Identification of Petroselinic Acid (Cis-6-octadecenoic Acid) in the Seed Oils of Some of the Family Umbelliferae (Panax schinseng, Aralia continentalis and Acanthopanax sessiliflorus) by GC-MS, IR, ^1H-and^13C-NMR Spectroscopic Techniques

Identification of Petroselinic Acid (Cis-6-octadecenoic Acid) in the Seed Oils of Some of the Family Umbelliferae (Panax schinseng, Aralia continentalis and Acanthopanax sessiliflorus) by GC-MS, IR, ^1H-and^13C-NMR Spectroscopic Techniques

Fatty acid compositions of the seed oils of P. schinseng, A. continentalis and A. sessiliflorus, were analyzed by gas chromatography (GC) equipped with a capillary column. A large unusual peak was observed just before the peak corresponding to oleic acid (cis-9-C_{18:1}). This unknown fatty acid was isolated by silver ion chromatography and then derivatized into the picolinyl ester. The mass spectrum of the picolinyl ester showed molecular ion at m/z=373 with other diagnostic ions such as m/z=178, 218, 232, 246, 274, 288, 302 and 344. Characteristic absorption peaks at 720;cm^{-1}, 1640;cm^{-1} and 3010;cm^{-1} in IR spectrum indicated the presence of cis-configurational double bond in the molecule. The ^1H-NMR spectrum of this acid gave two quintets centered at {delta}1.638 (2H, C-3) and {delta}1.377 (2H, C-4), and two multiplets centered at {delta}2.022{sim}2.047 (2H, C-5) and {delta}2.000{sim}2.022 (2H, C-8), and multiplet signals of olefinic protons centered at {delta}5.3015{sim}5.3426 (C-6, J=9.5 Hz) and {delta};5.3465{sim}5.3877 (C-7, J=9.5 Hz). The ^13C-NMR spectrum showed 18 carbon resonance signals including an overlapped signal at {delta}29.7002 for C-12 and {delta}29.6520 for C-13 (or they can be reversed), and other highly resolved signals at {delta}33.950, {delta}24.558, {delta}26.773 and {delta}27.205 due to C-2, C-3, C-5 and C-8 of a {Delta}^6-octadecenoic acid, respectively. From analysis results this unknown fatty acid could be identified as cis-6-octadecenoic acid. The seed oils of P. schinseng and A. sessiliflorus contained petroselinic acid (59.7%, 56.0%), oleic acid (18.3%, 6.1%) and linoleic acid (16.2%, 30.4%) with small amount of palmitic acid (3.0%, 3.1%) while the seed oil of A. continentalis comprised mainly oleic acid (30.2%), petroselinic acid (29.0%), linoleic acid (24.1%) and palmitic acid (13.1%).