LC-MS method development to evaluate major triterpenes in skins and cuticular waxes of grape berries

Predominant triterpenes (free oleanolic acid, beta-sitosterol and beta-sitosterol-3-O-beta-d-glucoside) in skin and cuticular wax of grape berries have been analysed by liquid chromatography-mass spectrometry (LC-APCI-MS). The validity of the developed method was established by determining linearity, recovery, precision, accuracy, limit of detection and quantification. Detection limits were in the range of 0.12-0.25 mg L-1, and linearity values ranged up to 105 mg L-1. The repeatability of the method was good. High variability was found among the measured grape varieties based on triterpene content, quantitites of oleanolic acid of cuticular wax ranged from 31.53 mg kg(-1) to 162.01 mg kg(-1) of the twelve analysed samples. The highest sitosterol content was measured in the sample 'Othello' (73.12 mg kg(-1)), while maximum sitosterol glucoside content was also found in 'Othello' variety (13.68 mg kg(-1)). The results showed that the study on triterpenes could be an informative tool to characterise grape varieties.