Levels of pyrroloquinoline quinone in various foods
The levels of free pyrroloquinoline quinone (PQQ) in various foods were examined by the use of gas chromatography-mass spectrometry. PQQ was extracted from the samples, after addition of [U-13C]PQQ as internal standard, with n-butanol and Sep-Pak C18 cartridges. After derivatization of PQQ with phenyltrimethylammonium hydroxide, molecular peaks at m/z 448 and 462 were used for detection of PQQ and [U-13C]PQQ respectively, by selected ion monitoring. Free PQQ could be detected in every sample in the range 3.7-61 ng/g or ng/ml. Since its levels in human tissues and body fluids are 5-10 times lower than those found in foods, it is probable that PQQ existing in human tissues is derived, at least partly, from the diet.
Levels of pyrroloquinoline quinone in various foods Biochem J. 1995 April