Individual and joint activity of terpenoids, isolated from Calamintha nepeta extract, on Arabidopsis thaliana

Four terpenoids, camphor, pulegone, trans-caryophyllene and farnesene, previously found in Calamintha nepeta (L.) Savi methanolic extract and essential oils were assayed on germination and root growth of Arabidopsis thaliana (L.) Heynh. None of the terpenes, singularly or in combination, was able to inhibit the germination process. Farnesene and trans-caryophyllene caused a strong inhibitory effect on root growth, and pulegone, at the highest concentrations, reduced lateral root formation. Although the mixture of camphor-trans-caryophyllene with or without farnesene did not cause any effect on root growth, the addition of pulegone induced a marked synergistic activity. Moreover, the addition, at low concentration, of farnesene to pulegone-camphor-trans-caryophyllene mixture further increased the inhibitory effect on root elongation. These results suggested that the inhibitory effects caused by C. nepeta methanolic extract may depend on the combined action of different molecules.