GC-MS Profiling, Antioxidant and Enzyme Inhibitory Activities of Basil (Ocimum basilicum L.) and Clove (Syzygium aromaticum L.) Essential Oils and Their Binary Mixtures

Combining essential oils (EOs) with contrasting chemical profiles may result in biological effects that cannot be reliably predicted from the properties of the individual oils. This study evaluated the chemical composition, biological activities, and interactions of basil (Ocimum basilicum L.; EOB) and clove (Syzygium aromaticum L.; EOC) essential oils. Gas chromatography–mass spectrometry (GC-MS) identified 41 volatile constituents in EOB and 29 in EOC. EOB was dominated by estragole (73.0%) and methyl eugenol (7.2%), whereas EOC was characterized mainly by eugenol (55.0%) and (E)-β-caryophyllene (32.9%). The oils were tested individually over a concentration range of 2.5–500 µg/mL, while binary EOB:EOC mixtures (1:1, 1:2, and 2:1; v/v) were evaluated at total essential oil concentrations of 5, 25, and 50 µg/mL. Antioxidant activity was assessed using linoleic acid peroxidation and ABTS•+ radical scavenging assays, whereas enzyme-inhibitory activity was evaluated against cyclooxygenase-2 (COX-2) and collagenase. EOC showed stronger ABTS•+ radical scavenging activity and greater inhibition of COX-2 and collagenase, while EOB exhibited greater inhibition of lipid peroxidation. Bliss independence analysis revealed concentration- and ratio-dependent interactions. Synergy (ΔBliss > +10 percentage points) was observed for the 1:2 EOB:EOC mixture at 5 and 25 µg/mL in the COX-2, collagenase, and ABTS•+ assays, and for all three mixture ratios at 5 µg/mL in the lipid peroxidation assay; no antagonistic interactions were detected. These findings demonstrate that the biological activity and interaction profiles of basil–clove essential oil mixtures depend on both mixture composition and concentration. Further studies in cell-based and in vivo models are required to confirm their efficacy, mechanisms of action, and safety.