Antifungal Activity of Hedychium spicatum Essential Oil Against Candidemia-Causing Candida tropicalis and Candida parapsilosis: In Vitro Evaluation and Computational Identification of Cis-γ-Bisabolene as a Putative CYP51-Binding Constituent.

Candidiasis is caused by Candida parapsilosis and Candida tropicalis emerges due to antifungal resistance and limited therapies. We aim to assess the antifungal activity of Hedychium spicatum essential oil (HSEO), followed by computational analyses to identify potential lead phytochemicals, targeting lanosterol 14α-demethylase (CYP51), a key enzyme in ergosterol biosynthesis. GC-MS identified 29 phytoconstituents, with τ-cadinol (17.94%) as the major component. Disc diffusion demonstrated concentration-dependent antifungal activity against C. parapsilosis and C. tropicalis, with inhibition zones of 11.00 ± 0.53 and 10.40 ± 0.36 mm, respectively, at 100% (v/v). Homology models of CYP51 exhibited structural reliability based on Ramachandran and validation metrics. Molecular docking identified cis-γ-bisabolene with the lowest binding energies (-7.6 and -7.9 kcal/mol) against haem-free CYP51 models of C. parapsilosis and C. tropicalis, respectively, through hydrophobic interactions. ADMET predictions indicated favorable oral absorption, Lipinski compliance, minimal CYP450 inhibition risk, and no hepatotoxicity or mutagenicity. MD simulations confirmed stable complexes using RMSD, RMSF, Rg, and SASA profiles. MM-PBSA showed favorable binding energies of -6.02 and -8.05 kJ/mol compared to fluconazole (0.98 and 0.66 kJ/mol). DFT showed comparable HOMO-LUMO gaps (6.216 and 6.176 eV) and global hardness (3.108 and 3.088 eV). Overall, HSEO shows promising antifungal potential, with cis-γ-bisabolene as a lead candidate.