4-Demethylsterols and triterpene alcohols from two Vanilla bean species: Vanilla fragrans and V. tahitensis

Abstract

4-Demethylsterol and triterpene alcohol compositions of two Vanilla bean species (V. fragrans and V. tahitensis) were investigated. From retention times and gas chromatography-mass spectrometry, nine 4-demethylsterols were identified in V. fragrans and seven in V. tahitensis. The 4-demethylsterol fraction of V. fragrans was characterized by a high content of 24-methylene cholesterol (27–40%) and of β-sitosterol (35–46%). The 4-demethylsterol fraction of V. tahitensis was characterized by a high content of stigmasterol (27%) and of β-sitosterol (57.5%), and a lower amount of 24-methylene cholesterol (5%). Vanilla tahitensis was also characterized by the presence of ergosta-5,25-dien-3β-ol (2%) and the absence of campesterol, stigmasta-5,22,25-trien-3β-ol, and ergosta-7,24(28)-dien-3β-ol. The beans’ age modified the ratio 24-methylene cholesterol/β-sitosterol in V. fragrans. Combining liquid chromatography and gas chromatography allowed the identification of four other demethylsterols in V. fragrans (brassicasterol, 0.02%; stigmasta-5,23-dien-3β-ol, 1.43%; stigmasten-22-ol, 0.1%; and fucosterol, 0.5%) from the 4-demethylsterol fraction. 24-Methylene cholesterol and β-sitosterol were isolated, and their structures were confirmed by ¹H and ¹³C nuclear magnetic resonance. Four triterpene alcohols were identified in V. fragrans, including cycloartenol (0.9–1.6%) from the triterpene alcohol fraction, 24-dihydrotirucallol (17–23%) from the triterpene alcohol fraction, tirucall-7-en-3β-ol (6–7.5%) from the triterpene alcohol fraction, and in a higher content cyclosadol (66–69%) from the triterpene alcohol fraction. The content ranges were studied as a function of the beans’ age. Demethylsterol and triterpene alcohols profile could be used for origin differentiation.