Reactivity of key metabolic sterols in standard colorimetric assays for cholesterol

Abstract

The reaction of lanosterol, desmosterol and 7-dehydrocholesterol, key intermediates in cholesterol biosynthesis, were-compared with cholesterol in 3 standard colorimetric assays for cholesterol based on formation of chomogens with acetic anhydride, ferric chloride and ferrous sulfate. Marked differences in the reaction of the sterols in the different assays were due both to formation of chomogens with qualitatively similar spectral patterns but with greatly different extinctions and to formation of chromogens with clearly different absorption maxima. For example, in all assays, cholesterol and desmosterol formed chromogens with very similar absorption spectra but with varying extinctions, whereas the lanosterol chromogen in all assays was different from cholesterol's in both absorption maxima and in extinctions. The findings show that attempts to measure tissue sterol levels by colorimetric methods can result in greater errors when cholesterol is not the sole sterol. Also, the unique spectral properties of the lanosterol chromogen formed in the Liebermann-Burchard reaction (a sharp absorption peak at 450 nm) suggests the possible use of this method as a qualitative test for lanosterol.

Tissue cholesterol content alterations in streptozotocin-induced diabetic rats

“…The method [24,25] used in these studies was that the reaction of cholesterol in the presence of an FeCl 3 -H 3 PO 4 -H 2 SO 4 mixture forms a colored complex, which was measured using spectrophotometer. A previous study proved that other sterols might interfere with the quantification of cholesterol by this method, thus resulting in large errors [26] . Another report also showed that the colorimetric method would generate a value roughly 50% higher than other methods [27] .…”

Ultraviolet and light absorption spectrometry

“…Complexon III has been used in conjunction with carbon tetrachloride extraction followed by treatment with dithizone to determine 10-chlorophenoxarsine and bis (tributyltin) oxide in aqueous solution in the presence of one another (550). The reactivity of lanosterol, desmosterol, and 7-dehydrocholesterol, key intermediates in cholesterol biosynthesis, have been compared in three standard colorimetric assays for cholesterol based on formation of chromogens with acetic anhydride, iron(III) chloride, and iron(II) sulfate (451). Two studies of the colorimetric assay for glycosylated hemoglobin which involve the production of 5-hydroxymethylfurfural by hydrolysis, which attempt to evaluate the effect of various parameters and their standardization within the method, have been reported (350,494).…”

Lipids in Human Milk

“…The amounts of total choles terol in milk ha ve been reported as ranging from 200 to 1,330 mg/tOO g of lipid (4), but much of this vari ation can be attributed to use of non specific colorimetric methods for determination of the sterol and , again , improper sampling. Sarkar and Cenedella (32) observed that attempts to measure tissue cholesterol levels by colorimetric procedures result in subs ta ntial error s whe n lanosterol, desmosterol, and 7-deh ydrocholesterol are present. They and we recommend gasliquid chomatography (GL C) a s the analy tical method of choice.…”