Structural, electronic, and thermodynamic characterization with spectroscopic, topological, reactivity, and molecular...

The bioactive organosulfur compound diallyl sulfide (DAS), found in garlic and onions, was analyzed using density functional theory (DFT). DAS exhibits antimicrobial and anticancer properties, making it a potential candidate for drug discovery. Geometry optimization revealed bond lengths and angles consistent with electron delocalization. Frontier molecular orbital analysis showed increased HOMO-LUMO gaps and stability in polar solvents. Natural bond orbital analysis confirmed significant charge delocalization via sulfur-centered interactions, explaining the partial S-C double-bond character and weakened adjacent CH bonds, thus supporting electrophilicity trends. Thermodynamic properties displayed temperature-dependent changes, while UV-Vis spectra showed reduced λ_max in polar solvents owing to excited-state destabilization. The density of states indicates the excess electron density near the conduction band. The reduced density gradient plots identified the stabilizing van der Waals interactions. Molecular electrostatic potential mapping of electrophilic (sulfur) and nucleophilic (allyl H) sites was validated by Fukui function analysis. Druglikeness evaluation indicated that DAS satisfies Lipinski's and Veber's rules for oral bioavailability, but requires structural refinement to enhance complexity. Molecular docking with proteins 3IAI, 3E4E, and 4EY7 revealed hydrophobic and π-sulfur interactions, confirming their biological relevance.