Single-cell proteins from methanol: elucidation of the structures of the unsaturated fatty acids

Abstract

The unsaturated fatty acids contained in single-cell proteins prepared from Li 70 yeasts grown on methanol were studied in order to ascertain the position of unsaturation and the stereochemistry of the double bonds. The acids were extracted and esterified to the corresponding fatty acid methyl esters (FAMEs) as described in previous reports. The location of the double bonds was obtained by gas-chromatographicmass-spectrometric analysis of the trimethylsilyloxy derivatives of the FAMEs. The stereochemistry was deduced by nuclear magnetic resonance spectroscopy using an incremental addition study with Eu(fod), on FAMEs and on the corresponding epoxy derivatives. Three model FAME samples, methyl oleate (~c-C,,:,), methyl elaidate (9t-C18:,) and methyl linoleate (gc, 1 2 ~-C ~~: ~) , were compared. Most of the unsaturated fatty acids (about 74%) present in the single-cell proteins have structures identical with those known in animal lipids. The three most abundant unsaturated fatty acids display the following structure : ~C -C ~~: ~ (22.5y0), 9c-Cl8:, (19.4%) and 9 ~, 1 2 c -C , ~: ~ (29.2%). All double bonds possess a cis-configuration; the position of the double bond is a t C9-C10 for the monounsaturated acids and C9-C10 and C12-Cl3 for diunsaturated acids.

Chemical constituents of Dolichos lablab (field bean) pod exudate

“…The spectral characteristics of the two esters along with the mass spectral data of their TMSO derivatives are summarized in Table IV. Recently there have been many reports of the successful application of TMSO derivatives of unsaturated fatty acid esters using mass spectral analysis to locate the double bond position in the fatty acid chain (Capella and Zorzut, 1968;Dommes et al, 1976;Cavalli et al, 1978). The mass spectra of the TMSO derivatives of both C-12:l and C-14:l acid methyl esters show no molecular ion peak, but an M -CH3 peak due to loss of CH3 radical from the trimethylsilyl group.…”

Isolation and structure elucidation of four fatty acid derivatives of the mycotoxin fusarochromanone produced by Fusarium equiseti

“…Three milligrams of TDP-9 was hydrolyzed according to the method described above. Trimethylsilyloxy (TMSO) derivatives of methyl esters of the unsaturated fatty acids obtained from the hydrolysis of were prepared by hydroxylation of the olefinic bond by oxidation with 0s04 and subsequent reduction of the osmates with NasSOs, generally following the procedure described by Cavalli et al (1978). The hydrolysis product was dissolved in 2 mL of pyridine-dioxane (1:8) and treated with 20 mg of 0s04 (2% solution in dioxane).…”