Effect of Plant Material Treatment on the Phytochemical Profile in Extracts of Fennel (Foeniculum vulgare Mill)

Background: The phytochemical composition of fennel leaf preparations may vary with the condition of the plant material, the extraction solvent and the duration of contact during preparation. Aim: This study assessed the qualitative profiles of selected metabolites in extracts of Foeniculum vulgare Mill. leaves subjected to different treatments. Methods: Fennel leaves were examined fresh, after oven drying, after refrigerated storage for seven days, or after freezing for seven days. Aqueous infusions were prepared with contact times of 5 and 20 minutes. Fresh leaves were also macerated in ethyl acetate for 5, 10, 20, and 30 minutes. Extracts underwent dispersive liquid–liquid microextraction followed by gas chromatography–mass spectrometry to identify the metabolites detected under each condition. Results: Maceration of fresh leaves in ethyl acetate yielded detectable L-fenchone and anethole at all four contact times. Aqueous infusions produced profiles containing up to four compounds: D-limonene, L-fenchone, estragole, and anethole. All four were detected in infusions of fresh and frozen leaves at both contact times. Infusions of dried leaves contained D-limonene and anethole, whereas those of refrigerated leaves contained only anethole. Extending infusion contact from 5 to 20 minutes did not change the qualitative profile within any of the four plant-material conditions. Conclusion: Within the conditions tested, the initial treatment of fennel leaves was associated with greater differences in the detected phytochemical profiles than infusion contact time. These findings describe qualitative differences and do not establish changes in metabolite concentrations or biological effects.