Menthyl isovalerate

Menthyl isovalerate, also known as validolum, is the menthyl ester of isovaleric acid. It is a transparent oily, colorless liquid with a smell of menthol. It is very slightly soluble in ethanol, while practically insoluble in water. It is used as a food additive for flavor and fragrance.

Validol, the anxiety medication containing a roughly 25% solution of menthol in menthyl isovalerate is prepared essentially in one step, in which the amount of menthol added before conducting the acid catalysed esterification is in an excess such that the resulting solution of the yielded ester has around 25% menthol, simplifying the procedure. Work up might consist of several washings, including one with aqueous sodium bicarbonate to neutralize traces of acid catalyst and unreacted isovaleric acid, and distillation.

Medical use
In Poland, Bulgaria, Romania and the former Soviet Union states including Russia, menthyl isovalerate mixed with roughly 25% menthol is sold as an anxiolytic under various trade names including Extravalerianic, Validol, Valofin, and Menthoval.