NMR measurement of free and esterified sterols

ABSTRACTThe goal of this study is the selective oxyfunctionalization of steroids under mild and environmentally friendly conditions using fungal enzymes. With this purpose, peroxygenases from three basidiomycete species were tested for the hydroxylation of a variety of steroidal compounds, using H2O2as the only cosubstrate. Two of them are wild-type enzymes fromAgrocybe aegeritaandMarasmius rotula, and the third one is a recombinant enzyme fromCoprinopsis cinerea. The enzymatic reactions on free and esterified sterols, steroid hydrocarbons, and ketones were monitored by gas chromatography, and the products were identified by mass spectrometry. Hydroxylation at the side chain over the steroidal rings was preferred, with the 25-hydroxyderivatives predominating. Interestingly, antiviral and other biological activities of 25-hydroxycholesterol have been reported recently (M. Blanc et al., Immunity 38:106–118, 2013,http://dx.doi.org/10.1016/j.immuni.2012.11.004). However, hydroxylation in the ring moiety and terminal hydroxylation at the side chain also was observed in some steroids, the former favored by the absence of oxygenated groups at C-3 and by the presence of conjugated double bonds in the rings. To understand the yield and selectivity differences between the different steroids, a computational study was performed using Protein Energy Landscape Exploration (PELE) software for dynamic ligand diffusion. These simulations showed that the active-site geometry and hydrophobicity favors the entrance of the steroid side chain, while the entrance of the ring is energetically penalized. Also, a direct correlation between the conversion rate and the side chain entrance ratio could be established that explains the various reaction yields observed.

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Effect of esterified 4-desmethylsterols and -stanols or 4,4′-dimethylsterols on cholesterol and bile acid metabolism in hamsters

British Journal Of Nutrition ◽

10.1079/bjn2001509 ◽

2002 ◽

Vol 87 (3) ◽

pp. 227-237 ◽

Cited By ~ 26

Author(s):

Elke A. Trautwein ◽

Claudia Schulz ◽

Dörte Rieckhoff ◽

Angelika Kunath-Rau ◽

Helmut F. Erbersdobler ◽

...

Keyword(s):

Bile Acid ◽

Acid Metabolism ◽

Ldl Cholesterol ◽

Cholesterol Absorption ◽

Bile Acid Metabolism ◽

Acid Excretion ◽

Hepatic Cholesterol ◽

Intestinal Cholesterol Absorption ◽

Cholesterol Lowering ◽

Esterified Sterols

4-Desmethylsterols and -stanols reduce plasma total cholesterol (TC) and LDL cholesterol by inhibition of intestinal cholesterol absorption, while the cholesterol-lowering potential of 4,4′-dimethylsterols is less well defined. The present study aimed to compare the effects of 4-desmethylsterols, -stanols, and 4,4′-dimethylsterols on plasma and hepatic cholesterol, sterol excretion and bile acid metabolism. Male golden Syrian hamsters were fed diets containing 13 g/100 g fat, 0·08 g/100 g cholesterol and 0 (control), 0·24 or 0·48 % (w/w) esterified 4-desmethylsterols (sterols) and esterified hydrogenated 4-desmethylsterols (stanols) from common vegetable oils or esterified 4,4′-dimethylsterols from rice bran oil for 5 weeks. Sterol and stanol esters at the dose of 0·24 % were equally effective and significantly (P<0·05) lowered TC by 15 %, while 0·24 % 4,4-dimethylsterols reduced TC by 10 %. Liver total and esterified cholesterol concentrations were significantly (P<0·05) lowered by 40, 22, 43 and 31 % in hamsters fed 0·48 % sterols, 0·24 % stanols, 0·48 % stanols or 0·48 % dimethylsterols, respectively. Daily faecal bile acid excretion and hepatic cholesterol 7α-hydroxylase activity were not altered, indicating that sterols, stanols and dimethylsterols had no effect on the intestinal re-absorption of bile acids or on hepatic bile acid synthesis. Daily excretion of cholesterol was significantly higher in hamsters fed esterified sterols and stanols, but was only slightly increased in those fed dimethylsterols. The results indicate that esterified sterols and stanols were equally effective in lowering plasma TC and LDL cholesterol, while dimethylsterol esters caused a weaker cholesterol-lowering effect. Sterols and stanols achieve their cholesterol-lowering effect by stimulating faecal cholesterol excretion through inhibiting intestinal cholesterol absorption, but do not affect bile acid excretion. Other mechanisms need to be considered to explain the effect on plasma and hepatic cholesterol of dimethylsterols.

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Influence of the vegetable oil refining process on free and esterified sterols

Journal of the American Oil Chemists Society ◽

10.1007/s11746-002-0585-4 ◽

2002 ◽

Vol 79 (10) ◽

pp. 947-953 ◽

Cited By ~ 91

Author(s):

T. Verleyen ◽

U. Sosinska ◽

S. Ioannidou ◽

R. Verhe ◽

K. Dewettinck ◽

...

Keyword(s):

Vegetable Oil ◽

Refining Process ◽

Oil Refining ◽

Esterified Sterols ◽

Vegetable Oil Refining

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Fluorescence studies of protein–sterol relationships in human plasma lipoproteins

Biochemical Journal ◽

10.1042/bj1370413 ◽

1974 ◽

Vol 137 (2) ◽

pp. 413-415 ◽

Cited By ~ 31

Author(s):

Rory J. M. Smith ◽

Colin Green

Keyword(s):

High Density Lipoprotein ◽

Human Plasma ◽

Low Density Lipoprotein ◽

Density Lipoprotein ◽

Tryptophan Fluorescence ◽

High Density ◽

Plasma Lipoproteins ◽

Low Density ◽

Fluorescence Studies ◽

Esterified Sterols

Cholesta-5,7,9(11)-trien-3β-ol and its oleate ester were incorporated into human low-density lipoprotein and reconstituted high-density lipoprotein. The unesterified sterol was more efficient than its ester in quenching tryptophan fluorescence, especially in low-density lipoprotein. The results, which indicate that in such lipoproteins unesterified sterols are more closely associated with peptide than are esterified sterols, are used to assess possible structures for the lipoproteins.

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Mode of formation of cholesta-5,7-dien-3β-ol from cholest-5-en-3β-ol by larvae of Calliphora erythrocephala

Biochemical Journal ◽

10.1042/bj1520303 ◽

1975 ◽

Vol 152 (2) ◽

pp. 303-311 ◽

Cited By ~ 19

Author(s):

Paul Johnson ◽

Ian F. Cook ◽

Huw H. Rees ◽

Trevor W. Goodwin

Keyword(s):

Hydrogen Atom ◽

Bond Formation ◽

Calliphora Erythrocephala ◽

Probable Role ◽

Esterified Sterols

1. The conversion of cholest-5-en-3β-ol (cholesterol) into cholesta-5,7-dien-3β-ol by axenic Calliphora erythrocephala larvae was demonstrated. 2. The transformation is probably direct (Δ5→Δ5,7) and does not involve a Δ0 intermediate (Δ5→Δ0→Δ7→ Δ5,7). 3. Δ7-bond formation involves the stereospecific elimination of the 7β hydrogen atom. 4. The relative amounts of free and esterified sterols were determined in larvae grown on cholesterol as sole sterol source and on 5α-cholestan-3β-ol supplemented with minimal amounts of cholesterol. 5. The significance of the results is assessed in relation to the probable role of cholesta-5,7-dien-3β-ol as an intermediate in the biosynthesis of ecdysones.

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Observations on the effect of the rediae of Fasciola hepatica on the lipid composition of the hepatopancreas of Lymnaea truncatula

Parasitology ◽

10.1017/s0031182000041123 ◽

1970 ◽

Vol 61 (2) ◽

pp. 293-299 ◽

Cited By ~ 11

Author(s):

V. R. Southgate

Keyword(s):

Fatty Acids ◽

Fatty Acid ◽

Neutral Lipid ◽

Total Lipid ◽

Phosphatidyl Choline ◽

Fasciola Hepatica ◽

Dry Weight ◽

Major Fatty Acid ◽

Total Fatty Acids ◽

Esterified Sterols

In the uninfected hepatopancreas of L. truncatula 7·0–11·0% of the dry weight is lipid. Of the total lipid 60% is neutral lipid and 40% is phospholipid. Free fatty acid is the major neutral lipid component; triglycerides, diglycerides, monoglycerides, sterols and esterified sterols are also present. The phospholipids identified were phosphatidyl choline, phosphatidyl ethanolamine, lyso-phosphatidyl choline and sphingomyelin. The fatty acids were analysed by gas chromatography. The major fatty acid is C16 (palmitic) and 60% of the total fatty acids are saturated.In the hepatopancreas of L. truncatula infected with the rediae of F. hepatica, but with the rediae removed, 5·4–9·4% of the dry weight is lipid. Of this total lipid 73% is neutral lipid and 27% is phospholipid. All the fractions of neutral lipid, except the fatty acids are smaller than in the uninfected hepatopancreas. The fatty acids show an increase of 38%. The same phospholipids identified in the uninfected hepatopancreas are present, but all the fractions show a decrease in amount with the exception of the phosphatidyl choline fraction, which is present in approximately equal amounts in both the uninfected and the infected hepatopancreas. The major fatty acid is palmitic acid.

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