Identification of the novel odor active compounds "p-menthane lactones" responsible for the characteristic aroma of fresh peppermint leaf

The comparative aroma extract dilution analysis (cAEDA) applied to the volatile fractions of two types of fresh mint leaves (Peppermint and Spearmint) revealed 20 odor-active peaks with high FD factors (>= 64). Among the perceived odorants, five "sweet/milky" and "caramel-like/spicy" notes showing high FD factors were characteristic for the peppermint aroma, and were identified as p-menthane lactone derivatives. Especially, the three p-menthane lactone derivatives, "rel-(3S,3aS,6R,7aS)-dihydromintlactone, (3S,3aS,6R)-epoxymenthofurolactone, and 2E-ethylidene-5-methylcyclohexanone", were newly identified compounds in the peppermint. The biosynthetic routes of the p-menthane lactone derivatives have been suggested to be closely related to menthofuran. Therefore, these findings strongly suggest the possibility that the biosynthetic pathway leading to the p-menthane lactone derivatives via menthofuran plays a significantly important role in the formation of the characteristic aroma of peppermint.