Multi-scale study on the volatility of essential oil and its modulation methods

Abstract

Essential oil (EO), a mixture of volatile components with diverse pharmacological effects, faces challenges due to volatility impacting therapeutic efficacy. To address this, we developed an integrated multiscale methodology combining simultaneous thermal analysis, gas chromatography, and molecular dynamics simulations. This approach quantitatively explores EO component volatility and elucidates the mechanisms by which fixatives (nerolidol, farnesol, ethyl cinnamate) and 13X-HP zeolite encapsulation modulate volatilization. Our findings demonstrate that volatility is primarily governed by molecular structural class, molecular weight, and functional groups. Based on volatility parameters (e.g., T_max ranging from 124.1 °C to 260.0 °C, volatilization in 12 h ranging from 33.12 % to 100 %, etc.), EO components were categorized into top (>95 % volatilization in 2 h), middle, and base (<50 % volatilization after 12 h) notes, providing a choice basis for duration-specific aromatherapy. Notably, low-volatility EOs showed potential as fixatives. Mechanistic insights revealed that the ethyl cinnamate prolongs the volatilization of representative EO components by 10.76 %–24.02 % through polarity-modulated intermolecular interactions modulated by polarity, irrespective of its own volatility. For zeolite encapsulation, 13X-HP exhibited pore-size (∼10 Å) dependent effects: effectively delaying the release of smaller monoterpenes (e.g., ocimene volatilization decreased 3.95 %) but unexpectedly accelerating the release of larger components (e.g., citral volatilization increased 12.59 %). The modulated release was governed by adsorption location, component characteristics, and adsorption energy (<−31470.4 kJ/mol correlating with longer release). Critically, the strong concordance between macroscopic experiment data and microscopic simulations validates this integrated methodology as a powerful tool for the rational selection of EO components and the design of controlled-release systems.