction procedure, the sterol-conjugates are split to free sterols by a potassium-hydroxide treatment. Adsorption of the sterols to a Sep-pak column and step-wise desorption leads to a sterol fraction which can be analyzed directly by gas chromatography on a SE-30 capillary column. 

Roddick, J.G. Complex formation between solanaceous steroidal glycoalkaloids and free sterols in vitro. Phytochemistry 1979 18 1467-1470. 

The barrier properties of human skin have long been an area of multidisciplinary research. Skin is one of the most difficult biological barriers to penetrate and traverse, primarily due to the presence of the stratum corneum. The stratum cor-neum is composed of comeocytes laid in a brick-and-mortar arrangement with layers of lipid. The corneocytes are partially dehydrated, anuclear, metabolically active cells completely filled with bundles of keratin with a thick and insoluble envelope replacing the cell membrane [29]. The primary lipids in the stratum corneum are ceramides, free sterols, free fatty acids and triglycerides [30], which form lamellar lipid sheets between the corneocytes. These unique structural features of the stratum comeum provide an excellent barrier to the penetration of most molecules, particularly large, hydrophilic molecules such as ASOs. 

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