New Terpenic Alcohols in Essential Oil of Mentha gentilis L. Containning (+)-Pulegone as a Main Component

Abstract

We attempted to investigate the essential oil of “Seto-mint” (one of Mentha gentilis L. grown in Tokai area) which contains (+)-pulegone as a main component.
In this paper, we wish to inform the confirmation of the following new terpenic alcohols isolated from the essential oil; (-)-(1 R:3 R)-3-hydroxy-4 (8)-p-menthene (2), (+)-1 R-8-hydroxy-3-p-menthene (3) and (-)-1 R-8-hydroxy-4-p-menthen-3-one (4).
The contents of these constituents of the essential oil in this plant have been found seasonally variable and biosynthetic processes in vivo were shown as Scheme 1. It seems that (+)-1 R-pulegone (1) is reduced to afford 2. This yields 3 on isomerization with a minor organic acid in the plant, while 4 as one of the above related substances may also be derived from 1.