Conditions suitable for preparative isolation, quantitative separation and determination ofplastochromanol-8 (PC-8), and their mild oxidation products were elaborated. Mild oxidation of PC-8 alone and with gammatocopherol (gamma-T) equimolare mixture by benzoquinone gives four and two new products, respectively. These products give Emmerie-Engel reaction. Four of gamma-T, three of PC-8 and two mixed mild oxidation products were found in linseed (Leu number = 49). It was also found that PC-8 derived from plant oils was a natural antioxidant better inhibiting autoxidationthan alpha-tocopherol in the model system in which lard was the substrate.

Among the most important metabolic compounds there are some which are not synthesized by human and animal organisms and have to be supplied in appropriate quantities in due time. Vitamin E and the essential unsaturated fatty acids have crucial physiological significance, and their greatest quantities occur in plant oils. During refining, apart from unnecessary substances, nutritionally advantageous compounds are also being eliminated. In the present paper changes of tocochromanols taking place during refining of rapeseed oil obtained from seeds of two subsequent crops were investigated. It was observed that losses of tocopherols exceeded 30%, two thirds of which resulted from distilling off during deodorization. The ratio of vitamin E to essential unsaturated fatty acids expressed as the Harris coefficient decreased in the refined oil obtained from seeds of two subsequent crops by about 28%.

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0.02 M . B u c h o w s k i , Malgorzata N o g a l a -K a l u c k a a n d M . G o g o l e w s k i *Rapeseed oilcrude and refinedand the fraction of acylglycerols isolated from these oils were added to natural amounts of tocopherols or phospholipids and were heated in conditions similar to fritting during 30 hours. Maximum formation of dimers amounted to 24% of initial quantity of tocopherols. In the samples heated at 170°C dimers occurred incidentally, only in model systems of acylglycerols with addition of tocopherols and mainly with big concentration of alphatocopherol. Also the accelerating influence of natural oil components on tocopherol decrease at 1700C was observed. I n t r o d u c t i o nProperties of tocopherols as major antioxidants are synergetically increased by phospholipids. Radicals and further onperoxides originated during autoxidation of fats cause either formation of tocopherol radicals which according to Skinner' are the forerunners of their di-and trimerization, or their destruction. It was proved that dimers of tocopherols possess reduction properties and can be determined by the Emmerie-Engel method', and that at 45°C they are antioxidants for lard acylglycer-The research aimed at the investigation of qualitative and quantitative changes of tocopherols and phospholipids taking place during long-lasting heating at the temperature of fritting with simultaneous passage of water vapour. The model systems were heated supposed to eliminate the mutual influence of phospholipids and tocopherols, composed of the acylglycerols derived from the oil with addition of native phospholipids and tocopherols in quantities to be found in oil, as well as the crude and refined rapeseed oils. 01s~.M a t e r i a l s a n d M e t h o d s Crude and refined rapeseed oils sampled directly from the processing line were used for investigation. The glyceride fraction was obtained from the refined oil by crystallization from the acetone solution (1:lO v/v) -70°C. It was purified on a column filled with the activated (3h, 300°C) A1203 following the Brockmann 111; the solventhexane -was evaporated in Nz.Phospholipids were obtained from the crude rapeseed oil following the technique described by Bratkowska4.Individual fractions were separated using TLC. The plates coated with gel -MN-Kieselgel G were developed unidirectionally with the developing mixture chloroform -methanol (2:l v/v)'. h d e m n g e n der Tocopherole und Phosphollpide wahrend der Erhitzena von Rapsol mit niedrigem Erucasauregehalt bei einer Tempemtur, dle dem Braten entspricht Rohes und raffiniertes Raps61 und daraus erhaltene Triglyceride wurden unter Zugabe von Tocopherolen und Phospholipiden 30 Stunden unter Bedingungen erhitzt. die dem Braten entsprechen. Der maximale Gehalt an entstandenen Dimeren betrug 24 % der zugegebenen Menge anToqopherolen. In den auf 170°C erhitzten Probc .n traten die Dimeren sporadisch nur bei den Modellsystemen der Triglyceride mit Zusatz von Tocopherolen auf und dann hauptsrchlich bei hoher Konzentration an alpha-Tocopherol. ...