Synergistic Antifungal Properties, Chemical Composition, and Frontier Molecular Orbital Analysis of Essential Oils from Lemongrass, Kaffir Lime, Lime, Dill, and Shatavari Against Malassezia furfur

This study explores the chemical composition and synergistic anti-fungal properties of essential oils from the aerial parts of Satavari (<i>Asparagus racemosus</i> Willd.), Dill (<i>Anethum graveolens</i> L.), and lemongrass (<i>Cymbopogon citratus</i> Stapf), along with the peels of Lime (<i>Citrus aurantifolia</i> (Christm.)) and Kaffir lime (<i>Citrus hystrix</i> DC), as well as the leaves of <i>Citrus hystrix</i> DC, against <i>Malassezia furfur</i>, a yeast linked to dandruff and seborrheic dermatitis. Gas chromatography-mass spectrometry (GC-MS) identified key volatile compounds within these oils. In vitro anti-fungal assays evaluated their efficacy individually and in combinations using checkerboard dilution techniques to assess synergy. Results indicated significant antifungal activity, with lemongrass exhibiting the strongest effect (MIC of 0.125% <i>v</i>/<i>v</i>). Notably, a 1:1 combination of lemongrass and kaffir lime essential oils showed synergism, reducing the MIC to 0.0625% <i>v</i>/<i>v</i>. The antifungal activity was primarily attributed to citral and citronellal, with MICs of 0.03125% <i>v</i>/<i>v</i> and 0.125% <i>v</i>/<i>v</i>, respectively. Molecular orbital analysis revealed that the higher energy levels of the lowest unoccupied molecular orbitals (LUMOs) in citral correlate with greater antifungal efficacy, likely due to its enhanced electrophilicity, facilitating nucleophilic interactions with <i>M. furfur</i>'s cellular components. These findings highlight potential applications of essential oil combinations in antifungal therapies.