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Porphyria cutanea tarda (PCT) is commonly diagnosed in cases where multiple hyperechoic nodules are observed in the liver. Pathologically, these nodules associated with PCT are focal fatty deposits. We report here, seven cases of PCT with fatty changes over multiple foci in the liver. Furthermore, the characteristics of ultrasonography (US) findings of 32 previously reported cases are summarized. The US features of these nodules showed a homogenous hyperechoic or hyperechoic rim pattern, partial confluence, and no mass effect in the vascular structures. Because multiple hyperechoic liver nodules occasionally mimic malignancies, and because their diagnosis can be challenging, clinicians should consider checking urine porphyrin levels to rule out PCT when such nodules are observed on US., (© 2021 Wiley Periodicals LLC.)

A sensitive HPLC procedure with postcolumn reduction and electrochemical detection was developed for the analysis of vitamin E and its oxidation products, alpha-tocopherylquinone, epoxy-alpha-tocopherylquinones, and 8a-(lipid-dioxy)-alpha-tocopherones. After the separation on a reversed-phase column, on-line zinc-catalyzed reduction allowed the detection of alpha-tocopherylquinone and epoxy-alpha-tocopheryl-quinones, whereas platinum-catalyzed reduction allowed the detection of 8a-(lipid-dioxy)-alpha-tocopherones. The lowest detectable level of each compound was about 0.2 pmol at the signal-to-noise ratio of 3. This method was applied to the detection of alpha-tocopherol products in peroxidized human plasma. When the plasma was peroxidized by the addition of a free radical initiator, peaks corresponding to alpha-tocopherylquinone, epoxy-alpha-tocopherylquinones, and the addition products of alpha-tocopherol with peroxyl radicals derived from cholesteryl ester hydroperoxides and PC hydroperoxides were observed. The amount of these oxidation products in the plasma increased with the depletion of endogenous alpha-tocopherol. The results indicate that the method is useful to detect the oxidation products formed by the peroxyl radical-trapping reactions of alpha-tocopherol in biological systems.

A chemiluminescence-based high-performance liquid chromatographic method was developed for the analysis of the addition products of alpha-tocopherol with phosphatidylcholine-peroxyl radicals (TOO-PC). The TOO-PC eluted from a reversed-phase column was reacted with a chemiluminescent reagent consisting of a Cypridina luciferin analog and a lipid-soluble iron chelate in acidic methanol at 50 degrees C, and the generated chemiluminescence was monitored. The detection limit for TOO-PC by this method was about 1 pmol. This method was applied to the detection of TOO-PC in the peroxidized membranes prepared from rabbit erythrocyte ghosts. When the erythrocyte ghosts were peroxidized by the addition of a water-soluble free radical initiator, a peak corresponding to TOO-PC was detected on the chromatogram with chemiluminescent detection. The amount of TOO-PC in the erythrocyte membranes increased with the depletion of endogenous alpha-tocopherol. The results indicate that this method proved useful for the detection of the TOO-PC formed by the peroxyl-radical scavenging reactions of alpha-tocopherol in biological systems.

alpha-Tocopherol and methyl (9Z,11E)-(S)-13-hydroperoxy-9,11-octadecadienoate (13-MeLOOH) were allowed to stand at 100 degrees C in bulk phase. The products were isolated and identified as methyl 13-hydroxyoctadecadienoate (1), stereoisomers of methyl 9,11,13-octadecatrienoate (2), methyl 13-oxo-9,11-octadecadienoate (3), epoxy dimers of methyl linoleate with an ether bond (4), a mixture of methyl (E)-12,13-epoxy-9-(alpha-tocopheroxy)-10-octadecenoates and methyl (E)-12,13-epoxy-11-(alpha-tocopheroxy)-9-octadecenoates (5), a mixture of methyl 9-(alpha-tocopheroxy)-10,12-octadecadienoates and methyl 13-(alpha-tocopheroxy)-9,11-octadecadienoates (6), alpha-tocopherol spirodiene dimer (7), and alpha-tocopherol trimer (8). alpha-Tocopherol and 13-MeLOOH were dissolved in methyl myristate, and the thermal decomposition rate and the distributions of reaction products formed from alpha-tocopherol and 13-MeLOOH were analyzed. alpha-Tocopherol disappeared during the first 20 min, and the main products of alpha-tocopherol were 5 and 6 with the accumulation of 1-4 which were the products of 13-MeLOOH. The results indicate that the alkyl and alkoxyl radicals from the thermal decomposition of 13-MeLOOH could be trapped by alpha-tocopherol to produce 5 and 6. The reaction products of alpha-tocopherol during the thermal oxidation of methyl linoleate were compounds 6 and 7. Since the radical flux during the autoxidation might be low, the excess alpha-tocopheroxyl radical reacted with each other to form 7.

A novel derivative of vitamin E, vitamin E glucoside, was synthesized from 2-hydroxymethyl-2,5,7,8-tetramethylchroman-6-ol and maltose in a solution containing DMSO by transglycosylation with alpha-glucosidase from Saccharomyces species. The glycosylated product was identified as 2-(alpha-D-glucopyranosyl)methyl-2,5,7,8-tetramethylchroman-6-ol (TMG) by mass spectrometry and nuclear magnetic resonance spectroscopy. The optimal pH of transglycosylation was 5.5, and the yield of TMG increased as the concentration of maltose increased. TMG has high solubility in water (> 1 x 10(3) mg/mL). The 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity of TMG was found to be nearly the same as those of alpha-tocopherol, Trolox (2-carboxy-2,5,7,8-tetramethylchroman-6-ol), and ascorbic acid.

alpha-Tocopherol was reacted with methyl 13(S)-hydroperoxy-9(Z), 11(E)-octadecadienoate in the presence of an iron-chelate, Fe(III)-acetylacetonate, at 37 degrees C in benzene. The reaction was carried out either aerobically or anaerobically. The main products of alpha-tocopherol under air were isolated and identified as two stereoisomers of 4a,5-epoxy-8a-hydroperoxy-alpha-tocopherone, four stereoisomers of methyl 9-(8a-dioxy-alpha-tocopherone)-12, 13-epoxy-10(E)-octadecenoate, four stereoisomers of methyl 11-(8a-dioxy-alpha-tocopherone)-12,13-epoxy-9(Z)-octadecenoa te, two stereoisomers of methyl 13(S)-(8a-dioxy-alpha- tocopherone)-9(Z),11(E)-octadecadienoate, and alpha-tocopherol dimer. Besides the 8a-(lipid-peroxy)-alpha-tocopherones, two stereoisomers of methyl 11-(alpha-tocopheroxy)-12(S),13(S)-epoxy- 9(E)-octadecenoate, two stereoisomers of methyl 9-(alpha-tocopheroxy)-12(S), 13(S)-epoxy-10(E)-octadecenoate, and two isomers of methyl (alpha-tocopheroxy)-octadecadienoate were obtained under nitrogen atmosphere. The results indicate that the peroxyl radicals from lipid hydroperoxides prefer to react with the 8a-carbon radical of alpha-tocopherol and the carbon-centered radicals react with the phenoxyl radical of alpha-tocopherol.

alpha-Tocopherol was reacted with alkyl and alkylperoxyl radicals at 37 degrees C in bulk phase. The lipid-free radicals were generated by the reaction of methyl linoleate with the free radical initiator, 2,2'-azobis(2,4-dimethylvaleronitrile) (AMVN) under air-insufficient conditions. The products were isolated by high-performance liquid chromatography. Their structures were identified as 2-(alpha-tocopheroxy)-2,4- dimethylvaleronitrile (1), a mixture of methyl 9-(8a-peroxy-alpha-tocppherone)-10(E),12(Z)-octadecadienoate and methyl 13-(8a-peroxy-alpha-tocopherone)-9(Z),11(E)-octadecadienoate (2), methyl 9-(alpha-tocopheroxy)-10(E),12(Z)-octadecadienoate (3a), methyl 13-(alpha-tocopheroxy)-9(Z),12(E)-octadecadienoate (3b), alpha-tocopherol spirodiene dimer (4) and alpha-tocopherol trimer (5). When methyl linoleate containing alpha-tocopherol was oxidized with AMVN under air-sufficient conditions, the main products were 8a-alkylperoxy-alpha-tocopherones (2). In addition to these compounds, 6-O-alkyl-alpha-tocopherols (1, 3a and 3b) were formed when the reaction was carried out under air-insufficient conditions. The results indicate that alpha-tocopherol can react with both alkyl and alkylperoxyl radicals during the autoxidation of polyunsaturated lipids.

alpha-Tocopherol was reacted with an alkylperoxyl radical at 37 degrees C in ethanol. 2,2'-Azobis(2,4-dimethylvaleronitrile) was used to generate the alkylperoxyl radicals. The reaction products of alpha-tocopherol were isolated by reverse-phase and normal-phase high performance liquid chromatography, and their structures were characterized by infrared, ultraviolet, 1H and 13C nuclear magnetic resonances and mass spectrometry. They were 8aS-hydroperoxy-alpha-tocopherone, 8aR-hydroperoxy-alpha-tocopherone, a mixture of 7,8-epoxy-8aS-ethoxy-alpha-tocopherone and 7,8-epoxy-8aR-ethoxy-alpha-tocopherone, 8aS-(1R-cyano-1,3-dimethyl)butylperoxy-alpha-tocopherone+ ++, 8aS-(1S-cyano-1,3-dimethyl)butylperoxy-alpha-tocopherone+ ++, a mixture of 8aR-(1R-cyano-1,3-dimethyl)butylperoxy-alpha-tocopherone+ ++ and 8aR-(1S-cyano-1,3-dimethyl)butyl-peroxy-alpha-tocopherone, 4aS,5R-epoxy-8aR-ethoxy-alpha-tocopherone, 4aR,5S-epoxy-8aS-ethoxy-alpha-tocopherone, 4aS,5R-epoxy-8aS-ethoxy-alpha-tocopherone and 4aR,5S-epoxy-8aR-ethoxy-alpha-tocopherone.

The reaction products of alpha-tocopherol and its model compound, 2,2,5,7,8-pentamethylchroman-6-ol, during the autoxidation of methyl linoleate at 37 C were investigated. Two isomeric trimers were obtained as the major reaction products of alpha-tocopherol, and a trimer was obtained as that of its model chroman. The structure of each trimer has been characterized by IR, UV, 1H and 13C NMR, and mass spectroscopy. The 13C NMR spectra showed the presence of a quaternary carbon atom and a carbon atom bearing two oxy substituents in the molecule. On methanolysis of each trimer, equimolar amounts of the 5-methoxymethyl compound and the dihydroxy dimer were formed, indicating the presence of a ketal group in the molecule. From these results, new trimeric structures are proposed. The reaction products of alpha-tocopherol could be well-separated by reverse-phase high performance liquid chromatography. When methyl linoleate was autoxidized in the presence of 1 mol% alpha-tocopherol, spirodiene dimer was the initial reaction product of alpha-tocopherol, and trimers were formed with the decrease of alpha-tocopherol.