The benefits from the everyday use of essential oils are associated with well-known antimicrobial, anti-inflammatory, and antioxidant activity of their constituents. Considering this, compounds within essential oils are the focus of extensive research, necessitating the development of analytical methods for their simple and rapid determination. In this study, a method for the quantitation of p-cymene, limonene, eucalyptol, linalool, menthol, and carvone in essential oils was developed and validated.Gas chromatography-tandem mass spectrometry (GC-MS/MS) was employed for the separation and determination of the selected compounds. Standard solutions of six analytes were prepared using hexane as the solvent. A triple quadrupole mass spectrometer, operated in dMRM scan mode, was used to monitor specific transitions at their optimal collision energies (quantifier and two qualifiers for each compound). Gas chromatography was optimised by adjusting the oven temperature gradient programme to achieve efficient separation in a short run time of 14 min.All calibration curves showed good linearity (R2 ≥ 0.998), with the concentration ranges varying depending on the analyte (0.10–10.00 μg ml–1). The method was validated for accuracy (80.23–115.41 %), intra-day precision (≤ 12.03 %), and inter-day precision (≤ 11.34 %). The validation followed ICH guidelines, and all tested parameters were found to be satisfactory. This confirms the method’s suitability for the simultaneous individual determination of these compounds in essential oils. The method was successfully applied in the analysis of essential oils from lemon, tangerine, grapefruit, eucalyptus, myrtle, niaouli, peppermint, and fennel.

Foeniculum vulgare Mill. (fennel) is an edible and medicinal plant cultivated worldwide. Owing to its distinctive aroma and diverse biological activities, its essential oils (EOs) have been widely investigated. However, available data predominantly focus on cultivated fennel or commercial EOs, while comprehensive investigations of wild-growing Mediterranean populations—particularly comparisons among different plant parts—remain scarce. In this study, EOs obtained by hydrodistillation from stems, leaves, flowers, and fruits of native Croatian fennel, were chemically characterised using gas chromatography-mass spectrometry (GC-MS), while antimicrobial activity was evaluated using the disc diffusion method against four bacterial strains. Additionally, the volatile profiles of fennel hydrolates were determined by headspace solid-phase microextraction (HS-SPME) and GC-MS analysis. Fennel flowers gave the highest EO yield (1.95%), followed by mature fruits (1.43%), whereas significantly lower yields were obtained from leaves (0.69%) and stems (0.58%). Trans-anethole was identified as the dominant constituent (from 40.96% in stems to 80.71% in fruits), while α-phellandrene predominated in stem EO (42.77%). Hydrolate volatile profiles were more complex—particularly leaf hydrolate, where 29 compounds were identified. The principal constituents were trans-anethole (39.58–57.40%) and fenchone (16.01–28.80%), while the highest content of estragole was observed in fruit hydrolate (6.56%). The EOs demonstrated moderate antimicrobial activity, showing effectiveness exclusively against Escherichia coli, likely attributable to high phenylpropanoid (primarily trans-anethole) and fenchone contents.

Carbendazim, a widely used fungicide, is frequently detected in agricultural runoff and in surface and groundwater, raising environmental and public health concerns. The efficient removal of carbendazim from water sources remains a significant challenge, especially at different pH conditions. This study evaluates the sorption performance of several organic and inorganic materials for the removal of carbendazim (≈ 1 mg l−1) from aqueous solutions across a pH range of 3–6. A series of batch experiments was conducted using fruit-processing by-products (olive, cherry, and sour cherry pits) and various zeolite samples (natural zeolite clinoptilolite and its modified forms enriched with sodium, iron or sulphur). The results showed that only sodium-rich natural zeolite and sour cherry pits achieved notable removal efficiencies. Sodium-rich natural zeolite exhibited maximum performance of up to 99.0 % at pHo = 3.02, while sour cherry pits achieved 58.4 % efficiency at pHo = 5.81. The findings demonstrate that both sorbent type and solution pH are key factors affecting carbendazim removal. These findings provide a basis for the development of optimised, pH-sensitive sorption-based treatment strategies for pesticide-contaminated waters using environmentally friendly and readily available materials.

Nicotine is the main psychoactive component of tobacco and is considered to be the main substance responsible for the development of tobacco addiction. The main enzyme responsible for nicotine metabolism, CYP2A6, catalyzes the conversion of nicotine to cotinine and the subsequent metabolism of cotinine to trans-3′-hydroxycotinine. CYP2A6 activity is known to be modulated by various compounds, such as quercetin. This repeated-measures study examined the effects of short-term quercetin supplementation on urinary nicotine metabolism biomarkers in adult users of conventional and alternative nicotine products. Seventy-two participants completed a two-week study protocol involving first-morning urine collection at four time points: baseline, immediately after three days of quercetin supplementation (500 mg/day), seven days after supplementation, and ten days after supplementation. Urinary nicotine, cotinine, and trans-3′-hydroxycotinine concentrations were measured, and the nicotine metabolite ratio was calculated as trans-3′-hydroxycotinine/cotinine. Repeated-measures analysis of variance was used to evaluate biomarker changes over time according to sex, nicotine product type, and self-reported nicotine consumption intensity. Quercetin supplementation did not consistently alter nicotine metabolism biomarkers, while a descriptive increase in median urinary nicotine concentration after supplementation was observed in participants reporting lower daily nicotine consumption compared with other groups. These findings suggest that further studies are warranted to better clarify the effects of quercetin on nicotine metabolism across different levels of nicotine exposure.