Isolation of the four methyl jasmonate stereoisomers and their effects on selected chiral volatile compounds in red raspberries.

The four stereoisomers present in a commercial sample of methyl jasmonate (MJ) were isolated at semi-preparative scale by HPLC, using a permethylated β-cyclodextrin column. This allowed the baseline resolution and collection of both major (methyl jasmonates) and minor (epi-methyl jasmonates) stereoisomers. When 1.5 mL of a 5mg per mL MJ solution were injected, isolated amounts were 3.56 mg for (-) and (+)-methyl jasmonates, with respective purities of 96.1% and 99.9%, and 0.18 mg for (-)- and (+)-epi-methyl jasmonates, with 98.6% and 91.6% respective purities. The post-harvest treatment of red raspberry fruits with the pure methyl jasmonate stereoisomers isolated proved that (-)-epi-MJ either promotes the bioformation of (+)-limonene or inhibits that of (-)-limonene to a greater extent than the other three MJ stereoisomers, while the biosynthesis of the (+)-enantiomer of α-ionone is favoured equally, whichever MJ stereoisomer used. The results obtained in the present study might be used to obtain food products with improved sensory characteristics.