Comprehensive investigation of tocochromanols (vitamin E compounds) in vegetable oils and food supplements

Beschreibung

Tocochromanols are among the most important naturally occurring lipophilic antioxidants in plants and animals, including humans. The group of tocochromanols includes some twenty structurally closely related compounds. Depending on the methylation pattern on the aromatic part of the obligate 6-chromanol ring, α-, β-, γ-, and δ-homologues are distinguished. The number of double bonds in the isoprenoid side chain with sixteen carbon atoms additionally allows to classify tocopherols, tocomonoenols, tocodienols and tocotrienols. However, most data on tocochromanols in food is restricted to tocopherols and partly tocotrienols while data on tocomonoenols and tocodienols hardly exist. The objective of the present doctoral thesis was the development of comprehensive and fast determination methods of tocochromanols in food samples and dietary supplements with special focus on tocomonoenols and tocodienols. This included a quantitative instrumental thin-layer chromatography (TLC) method for the fast determination of tocochromanols in dietary supplement capsules. Also, a special focus was put on the quantitative analysis of tocomonoenols and other minor tocochromanols in edible plant oils. For this purpose, additional reference standards were required. In a first step, it was aimed to isolate γ-tocomonoenol from pumpkin seed oil by countercurrent chromatography (CCC). In order to obtain the required separation power and sensitivity for tocomonoenols and tocodienols, the determination was based on gas chromatography coupled with mass spectrometry (GC/MS) after trimethylsilylation. This approach also required the development of a suitable sample preparation method for all tocochromanols in edible plant oils and the selection of an appropriate internal standard. The final method was applied to a wide range of edible plant oils. The tocomonoenol and tocodienol findings in these oils contribute to a better understanding of the relevance of minor tocochromanols.

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Alexander Stefan Kröpfl

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Vitamin E Tocochromanol Tocomonoenol

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