Synergistic Essential Oil Blends: Chemical Composition, Antimicrobial Activity and Antioxidant Properties for Cosmetic Preservation

ABSTRACT This study explores the chemical composition, antimicrobial synergy and antioxidant properties of essential oil blends from Thymus vulgaris , Origanum vulgare , Rosmarinus officinalis , Lavandula angustifolia and Cinnamomum verum as natural preservatives in anti‐ageing cosmetic emulsions. Gas chromatography–mass spectrometry (GC–MS) identified key bioactives (thymol 45.23%, carvacrol 72.56%, trans‐cinnamaldehyde 74.32%), driving broad‐spectrum activity against Staphylococcus aureus , Pseudomonas aeruginosa , Escherichia coli , Candida albicans and Aspergillus brasiliensis . Synergistic blends (e.g., thyme‐oregano, FICI ≤ 0.375) reduced minimum inhibitory concentrations by 50%, meeting ISO 11930:2019 standards (> 3 log reduction for bacteria, > 1 for fungi by Day 14). Antioxidant properties maintained peroxide values at 3.67 meq O 2 /kg and TBARS at 0.56 mg MDA/kg over 6 months at 40°C, extending shelf‐life by 2–3 months. Statistical validation (ANOVA, Tukey's test, p < 0.01) confirmed efficacy and stability. Sensory scores (> 7.5/9) highlight consumer appeal. These analytical insights underscore the potential of essential oil blends as sustainable alternatives to synthetic preservatives, with implications for analytical chemistry in cosmetic material development.