Structure-Fungitoxicity Relationships of the Monoterpenoids of the Essential Oils of Peppermint (<i>Mentha piperita</i>) and Scented Geranium (<i>Pelargonium graveolens</i>)

Abstract

Abstract The fungitoxicity of essential oil of peppermint (Mentha piperita) and its primary monoterpene constituents, namely menthol, neomenthol, linalool, menthyl acetate and menthone was assayed. Median effective concentrations (EC50) of these constituents for the mycelial growth inhibition of Colletotrichum gloeosporioides were determined and were compared with those of geraniol and citronellol which are the chief constituents of the oil of scented geranium (Pelargonium sp.). Structure-activity relationship studies revealed that alcoholic group is necessary for activity and that primary alcoholic group is the most potent followed by secondary alcoholic, while the tertiary alcoholic group is the least potent.