Phytoxic activity and GC-MS chemical characterization of apple mint foliar volatiles and essential oils

Foliar volatiles and essential oils produced by apple mint [Mentha rotundifolia auct. non (L.) Huds.], a widely distributed Mediterranean species, were investigated for their phytotoxic activities on seed germination and/or root growth of the sensitive test species Lactuca sativa and four of the most common weeds largely found in several agro-ecosystems (Amaranthus retroflexus, Chenopodium album, Echinochloa crusgalli and Eleusine indica). The results pointed out that foliar volatiles (VOCs) were characterized by a high inhibitory effect on both germination and root growth of lettuce. Moreover, apple mint essential oils, extracted from fresh material through steam distillation, were characterized by a high phytotoxicity on weeds germination and root growth. The chemical characterization of the essential oils, carried out through GC-MS, highlighted that monoterpenes were the main chemicals followed by sesquiterpenes. Interestingly, the most abundant compounds were α-pinene, β-pinene and limonene, which are largely known to be strong phytotoxic allelochemicals.