Oxidative Dimerization of Tocopherols in Saturated and Unsaturated Triglycerides. III Formation of 5-(ƒÂ-Tocopheroxy)-ƒÂ-5-tocopherol and 5-(ƒÂ-Tocoph

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1 Oxidative Dimerization of Tocopherols in Saturated and Unsaturated Triglycerides. III Formation of 5-(ƒÂ-Tocopheroxy)-ƒÂ-5-tocopherol and 5-(ƒÂ-Tocopherol-5-yl)-ƒÂ-tocopherol from ƒâ-tocopherol Tsuyoshi FUJITANI and Hisako ANDO Fukuyama Branch School, Faculty of Education, Hiroshima University (2-17, Midorimachi, Fukuyama) d-ƒâ-tocopherol (ƒâ-toc), which was dissolved in saturated and unsaturated trigiycerides, was oxidized with air under the condition of thermal oxidation. Experimental conditions and analytical methods were the same as those described in Parts I and II of this series. From the results of TLC and HPLC of the nonsaponifiable material obtained from the reaction mixture, it was assumed that the dimers of ƒâ-toc may be formed (Figs.-1 and 2). In order to confirm oxidative dimerization, the reaction mixture, which was obtained by the oxidation in trilaurin at 180 Ž for 5 h, was separated by chromatography on a silicic acid column eluted with hexane-ethyl ether mixtures, and three main oxidation products were isolated (Fig.-4). Product [ I ] was identified as 5-(ƒÂ-tocopheroxy)-ƒÂ-(toco pherol (ƒâ-ted), and both products [II] and [Ill] were identified as 5-(ƒÂ-tocopherol-5-yl)-ƒÂ-tocopherol (ƒâ-tbd) by means of UV absorption, IR absorption, NMR and MS spectrometry (Table-1). Product [III] seems to be the atropisomer of product [II]. The decrease of ƒâ-toc concentration and the formation of the dimers during the course of thermal oxidation in trilaurin (Tri-La), in triolein (Tri-Ol), and in trilinolein (Tri-Li) were followed by HPLC. The decomposition of ƒâ-toc in Tri-Li was more rapid than that in Tri-La (Fig.-5). ƒâ-ted was formed more abundantly than ƒâ-tbd. The quantities of the formed dimers were greatly affected by the species of triglyceride molecules, and large amounts of dimers were obtained by the oxidation in Tri-Li. The amount of ƒâ-tbd obtained by oxidation in Tri-Li reached a maximum within 5 h, and the quantity of this dimer formed by the oxidation at 150 Ž is much larger than that at 180 Ž (Figs.-6 and 7).

2 Sample : Ii Reaction mixture I oxidized in trilaurin).21 Reaction mixture oxidized ix trilinolein 3~ Authentic ii Toe 4~ Authentic it TED 51 Authentic is-tbd`h} 6) Authentic d-tbd Lj Plate : Kieselgel HF 254, 0.25 mm Solvent : Hexane Ethyl ether 70:30 Fig. 1 TLC separation of reaction mixture after oxidation of d-o-tocopherol with air in trilaurin and in trilinolein at 180t, for

3 (A] EL (C) Sample : [A] Reaction mixture (oxidized in trilaurin) [B] Reaction mixture (oxidized in trilinolein) [C] Reaction mixture (oxidized in trilaurin) (Quantity of sample of this chromatogram is about ten times that of chromatogram [A] ) Operating conditions : Instrument : Hitachi 635 High speed liquid chromatograph Column packing : Hitachigel $$ 3040, 2,I'(500 mm Detector : UV photometer, 295 nm Mobile phase : Hexane-Diisopropyl ether 90: 10 Flow rate :1.0 ml/min Fig.-2 High-performance liquid chromatograms of oxidized d-o--tocopherol, Fig.-3 Structure of starting material and oxidation products.

4 Fig. -5 Change in d-o-tocopherol concentration during the course of thermal oxidation in saturated and in unsaturated triglyce= rides. H : Hexane, E : Ethyl ether c1-u-tocopherol was oxidized with air in trilaurin at 180 C for. Nonsaponif iable material(0.878g) obtained from the reaction mixture was applied on a silicic acid column and was eluted from the column with hexane ethyl ether mixiures. Fig.-4 Chromatographic separation of oxidized cl ci-tocopherol. Fig.-6 Change in 3-TED content during the course of thermal oxidation of d-otocopherol in saturated and in un= saturated triglycerides. Table 1 Properties of the dimers separated from the oxidation products of d-o-tocopherol.

5 20 1 isomer f, isomer Tri La. 180(.' Tri-La, 1500 Tri-0l. Tri-Li, 180'C 180'C Tri Li, 150`C Fig.-7 Changes in 5-TBD (K) and 5 TBD (L) contents during the course of thermal oxidation of d-s-tocopherol in saturated and in unsaturated triglycerides. Fig. 8 Change in carbonyl value of triglycerides during the course of thermal oxidation.

6 1) J. L. G. Nilsson, Chem. Scand., G. D. Daves 22, 297 (1968) Jr., K. Folkers, Acta 2) T. Nakamura, S. Kijima, Chem. Pharm. Bull., 20, 1297 (1972) 3) Y. Ishikawa, E. Yuki, Agr. Biol. Chem., 39, 851 (1975) 4) Y. Ishikawa, E. Yuki, H. Kato, M. Fujimaki, Agr. Biol. Chem., 42, 703 (1978) 6) E. Yuki, K. Morimoto, Y. Ishikawa, H. Noguchi, 11) J. Lehmann, H.T. Slaver, Lipids, 11, 853 (1976) 12) J. L. G. Nilsson, H. Sievertsson, Acta Chem. Stand., 23, 859 (1969)

alternating current component and two transient components. Both transient components are direct currents at starting of the motor and are sinusoidal

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