Chemical Analyses, Antifungal and Insecticidal Properties of the Essential Oils of Eryngium Tricuspidatum L. (Apiaceae) Growing Natively in Tunisia

The present study investigated the interspecific variability of organic volatiles, the antifungal and insect repellency activities of the essential oils from two subspecies of Eryngium tricuspidatum; E. tricuspidatum subsp. tricuspidatum (E.t.S.t) and E. tricuspidatum subsp. bovei (E.t.S.b) (an Algerian-Tunisian endemic taxon) growing wild in Tunisia. The phytochemical characterization was carried out by using the hybrid analytical technique: gas chromatography paired with mass spectrometry (GC/MS), combined with gas chromatography-flame ionization detection (GC/FID). As a result, fifteen and nineteen compounds representing 80.3% and 90.2% of the total volatiles were identified in subspecies bovei and tricuspidatum oils, respectively. Importantly, both analytes were distinguished by a high proportion of sesquiterpene hydrocarbons 61.1% in (E.t.S.b) and 46.4% in (E.t.S.t). β-bisabolenal (17.8%), bicyclogermacrene (11.9%) and trans-muurola-3,5-diene (11.5%) were detected as the main odorants of tricuspidatum subspecies, whereas bovei essential oil was mainly composed of bicyclogermacrene (27.1%) and trans-muurola-3,5-diene (20.9%). The antifungal potential of the tested oils was evaluated towards three fungal species: Candida albicans, C. glabrata and Trichophyton rubrum. Both essential oils manifested promising anti-candidal activity against C. albicans as their Minimum Inhibitory Concentrations values (MIC₅₀) were less than 0.25 mg.mL^− 1. In addition, the volatile oil obtained from subspecies bovei demonstrated the most potent inhibitory activity against the dermatophytic fungus T. rubrum, with MIC₅₀ value of 0.5 mg.mL^− 1. The repellency and toxicity of these oils were assayed towards T. confusum, the primary insect pest of stored cereals. Notably, the repellent effects achieved (50 and 60)% for tricuspidatum and bovei, respectively.