John D. Gilbert

Lipids of human atheroma Part 4. Characterisation of a new group of polar sterol esters from human atherosclerotic plaques

Abstract Lipid extracts from plaques of grossly diseased human aortas were fractionated by silicic acid column chromatography. Examination of selected fractions by thin-layer chromatography revealed the presence of a number of esters with polarity intermediate between that of the triglycerides and cholesterol. Acetylation of this group of compounds decreased their polarity, thus suggesting the presence of free hydroxyl groups. Alkaline hydrolysis established that the main neutral component was cholesterol, accompanied by smaller amounts of 26-hydroxycholesterol, 7β- and 7α-hydroxycholesterol and a 24-hydroxycholesterol. The polarity of the cholesterol esters was due to their acyl moieties: three of the constituent acids have been identified as two isomeric 9-hydroxyoctadeca-10,12-dienoic acids and a 13-hydroxyoctadeca-9,11-dienoic acid. The polar sterol esters constitute a new group of lipids associated with human atheroma. The possible role of peroxidised linoleates in the formation of these compounds is discussed.

Lipids of human atheroma: VIII. Oxidised derivatives of cholesteryl linoleate

Abstract Cholesterol linoleate hydroperoxides, isolated from the lipids of advanced atherosclerotic plaques of human aortas obtained during post mortem examination, have been shown to comprise a mixture of 9- and 13-hydroperoxides similar to those produced by autoxidation. Corresponding 9- and 13-keto-octadecadienoates, found in variable amounts in plaque lipids, may be satisfactorily separated by preparative thin-layer chromatography after selective reduction of the accompanying hydroperoxides with SnCl 2 . The two classes of oxidised linoleate were characterised in the form of the diols produced by reduction with LiA1 2 H 4 , using combined gas chromatography-mass spectrometry. Gas-liquid chromatography of the drimanoate esters of methyl 13-hydroxystearate derived from arterial hydroxycholesterol esters indicated a 1:1 ratio of the 13−( S )- and 13−( R )-derivatives.

Lipids of human atheroma Part 5. The occurrence of a new group of polar sterol esters in various stages of human atherosclerosis

Abstract A considerable amount of cholesterol esters of 9- and 13-hydroxyoctadecadienoic acids was detected in the more advanced stages of human aortic atheroma. Esters of this class were not detectable in “early” lesions, but formed an increasing proportion of the total extractable lipid material with increasing severity of atheroma. The possible significance of this correlation is discussed.

Lipids of human atheroma vii. isolation of diesters of cholest-5-ene-3β,26-diol from extracts of advanced atherosclerotic lesions of human aorta

Abstract Investigations of minor lipids in human atherosclerotic lesions have led to the isolation of a group of sterol esters, different in character from those previously described. Hydrolysis and reductive cleavage of these compounds indicates that they are diesters of cholest-5-ene-3β,26-diol. The preponderant acyl moieties are oleate and palmitate.

Absolute Configuration OP Secondary Alcohols: Refinement and Extension of a Gas-Chromatographic Modification of Horeau's Method

Abstract In our adaptation of Horeaus method of partial kinetic resolution, excess α-phenylbutyric anhydride is converted to diastereomeric amides for determination of its optical composition by gas-liquid chromatography. A modified procedure allows the use of as little as 1 μmole of substrate. The validity of configurational assignments based on these methods has been explored for a wide range of chiral alcohols, including a number of alkaloids. Important areas of potential application of the new procedures are delineated.

Absolute configurations of secondary alcohols. A gas chromatographic modification of Horeau's method

Gas chromatographic determination of diastereoisomeric amides of (+)- and (–)-α-phenylbutyric acid permits the simple application of Horeaus method to small quantities (10µmole) of chiral secondary alcohols.