Variability of chemical composition and biological activities of Allium triquetrum L. essential oils

The present work describes the chemical composition and evaluates the antimicrobial properties of the essential oils from the Tunisian Allium triquetrum L. It is particularly interesting study because there are no reports on of this species in any sector and with specific chemical composition. The chemical composition of four essential oil samples (flowers, stems, leaves and bulbs) of A. triquetrum, obtained separately by hydrodistillation were analyzed by combination of GC-FID and GCMS. Altogether, 45 compounds were identified representing 90.5-95.3% of the total oil content. The chemical composition of bulbs oil was characterized by a high proportion of sulfurous compounds (81.9%) among which dipropyl trisulfide (11.7%) and di-2-propenyl trisulfide (10.0%) were the predominant compounds. The oxygenated sesquiterpenes represent the major fraction (79.2%) in stem oil giving T-cadinol (26.8%), α-eudesmol (11.4%) and β-eudesmol (16.8%) as the main components; they were present also in leaf oil. We also noted the presence of some alkane compounds such n-nonadecane (13.3%) in flower oil. Some compounds identified in this plant have not been reported about other species of Allium such elemol, β-copaen-4-α-ol, globulol, viridiflorol, guaiol, eremoligenol, α-eudesmol, β-eudesmol and pimaradiene. Furthermore, the isolated oils were evaluated for antibacterial and antifungal activities. All the oils exhibited significant in vitro antibacterial activity, especially against Enterococcus faecalis and Staphylococcus aureus. The oil obtained from the stem, leaf and bulbs exhibited an interesting antibacterial activity, with a Minimum Inhibitory Concentration (MIC) of 31.25µg/mL against S. aureus. It was found also that stem and bulbs oil showed the highest growth inhibition of almost fungi especially against Fusarium solani (75.33and 71.33%, resp.) even greater than the positive control: benomyl (69.33%). The results indicate that the essential oil of A. triquetrum contains chemical compounds with good potential for application in natural health products and in the protection of agriculture products