GC/MS and 1H-NMR Analysis of Phytanic Acid Synthesized from Natural trans-Phytol and a Synthetic Phytol Standard

Phytanic acid (3,7,11,15-tetramethylhexadecanoic acid) is a bioactive multi-branched fatty acid mainly synthesized by ruminants from trans-phytol which is found esterified in chlorophyll. Many clinical and biochemical studies were carried out with phytol and phytanic acid, but the stereochemistry of both compounds has not been detailed in either case. In this study, we released trans-phytol from a sample of fresh grass and isolated the natural product from the unsaponifiable matter by means of high-speed counter-current chromatography (HSCCC). The trans-phytol obtained by this measure was used as starting material for the synthesis of phytanic acid. The starting material and the products of this synthesis were compared to the compounds generated in parallel from commercial phytol labeled as “cis-/trans-mixture”. While the phytanic acid produced from trans-phytol from the grass sample was enantiopure on C-7 and C-11, the commercial phytol standard proved to be racemic. These differences could be elaborated by means of the trimethylsilylether of phytol and the methyl esters of phytanic acid. Likewise, ¹H-NMR of phytanic acid methyl ester was suitable to distinguish the natural 3R,7R,11R-/3S,7R,11R-diastereomers from all racemic 3RS,7RS,11RS-phytanic acid by means of the signal dispersion of the multiplets at ~2.1 and ~2.3 ppm. Our results indicate that racemic phytol has been used in different chemical, analytical and biochemical studies. Due to the extraordinary relevance of stereoisomerism, future studies should take advantage of the natural products, i.e. trans-phytol and phytanic acid, with R-configuration on C-7 and C-11. Moreover, the specific composition of the compounds used in studies should be addressed in future studies.