COMPOSITION, ANTIFUNGAL ACTIVITY AND MAIN FUNGITOXIC COMPONENTS OF THE ESSENTIAL OIL OF MENTHA PIPERITA L.

Abstract

ABSTRACTTwenty‐one components (93.9% of the total chromatographic peak area) were tentatively identified in the essential oil (EO) of Mentha piperita L., based on Kováts retention indices (RIs), a mass spectral database (gas chromatography‐mass spectrometry, GC‐MS) and visual comparison of the mass spectra of the sample peaks with those of the database. The presence of 15 compounds (corresponding to 90.7% of the total chromatographic peak area) was confirmed by authentic standards. The EO presented a good activity against the following important postharvest deteriorating fungi: Aspergillus flavus, Aspergillus glaucus, Aspergillus niger, Aspergillus ochraceous, Colletotrichum gloesporioides, Colletotrichum musae, Fusarium oxysporum and Fusarium semitectum. At a concentration of 0.2% of the EO, all the fungi were completely inhibited, except for A. glaucus and C. musae which were inhibited 90 and 98%, respectively. TLC‐bioautography yielded three subfractions that prevented fungal growth, suggesting the presence of antifungals. Bioassay data of the crude EO were compared with those of the three subfractions. Based on these tests, it was concluded that several fungitoxics were responsible for the antifungal activity of M. piperita, with the principal ones being menthone, neomenthol, menthol and carvone. However, participation of other compounds cannot be ruled out. This is the first study in the literature that presents data on the activity of the crude EO against eight important postharvest deteriorating fungi, characterizing the amounts and types of comounds. In addition, also for the first time, the active fractions of the crude EO were isolated, identified and the components quantified. More detailed fungal tests are being conducted to confirm the tentative preliminary antifungal data.PRACTICAL APPLICATIONSDeterioration of agricultural products provoked by fungi accounts for considerable loss of crops of economic importance. Presently, these fungi are controlled by toxic synthetic chemicals. The food industry has significantly reduced the use of chemical preservatives. EOs have been known for their biological activities for many decades and they should, in principle, not be toxic to man and could replace toxic synthetic fungicides. This study demonstrates the potential of M. piperita EO as antifungal against C. gloeosporoides, C. musae, F. oxysporum, F. semitectum, A. niger, A. flavus and A. glaucus. Further studies are underway to evaluate M. piperita EO as a feed preservative. In addition, its principal active compounds were isolated and characterized. Identification of such components also helps to understand the mode of action of the extract, which can lead to the discovery of new antifungal compounds.