Abstract
In this study, Carum carvi L. essential oil (CEO) and Origanum majorana L. essential oil (MEO) was steam-distillated under reduced pressure. We henceforth obtained three fractions for each essential oil: CF1, CF2, CF3, MF1, MF2, and MF3. Then, these fractions were characterized using the gas chromatography–mass spectrometry (GC-MS) technique. The results indicated that some fractions were rich in oxygenated compounds (i.e., CF2, CF3, MF2, and MF3) with concentrations ranging from 79.21% to 98.56%. Therefore, the influence of the chemical composition of the essential oils on their antifungal activity was studied. For this purpose, three food spoilage fungi were isolated, identified, and inoculated in vitro, in order to measure the antifungal activity of CEO, MEO, and their fractions. The results showed that stronger fungi growth inhibitions (FGI) (above 95%) were found in fractions with higher percentages of oxygenated compounds, especially with (−)-carvone and terpin-4-ol as the major components. Firstly, this work reveals that the free-terpenes hydrocarbons fractions obtained from MEO present higher antifungal activity than the raw essential oil against two families of fungi. Then, it suggests that the isolation of (−)-carvone (97.15 ± 5.97%) from CEO via vacuum distillation can be employed successfully to improve antifungal activity by killing fungi (FGI = 100%). This study highlights that separation under reduced pressure is a simple green method to obtain fractions or to isolate compounds with higher biological activity useful for pharmaceutical products or natural additives in formulations.
Highlights
Over the last decade, several studies have shown the potential of using essential oils (EOs) as complementary medicine, i.e., for fungal diseases treatments
In view of these considerations, the deterpenation process is an effective choice to increase the yields of oxygenated terpenes and to remove hydrocarbons, which enhances the quality of EOs with regards to its biological activity
The chemical results of MEO and its fractions were a part of our previous published work [10], which demonstrates that reduced pressure steam distillation was an effective method used to obtain deterpenated fractions from Origanum majorana L. essential oil
Summary
Several studies have shown the potential of using essential oils (EOs) as complementary medicine, i.e., for fungal diseases treatments. Hydrocarbons compounds seem to have a limited contribution to the antifungal activity, as is mentioned in the literature [10,11] In view of these considerations, the deterpenation process is an effective choice to increase the yields of oxygenated terpenes and to remove hydrocarbons (terpeneless EOs), which enhances the quality of EOs with regards to its biological activity. This could promote their commercial value and even step up the possibility of upscaling the process [12]
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