Studies were conducted to find components involved in the UV-active (at 233 nm) polar triglyceride fractions, which had been used previously for evaluation of heat treated frying oils. Polar triglyceride fractions prepared from 2030 hr heat treated soybean oils by frying varied food items were first fractionated on a Bio-beads column; major fractions were F2 with a molecular weight range of 400022000 (841% in oil samples, depending on food items used) and F3 with 2200600 (321). These two fractions prepared from oils by frying whale meat, mackerel, and moist cotton ballss were further fractionated by silicagel column chromatography ; a major fraction (712% in oil samples from F2 and 13% from F3) was least UV-active, in general, followed by the most UV-active fractions (27% from F2 and 13% from F3). A ratio of polar fatty acid esters (PFA) to apolar esters from these UV-active subfractions was approximately 1 : 2. GC-MS of PFA demonstrated the presence of the following types of compounds : Short chain esters having at their terminal ends a diol-keto group, a triol, a dicarbonyl-hydroxy or -keto ; 12, 13-epoxyoctadecanoate, 9, 12-epoxyocta-decanoate, and a small amount of 9, 13-epoxyoctadecanoate; and mixtures of cyclic monomeric compounds having polar functional groups.
In a previous paper, we reported that linseed oil heated in an inert gas showed toxicity to mice and the skeletal structures of toxic compounds were methyl 9-(2′-n-propylcyclohexyl) nonanoate and/or methyl 8-(2′-n-butylcyclohexyl) octanoate and contained two double bonds. Moreover, the authors noticed the presence of four positional isomers of the double bonds. To know toxic effects of cyclic fatty acids, feeding experiments were carried out. Rats were given a diet containing 2.24.9% cyclic fatty acids for three weeks and the inhibition of body weight gain, hypertrophy and/or hyperplasy of liver, and a little decrease of digestibility were observed. Analyses of liver lipids revealed the symptom of fatty liver accompanied by the increase of neutral lipids and phospholipids. Histopathological changes were also observed in nuclei, cytoplasms and intercellular substances of liver cells by histological examination. To investigate the absorption of cyclic fatty acids which caused pathological changes, component fatty acids of plasma and liver lipids were determined by gas chromatography-mass spectrometry (GC-MS). The presence of these cyclic fatty acids was observed in both plasma and liver. This result indicated the possibility of the absorption of these cyclic fatty acids through small intestine. Furthermore, cyclic fatty acids were also found in neutral lipids, phospholipids and cholesteryl esters fractions of liver lipids. To know the relationship between the skeletal structure of cyclic fatty acids and toxicity, cyclic fatty acids were reduced and administered orally to mice. The hydrogenated cyclic fatty acids showed less toxicity than the original acids. From these results, we concluded that cyclic fatty acids are absorbed through small intestine and cause fatty liver and the other histopathological changes. Thus one of the reasons for the toxic effect of cyclic fatty acids is attributable to the metabolic injury in liver.
The reaction of 1, 2-epithiodecane (I) with methanol in the presence of sulfuric, p-toluenesulfonic, and methanesulfonic acids gave a mixture of 2-methoxy-1-decanethiol (II), 1-methoxy-2-decanethiol (III), and a polymer. The ratio of the yields of II and III was little changed with the reaction conditions such as reaction temperature, reaction time, and kinds and amounts of acids, and it was about 6 : 4. Each NMR spectrum of the polymers formed under various conditions showed that the ratio of [CH3- (CH2)7, -CH-CH2-] / [CH3O-] was 24. The reaction of 1, 2-epithiooctane, 1, 2-epithiododecane, and 1, 2-epithiotetradecane with methanol, and I with other primary alcohols in the presence of sulfuric acid gave similar results described above. On the other hand, the reaction of I with secondary alcohols in the presence of sulfuric acid gave almost the same amounts of 2-alkoxy-1- and 1-alkoxy-2-decanethiols. The reactivities of alcohols to 1, 2-epithioalkanes were primary > secondary>tertiary alcohols.
Methods for the determination of sterols in edible oils and fats were studied. The sterols were isolated and analysed by the method of thin layer chromatography or digitonin precipitation, coupled with gas liquid chromatography, respectively, with using cholesterol or β-sitosterol as an internal standard. Quantitative determination of sterols was made by cutting off the peaks of cholesterol and phytosterol on the recorded papers from the gas chromatograms recorded with and without the presence of the internal standard, and followed by the calculation of the changes in the peak weight caused by the addition of the standard. Recovery experiments were carried out by eight collaborators (totalling 10) with samples of medium-chain triglyceride added with a known concentration of cholesterol and phytosterol. Mean recovery rate was over 81.4%, and it was found that even 10 mg of cholesterol contained in 100 g of oil or fat was determined with a relatively good reproducibility. Both the methods of the thin layer chromatography and the digitonin precipitation coupled with gas liquid chromatography gave satisfactory results.
A high-speed liquid chromatography with n-hexane (H) and diisopropyl ether (IPE) solvent, Hitachigel # 3040 column packing and a UV monitor (295 nm) permits a rapid and reliable method for the analysis of tocopherol dimers. Tocopherol dimers used in this study were shown in Table-1. Separation of tocopherols and their dimers was obtained by eluting with a mixture of n-hexane-diisopropyl ether 90 : 10 except the separation of compounds 5- (-tocopheroxy) -γ-tocopherol (4) and 5- (γ-tocopherol-5'-yl) -γ-tocopherol (5). (Fig.-1) The distinct separation of compound (4) and (5) was achieved with a mixture of n-hexanediisopropyl ether 98 : 2 (Fig.-2).
The trans isomers present in fats and oils can be determined by the rapid liquid-film method from measurements of the infrared absorption at two wavelengths, one due to trans conformation of the double bond and the other due to ester group. The ratio of the two absorbances has a linear relationship with the trans isomer content. This method thus provides a simple determination of trans isomer without weighing in accuracy or messing up an exact volume.
Formerly, the authors found that tocopherol in the fats with low iodine value decomposes more rapidly than that in the fats with high iodine value during the course of thermal oxidation. This result was just the opposite of what was expected from the result of the decrease of tocopherol content accompanied by the autoxidation of several fats. In this study, the relation between the degree of unsaturation of triglyceride and thermal oxidation of tocopherols was examined with synthesized saturated and unsaturated triglycerides (1-lauroyl-2, 3-dipalmitin (LaPP), 1-lauroy-2, 3-dilinolein (LaLL) and trilinolein (LLL)). When triglycerides, in which γ-tocopherol was added at the concentration of about 0.07 %, were heated in an oil bath controlled at 180°C under the condition of specific surface area 0.45 cm2/g, the decreasing velocity of γ-tocopherol concentration, which was determined by both a colorimetry based on Emmerie-Engel reaction and a gas-chromatography, in unsaturated triglyceride was slower than that in saturated triglyceride. Thermal oxidation of α-and δ-tocopherols in unsatuarted triglyceride was also lower than that in saturated triglyceride. This fact confirmed that the stability of tocopherol in the fats is strongly affected by the degree of unsaturasion of triglycerides in the thermal oxidation process of fats.