Characterization of sterols in refined borage oil by GC‐MS

Borage oil sterols were isolated by TLC and characterized using GC and GC‐MS. Several diunsaturated Δ 5 ‐sterols, some of them not previously recorded in vegetable oils, were found. Of these, 24‐methylcholesta‐5,23‐dienol and 24‐ethylcholesta‐5,23‐dienol could be useful markers for borage oil. Two other diunsaturated Δ 5 ‐sterols that are rarely found in vegetable oils, 24‐methylcholesta‐5,24(25)‐dienol and 24‐ethylcholesta‐5,24(25)‐dienol, were identified. The diunsaturated C‐24(28)‐sterol, isofucosterol, was also found, as well as the monounsaturated Δ 5 ‐sterols campesterol and sitosterol. These are normally present in vegetable oils, which makes them unsuitable as markers for borage oil.