Long-chain γ-pyrones in epicuticular wax of two Vanilla bean species:: V-fragrans and V-tahitensis

Analyses of the neutral lipids from Vanilla species before saponification resulted in the identification of a new product family in this genus: long-chain gamma-pyrone compounds with an aliphatic chain containing a cis double bond at the n-9 position. These compounds represent 7-8% of the neutral lipids in mature beans. Using NMR and gas chromatography/mass spectrometry, three gamma-pyrones have been identified, including 2-(10-nonadecenyl)-2,3-dihydro-6-methyl-4H-pyran-4-one, 2-(12-heneicosenyl)-2,3-dihydro-6-methyl-4H-pyran-4-one and 2-(14-tricosenyl)-2,3-dihydro-6-methyl-4H-pyran-4-one. The major constituent was 2-(14-tricosenyl)-2,3-dihydro-6-methyl-4H-pyran-4-one, which represented 70.3% of the gamma-pyrone fraction. The variability of this compound family has been studied in relation to bean maturity in V. fragrans and V. tahitensis beans. This compound family has not been found either in leaves or in stems or in V. madagascariensis beans.