The aim of this work was to compare the antiradical activity, total phenol content (TPC), and essential oil composition of Origanum vulgare spp. virens, Origanum x applii, Origanum x majoricum, and O. vulgare spp. vulgare cultivated in Argentina in different localities. The experiment was conducted in the research station of La Consulta (INTA-Mendoza), the research station of Santa Lucia (INTA-San Juan), and Agronomy Faculty of National University of La Pampa, from 2007 to 2008. The composition of the essential oils of oregano populations was independent of cultivation conditions. In total, 39 compounds were identified in essential oils of oregano from Argentina by means of GC-MS. Thymol and trans-sabinene hydrate were the most prominent compounds, followed by gamma-terpinene, terpinen-4-ol, and alpha-terpinene. O. vulgare vulgare is the only Origanum studied which is rich in gamma-terpinene. Among tested oregano, O. x majoricum showed the highest essential oil content, 3.9 mg g(-1) dry matter. The plant extract of O. x majoricum had greater total phenol content values, 19.36 mg/g dry weight, than the rest of oregano studied. To find relationships among TPC, free radical scavenging activity (FRSA), and climate variables, canonical correlations were calculated. The results obtained allow us to conclude that 70% of the TPC and FRSA variability can be explained by the climate variables (R(2) = 0.70; p = 8.3 x 10(-6)), the temperature being the most important climatic variable.

Monoterpenes have antifungal activity on pathogenic fungi. The purpose of this study was to examine the effect of seven monoterpenes on phospholipid and sterol composition of Sclerotium cepivorum Berk as well as lipid peroxidation of mycelia and sclerotia development. Most of the monoterpenes increased the ergosterol content with a consequent diminution in the phospholipid/sterol ratio. This ratio was significantly decreased by the thymol treatment. When the fungus was grown in the presence of thymol or borneol, the saturated fatty acid content and the lipid peroxides were increased, concomitant with an increase of the sclerotial diameter. These results indicate that thymol and borneol may be promoting generation of lipid peroxides. Sclerotial differentiation was retarded mainly by camphor, 1,8-cineole, linalool and menthol. BioassayMinimal inhibitory concentrations (MIC) of the selected monoterpenes were determined by a screening test with the agar dilution method using PDA as the growth medium for fungi test (Dhingra and Sinclair, 1985).www.blackwell-synergy.com

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The effect of different dosages of thymol alone, iprodione alone and combinations of thymol and iprodione on white rot disease of garlic and its impact on soil microbial community structure were investigated under greenhouse conditions. Thymol alone or in combination with the fungicide iprodione did not appear to reduce either white rot incidence or soil sclerotia density as compared to an infected control. However, iprodione alone or in combination with thymol reduced soil fungal biomass. In addition, iprodione alone decreased soil microbial activity as estimated by fluorescein diacetate (FDA). Soil bacterial community structure as estimated by phospholipid fatty acid (PLFA) profiles was also was affected by both thymol and iprodione applications. The correlation biplot of the individual PLFAs and biocide treatment indicated that the treatments with thymol alone increased cyclopropyl fatty acid (cy17:0 and cy19:0), while the treatments with iprodione alone increased some saturated and branched fatty acids (principally i16:0, a15:0 and 18:0). In addition, taking into account PLFA biomarkers, thymol applications reduced Gram-negative bacteria in soil. To our knowledge, this research is the first report about the effect of a monoterpene (thymol) on soil microflora.

Biotechnological conversion of low-cost agro-industrial by-products, such as industrial waste or terpenes from the distillation of essential oils from plants into more valuable oxygenated derivatives, can be achieved by using microbial cells or enzymes. In Argentina, the essential oil industry produces several tons of waste each year that could be used as raw materials in the production of industrially relevant and value-added compounds. In this study, 1,8-cineole, one of the components remaining in the spent leaves of the Eucalyptus cinerea waste, was transformed by solid-state fermentation (SSF) using the two edible mushrooms Pleurotus ostreatus and Favolus tenuiculus. As a result, two new oxygenated derivatives of 1,8-cineole were identified: 1,3,3-trimethyl-2-oxabicyclo [2.2.2]octan-6-ol and 1,3,3-trimethyl-2-oxabicyclo [2.2.2]octan-6-one. Additionally, changes in the relative percentages of other aroma compounds present in the substrate were observed during SSF. Both fungal strains have the ability to produce aroma compounds with potential applications in the food and pharmaceutical industries.

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