This study investigates the effects of extraction technique, solvent type, and geographical origin on the recovery of bioactive compounds from Arbutus unedo L. leaves collected from two Croatian islands (Vis and Mali Lošinj) and extracted using conventional, Soxhlet, and ultrasound-assisted extraction (UAE) with green solvents (distilled water, 70% ethanol, and ethyl acetate). Extracts were purified and characterized by thin-layer chromatography, column chromatography, and FTIR spectroscopy. Total phenols, hydroxycinnamic acids, flavonols, condensed tannins, and antioxidant capacity were quantified spectrophotometrically. Solvent type had the greatest influence, with 70% ethanol yielding the highest levels of bioactives and antioxidant capacity. Geographical origin significantly affected total phenolics and condensed tannins, with leaves from Vis outperforming those from Mali Lošinj. UAE was slightly more efficient than conventional and Soxhlet methods, particularly for thermolabile phenolics. Machine learning algorithms were applied as exploratory tools, using total phenols as a proxy variable to estimate selected bioactive compounds and antioxidant capacity based on extraction parameters. Decision Tree and Gradient Boosting models showed high goodness of fit within the experimental dataset (R² > 0.91). These results support the potential of green extraction strategies combined with data-driven screening for the valorization of A. unedo leaf extracts, while highlighting the need for further validation prior to industrial application.

The N-ferrocenoylation of uracil was studied to evaluate regioselectivity and optimise preparation protocols. Regioselectivity was monitored under various reaction conditions, with particular attention paid to the effects of the solvent and the base. Reactions in DMF were regiospecific, yielding only the N1 product, while reactions in CH₃CN produced both N1 and N1/N3 products, with ratios depending on the reaction conditions. The highest yield of N1/N3-diferrocenoyl uracil was achieved with an extended reaction time of 90 min using uracil and triethylamine. Optimised conditions were applied to C5-uracil derivatives, producing N1 and N1/N3 products. Regioselectivity and N-substitution were confirmed by NMR, and solvent effects were supported by quantum chemical calculations. The resulting ferrocene–pyrimidine conjugates exhibited oxidative and immunomodulatory activity, highlighting their biological potential.