Identification of lignans as major components in the phenolic fraction of olive oil.
BACKGROUND
Because olive oil is an important component of the Mediterranean diet, it is necessary to establish unequivocal identification of the major potential antioxidant phenolic compounds it contains.


METHODS
The major phenolic antioxidants in extra virgin olive oil were isolated and purified. Structural analysis was conducted using several spectroscopic techniques, including mass spectrometry and nuclear magnetic resonance (NMR). In particular, detailed (1)H and (13)C NMR data are presented, and several assignment errors in the literature are corrected.


RESULTS
The data show for the first time that the lignans (+)-1-acetoxypinoresinol and (+)-pinoresinol are major components of the phenolic fraction of olive oils. These lignans, which are potent antioxidants, are absent in seed oils and virtually absent in refined virgin oils but are present at concentrations of up to 100 mg/kg (mean +/- SE, 41.53+/-3.93 mg/kg; range, 0.65-99.97 mg/kg) in extra virgin oils. As with the simple phenols and secoiridoids, there is considerable interoil variation in lignan concentrations. Foods containing high amounts of lignan precursors have been found to be protective against breast, colon, and prostate cancer.


CONCLUSIONS
Lignans, as natural components of the diet, may be important modulators of cancer chemopreventive activity.
Owen
R W
RW
Division of Toxicology and Cancer Risk Factors, Central Spectroscopy Department, German Cancer Research Center, Im Neuenheimer Feld 280, D-69120 Heidelberg, Germany. r.own@dkfzheidelberg.de
Mier
W
W
Giacosa
A
A
Hull
W E
WE
Spiegelhalder
B
B
Bartsch
H
H
D002851:Chromatography, High Pressure Liquid; D004042:Dietary Fats, Unsaturated / Q000032:analysis*; D005663:Furans / Q000032:analysis / Q000302:isolation & purification; D008401:Gas Chromatography-Mass Spectrometry; D017705:Lignans / Q000032:analysis* / Q000302:isolation & purification; D009682:Magnetic Resonance Spectroscopy; D000069463:Olive Oil; D010636:Phenols / Q000032:analysis / Q000302:isolation & purification; D010938:Plant Oils / Q000737:chemistry*
D004042:Dietary Fats, Unsaturated; D005663:Furans; D017705:Lignans; D000069463:Olive Oil; D010636:Phenols; D010938:Plant Oils; C103298:pinoresinol