LC-Orbitrap-HRMS Determination of Two Novel Plastochromanol Homologues

The antioxidant plastochromanol-8 (PC-8) is a tocochromanol which differs from γ-tocotrienol in having an unsaturated side chain of eight instead of three isoprene units. The recent isolation of PC-8 from flaxseed oil indicates the additional presence of lower shares of two previously unknown homologues, plastochromanol-7 (PC-7) and plastochromanol-9 (PC-9), which feature seven and nine isoprenoid units respectively on the γ-chromanol backbone. Here, a fast LC-Orbitrap-HRMS method is applied for the determination of PC-7 and PC-9 in seven plant oils and a plant extract.

The presence of PC-7, PC-8, and PC-9 is confirmed in all eight investigated samples by LC-Orbitrap-HRMS analysis after saponification. PC-8 amounts of ≈315-350 mg kg^-1 in two flaxseed oils, ≈75 mg kg^-1 in rapeseed oil, ≈38 mg kg^-1 in camelina oil, ≈80-120 mg kg^-1 in two mustard oils, ≈90 mg kg^-1 in candle nut oil, and ≈900 mg kg^-1 dry weight in Cecropia leaves are determined by quantification. Semi-quantification of PC-7 and PC-9 indicated the presence of ≈0.1-1% of PC-7 and PC-9 in varied relative ratios.

The novel plastochromanol homologues are of particular interest to researchers with focus on vitamin E and other tocochromanols because of their unexplored bioactivity.