Profiling of essential oil chemical composition of some Lamiaceae species extracted using conventional and microwave-assisted hydrodistillation extraction methods via chemometrics tools

This study investigated the potential use of microwave energy as an effective technique for the extraction of essential oil (EO) from some plant species belonging to Lamiaceae family growing in Egypt, involving Origanum majorana L., Mentha pipereta L., Mentha longifolia L., Origanum syriacum L., Lavandula angustifolia L., Rosmarinus officinalis L., and Thymus vulgaris L., in comparison with conventional extraction using hydrodistillation (HD) approach, in terms of extraction time, oil yields, and chemical composition. The results showed that the use of microwave in a relevant technique, namely microwave-assisted hydrodistillation (MAHD) required an extraction of 60 minutes, while HD required 180 minutes. In general, EO yield being extracted by MAHD was higher than those extracted by HD. Gas chromatography in combination with mass spectrometry (GC/MS) analysis indicated noticeable quantitative changes in EOs composition extracted by MAHD and HD extraction methods. Except for O majorana L., GC/MS analysis of extracted oils using MAHD showed higher amounts of oxygenated constituents compared to HD extraction. The results of this study introduced MAHD as rapid, economical and environmental friendly extraction method. A comparative analysis was stated here between the EOs of all plant species under study on chemometric tools such as principal components analysis (PCA) and agglomerative hierarchical clustering (AHC). In general, the PCA results showed that there is significant variation between species in the quality and quantity of EO composition. However, no significant difference is observed based on the extraction method used (HD and MAHD).