Seasonal Variation in the Chemical Profile, Antifungal and Insecticidal Activities of Essential Oils from Daucus reboudii

Purpose: This study investigates for the first time the influence of seasonal variation on the chemical composition, antifungal and insecticidal potentials of essential oils extracted from Daucus reboudii growing in Tunisia. Methods: Essential oils were extracted in summer (vegetative stage) and autumn (flowering-fruiting stage) by hydrodistillation, the corresponding volatiles were identified by gas chromatography coupled with mass spectrometry (GC/MS). The anti-insect potency of the essential oils from D. reboudii collected seasonally was evaluated towards two stored product insects, Tribolium confusum and Sitophilus zeamais. The antifungal effects of these oils were screened against Candida albicans and Candida glabrata yeasts and Trichophyton rubrum and Microsporum canis dermatophytes, fungi with medical interest. Results: The essential oil highest yield was recorded from the sample collected in October. The phytochemical profiling of D. reboudii volatile oils indicated that monoterpene hydrocarbons (52.2–61.4)% represent the major class of the identified compounds, with -pinene (36.6–40.6)% as the major secondary metabolite through both seasons. Taking into consideration the second most represented class of compounds, a predominance of sesquiterpenes hydrocarbons (25.3%) was observed in summer, versus a predominance of phenyl derivatives (21.1%) in the flowering-fruiting stage. The essential oils showed promising effect in protecting stored grains from T. confusum attacks. The essential oils from D. reboudii showed interesting antifungal potential towards T. rubrum and M. canis. C. Conclusion: These results may be gainful in choosing the optimal harvest time for the production of D. reboudii active agents, with high value in crops preservation and medication. Graphic Abstract: [Figure not available: see fulltext.