Antimicrobial activity profiles of the two enantiomers of limonene and carvone isolated from the oils of Mentha spicata and Anethum sowa

Abstract

The antimicrobial activity of the essential oils of Mentha spicata L. and Anethum sowa Roxb. (Indian dill) were studied. The major chemical constituents of the hydrodistilled essential oils and their major isolates from cultivated M. spicata and A. sowa were identified by IR, 1H- and ¹³C-NMR and GC: (S)-(-)-limonene (27.3%) and (S)-(-)-carvone (56.6%) (representing 83.9% of the spearmint oil) and (R)-(+)-limonene (21.4%), dihydrocarvone (5.0%), (R)-(+)-carvone (50.4%) and dillapiole (17.7%) (together 76.9% in Indian dill oil), respectively. In vitro bioactivity evaluation of the isolated oil components revealed that both the optical isomers of carvone were active against a wide spectrum of human pathogenic fungi and bacteria tested. (R)-(+)-limonene showed comparable bioactivity profile over the (S)-(-)-isomer. The activity of these monoterpene enantiomers was found to be comparable to the bioactivity of the oils in which they occurred.