The antifungal activity of essential oil (EO) from the Brazilian epazote (Chenopodium ambrosioides L.) was evaluated by the poison food assay at concentrations of 0.3%, 0.1%, and 0.05% with eight postharvest deteriorating fungi (Aspergillus flavus, Aspergillus glaucus, Aspergillus niger, Aspergillus ochraceous, Colletotrichum gloesporioides, Colletotrichum musae, Fusarium oxysporum, and Fusarium semitectum). EO components were tentatively identified by Kováts retention indices (RIs) using gas chromatography and gas chromatography combined with mass spectrometry (GC-MS). Growth of all fungi was completely inhibited at 0.3% concentration, and by 90% to 100% at 0.1% concentration. The following 13 tentatively identified compounds (relative percent) accounted for 90.4% of the total volatile oil: alpha-terpinene (0.9), p-cymene (2.0), benzyl alcohol (0.3), p-cresol (0.3), p-mentha-1,3,8-triene (0.2), p-cimen-8-ol (0.6), alpha-terpineol (0.5), (Z)-ascaridole (61.4), piperitone (0.9), carvacrol (3.9), (E)-ascaridole (18.6), (E)-piperitol acetate (0.5), and (Z)-carvyl acetate (0.3). Autobiographic thin layer chromatography of the EO to separate the principal fungitoxic fraction yielded only one fraction that completely inhibited the growth of all test fungi at a concentration of 0.1%. This fraction was characterized by RIs and GC-MS presenting a composition (%) of p-cymene (25.4), (Z)-ascaridole (44.4), and (E)-ascaridole (30.2). The results suggest ascaridoles were the principal fungitoxic components of the EO.

Twenty-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.

Extração de Chenopodium ambrosioides L. brasileiro revelou um baixo rendimento (0,3%) do óleo essencial (OE), com uma boa atividade contra oito fungos importantes. Visando melhorar a extração de antifúngicos, o extrato hexano foi avaliado. A extração hexânica melhorou o rendimento (1,1%) dos antifúngicos com uma atividade comparável ao OE. As composições químicas dos extratos, bruto e purificado, foram determinadas tentativamente por meio de cromatografia de fase gasosa (índices de retenção de Kováts) e cromatografia de fase gasosa-espectrometria de massas.Hydroextraction of the Brazilian Chenopodium ambrosioides L. produced a very low yield (0.3%) of the essential oil (EO) with a good activity against eight important fungi. Aiming to improve the yield of the antifungals, hexane was evaluated as an extraction solvent. Hexane extraction improved the yield (1.1%) of the antifungals with activity comparable to that of the EO. The chemical compositions of the crude and purified extracts were tentatively determined by gas chromatography (Kováts retention indices) and gas chromatography-mass spectrometry.Keywords: Brazilian Chenopodium ambrosioides L., hexane extract, antifungal activity, chemical composition IntroductionSpecies of Aspergillus, Colletotrichum, and Fusarium are the major causes of post-harvest economic losses of fruit, vegetables and grains in tropical ecosystems. These fungi are presently managed mainly by synthetic fungicides, posing health and environmental hazards. Thus, alternative safer compounds are needed to control these fungi. Although extracts of several edible botanicals are reported to have antifungal activity, 1-7 little work has been done to manage fungal deterioration of stored products by edible plant derived bioactive compounds. [8][9][10] Epazote (Chenopodium ambrosioides L.) is an herb native to South America, cultivated in sub-tropical and sub-temperate regions, mostly for consumption as leafy vegetable and herb. Because of its pungent flavor, it is traditionally used to season beans and other South American dishes. Its extract and essential oil (EO) are known to have medicinal, 11-14 acaricidal 15,16 and insecticidal [17][18][19] properties but there are only few reports on its antifungal properties. [20][21][22][23] Although a low fungal activity of dichloromethane extracts of epazote was reported, 22,23 neither its chemical composition nor the principal fungitoxic component were reported.In our previous study, we obtained satisfactory antifungal activity with the Brazilian C. ambrosioides EO. 21 However, it's very low yield (0.3% based on fresh weight basis) led us to investigate another extraction solvent. Since the EO contained non polar compounds 21 we have evaluated hexane in this study as it is non polar, inexpensive and widely available. In addition, we determined the fungal activity of the hexane extracts (crude and purified) against eight major postharvest deteriorating fungi, identifying its principal fungitoxic compound along with tentative chemical compositions b...

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