Gas chromatography combined with mass spectrometry and flame ionization detection for identifying the organic volatiles from Stachys arvensis, S. marrubiifolia and S. ocymastrum

Comparative analysis on the chemical composition and biological properties of the volatile fractions obtained from three Stachys species (S. arvensis, S. marrubiifolia and S. ocymastrum) growing in Tunisia is reported, for the first time, in the present work. The volatile organic compounds were extracted by hydrodistillation in a Clevenger-type apparatus, then analyzed using CG-FID and CG-MS. 37, 34 And 39 components were identified and quantified in previously mentioned species, respectively. It's noticeable that more than 30% of the volatiles constituting each species are hydrocarbons. Taking into account only the identified compounds, the terpenes content in three Stachys species is lower than 20%. In addition, the comparative study of the chemical composition of these taxa showed that S. ocymastrum volatile fraction was characterized by its richness in phenlypropanoide (E)-anethol (18.1%) and hexahydrofarnesyl acetone (8.9%) in comparison with the two-other species. Moreover, the volatile fractions of S. arvensis and S. marrubiifolia showed a similarity in their chemical compositions. The antimicrobial activities were investigated using the micro-well plate dilution assay for five bacterial strains (Escherichia coli, Salmonella enterica, Pseudomonas aeruginosa, Staphylococcus aureus and Bacillus subtilis), for Candida albicans (ATCC 30031) yeast and the agar incorporation method for Aspergillus niger and Penicillium Spp. filamentous fungi. The results have shown significant antimicrobial activities against all tested bacteria and Candida albicans human pathogenic yeast. The minimal inhibitory concentrations, MIC values ranged from 156 to 625 μg mL−1. However, the volatile fractions presented a very low antifungal effects against Aspergillus niger and Penicillium spp.