Developments in the isolation and characterization of beta-damascenone precursors from apples
1995
Roberts, D.D. | Acree, T.E.
beta-Damascenone is a potent aroma compound in a variety of natural products, with a low odor threshold of 2 pg/g in water. Its characterizing presence in heated apple products is due to liberation from precursors. The isolation of beta-damascenone precursors from apples Malus domestica, Borkh. CV Empire was performed using Amberlite XAD-2 and C-18 flash chromatography followed by C-18 HPLC. At least eight separate precursors were found, and the most abundant was further characterized. Ion spray tandem mass spectrometry with its mild ionization conditions provided molecular weight and structural information. Enzymatic hydrolysis-GC/MS and trimethylsilation-GC/MS gave aglycone and sugar information on the precursor. The most abundant precursor, present at 4.6 ng/g apple (expressed as amount of beta-damascenone liberated under acid hydrolysis), was the 9(or 3)-alpha-L arabinofuranosyl-(1,6)-beta-D-glucopyranoside of the acetylenic diol. The second most abundant precursor, present at 3.1 ng/g apple, is a more polar glycoside of the acetylenic diol. Investigations into grasshopper ketone as a beta-damascenone precursor found that while it may be a biosynthetic precursor, it is not a direct precursor, producing beta-damascenone under acid hydrolysis conditions with only a 0.006% yield. A mechanistic pathway for the conversion of the acetylenic diol to beta-damascenone was proposed.
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