Extraction methods, chemical composition and biological activities of essential oils

Essential oils (EOs) represent a rich source of natural bioactive molecules with relevance to human health, food, agriculture, and other bio-based applications. Their composition and biological properties are shaped by botanical origin, edaphoclimatic conditions, developmental stage, and extraction conditions. This review examines current knowledge of EO extraction methods, chemical composition, and biological activities. Hydrodistillation and steam distillation remain widely used, while supercritical CO₂, microwave-, ultrasound-, and enzyme-assisted extraction provide alternative routes for improving recovery and selectivity. Terpenoids and phenylpropanoids dominate EO composition, alongside less abundant volatile constituents. Their chemical diversity and interactions underpin antimicrobial, antioxidant, anti-inflammatory, and other biological effects through multiple molecular and cellular mechanisms. Recent research further explores anti-virulence effects, synergistic interactions, and nano-enabled delivery. Wider application, however, is challenged by compositional variability, instability, volatility, poor aqueous solubility, safety concerns, and formulation constraints. Standardized extraction and chemical characterization, harmonized biological assays, and stronger in vivo and clinical evidence are needed to improve the reproducibility, safety, and practical use of EOs.