Steryl acetates

Cell suspension cultures of Gypsophila paniculata and Saponaria officinalis produce very closely related triterpenoid saponins. Pretreatment of cell suspension cultures of G. paniculata with gypsogenin 3,0-glucuxonide (a triterpenoid saponin precursor in G. paniculata) followed by administration of [ C] acetate resulted in a marked reduction in incorporation of radioactivity into saponins and their precursors, but not into sterols and steryl glycosides [26]. Measurements of OSC activities revealed that there was no effect of elicitor treatment on CS levels in either species, but in G. paniculata AS levels went down while in S. officinalis they increased. This suggests that in these two species OSCs are regulating steps in the isoprenoid pathway and control the flux to sterols and triter-penes. 

NP-HPLC Normal-phase liquid chromatographic methods applying Diol-columns or common silica columns are well suited for the analysis of the total steryl ferulate content. They require very little sample preparation, as total lipid extracts can frequently be directly injected into the column without purification or fractionation. Run times for SFs are also relatively short, and a good separation from other lipid components can be obtained in less than 10 min in traditional HPLC systems. Depending on the column type and the sample, SFs elute as one or two peaks. Two peaks are obtained from the separation of SFs, which have ferulic acid both in cis- and trans- configuration (Nystrom et ah, 2008). The relative retention time (obtained with a silica column and hexane/ethyl acetate 97 3 as eluent) of the cis- form is about 0.5 smaller than that of steryl irans -ferulates (Akihisa et al., 2000). 

To determine sterols, a portion of the total lipid extract is saponified using methanolic potassium hydroxide, and sterols subsequently recovered in 2 1 hex-ane/chloroform. The sterols are converted to the corresponding trimethylsilyl (TMS) ethers using bis-N,0-(trimethylsilyl)trifluoroacetamide, BSTFA, and analyzed by capillary GC and GC with mass spectrometry. Reviews of relative retention times and mass spectra for sterol TMS ethers have been published [e.g. 73]. In some cases, sterol acetates, rather than TMS ethers, are the derivatives prepared for GC. SiHca column chromatography of the total lipid extract may also be used instead of saponification to isolate the sterol fraction [74], or even sterol subclasses such as 4,4-dimethyl, 4-monomethyl and 4-desmethyl sterols [75], prior to derivatization. However, this approach only includes free sterols in the analysis, whereas by saponifying the total extract, sterols present as steryl esters are also detected. 

Ibn steryl ferulate and coumarate esters were extracted from com and rice and were identified using a C g column (A = 325 nm) and an 82/3/2/13 acetonitrile/1-butanol/acetic acid/water mobile phase. Good resolution was obtained and the elution was complete in 35 min. Chromatograms showing the effects of varying water level (1-21%) on peak shape and resolution were shown. Levels from 70 pg to 26mg/g sample were tabulated [1065]. 

Fig. 135. Thin-layer chromatogram of the lipids from human tissue [202]. Adsorbent silica gel G solvent petrol ether (BP 60—70° C)-diethyl ether-acetic acid (90 + 10 -f 1) time of run 1 h visualisation carbonisation by heating with chromic acid/sulphuric acid amounts ca 200 (xg of each 1 artificial mixture (cholesterol, oleic acid, triolein, methyl oleate and chole-steryl oleate) 2 serum 3 aorta calcification 4 liver 5 kidneys 6 depot fat 7 bone marrow 8 artificial mixture (lecithin, cholesterol, oleic acid, triolein and cholesteryl oleate)...

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