Effects of planting time and mineral fertilization on peppermint (<i>mentha x piperita</i> l.) essential oil composition and its biological activity

Abstract

Abstract Essential oil samples of Mentha x piperita L. (peppermint) were analysed by GC–MS and assayed for their antibacterial, antifungal and antioxidant activities. The steam‐distilled oil samples were obtained from autumn and spring planted crops which were treated with nitrogen and phosphorus fertilizers at different rates. The oil samples from spring planted crops had a significantly higher menthol and lower terpinen‐4‐ol concentrations than those from autumn planted crops. Mineral fertilization seemed to increase the content of menthol in the oil, and decreased that of menthone and β‐caryophyllene. The oil samples showed a different degree of inhibition against the twenty‐five microorganisms tested. Some differences were found between the oil samples from autumn and spring planted crops, the former being more active against some microorganisms, and the oil samples from fertilized peppermint seemed to be, on the whole, slightly more effective. Peppermint oil exhibited a marked antifungal activity against Aspergillus niger .