Countercurrent chromatographic isolation of 11´-γ-tocomonoenol from and
detection of novel minor tocochromanols in pumpkin seed oil
Abstract
A non-refined, organic pumpkin seed oil (PSO) was chosen for the
isolation and structure verification of the rare vitamin E compound
γ-tocomonoenol (γ-T1). Initial measurements indicated the presence of
~0.4 mg γ-T1 per 100 g pumpkin seed oil. Saponification
of ~2 L pumpkin seed oil, followed by repeated
countercurrent chromatography (CCC) with the solvent system
n-hexane/benzotrifluoride/acetonitrile (10:3.5:6.5,
v/v/v) and silica gel column chromatography enabled
the isolation of 6.8 mg γ-T1 with a purity of 96.0%. Structural
analysis by 1H NMR spectroscopy and gas chromatography
with mass spectrometry (GC/MS) of the γ-T1 isolate confirmed the
presence of a double bond in C-11´-position (11´-γ-tocomonoenol). Next
to γ-T1, CCC fractionation enabled the detection of 18 different
tocochromanols, many of which were reported for the first time in
pumpkin seed oil. This unmatched variety covered among others
α-/γ-tocopherol, α-/γ-tocomonoenol, two α- and two γ-tocodienol isomers,
α-/γ-tocotrienol as well as the rare 11´-β-tocomonoenol (β-T1) and δ-T1.
Three uncommon tocochromanols were also detected whose origins and
structure remained unclear.