Advanced Spectroscopic Characterization, Antioxidant and Antibacterial Activity Evaluation, and Trace Metal Analyses of Essential Oils from Star Anise, Nutmeg, Clove, Oregano, Bay Leaves, and Lemon Peel

Essential oils from star anise, nutmeg, clove buds, oregano, bay leaves, and lemon peel were extracted via hydrodistillation. GC-MS, UV–Vis, FTIR, and 1H NMR spectroscopy were used to identify the major compounds (trans-anethole, sabinene, eugenol, carvacrol, eucalyptol and limonene, for star anise, nutmeg, clove buds, oregano, bay leaves, and lemon peel essential oil, respectively), revealing that the spectra were dominated by the oils’ primary constituents. Antioxidant activity was assessed using DPPH and ABTS assays, demonstrating high radical scavenging ability, especially for bay leaf and oregano oils. Despite phenolic content being correlated with antioxidant activity, discrepancies were found, suggesting that non-phenolic compounds and synergism also play a role. Antibacterial evaluation showed significant activity for bay leaf and oregano oils, particularly against Klebsiella pneumoniae and Pseudomonas aeruginosa, due to phenolic and terpene compounds. The presence of trace metals in the oils, including those with antimicrobial and antioxidant properties such as Cu, and Zn, was also analyzed. The risk assessment showed that toxic metals were below harmful thresholds.