Spectroscopic and structural studies of fukugiside and morelloflavone biflavonoids in different Media combined with DFT and molecular docking calculations

The structural features and intramolecular interactions of morelloflavone (MFL) and its glycoside fukugiside (FKS) from Garcinia species were investigated using B3LYP/6–311++G(d,p) level of theory. ¹H NMR, ¹³C NMR, FT-IR, FT-Raman, and UV–Vis spectroscopic analyses were also performed. Electronic absorptions were explored with TD-DFT in the gas phase and solvents (chloroform, DMSO, acetone), revealing significant solvent effects on electronic transitions. UV–Vis spectra in chloroform corroborated theoretical predictions, with key transitions attributed to LP (2) O7 → π* (C27-C30) and LP (2) O9 → π* (C33-C35), stabilized at 30.89 kJ/mol and 29.44 kJ/mol, respectively, as identified through NBO analysis. Non-covalent interactions and electronic localization were characterized through topological tools such as ELF, LOL, and RDG, elucidating weak interaction regions and electron density distribution. The molecular electrostatic potential (MEP) map was used to identify the reactive sites of the molecules, while TDOS and transition density matrix (TDM) analyses confirmed efficient charge transfer within the molecules. Biological insights were obtained through in silico studies. MFL exhibited promising tuberculosis inhibition, while FKS showed potential antiviral activity against COVID-19. Molecular docking results were validated by 100 ns molecular dynamics simulations, confirming the stability of ligand-receptor complexes. Additionally, ADMET profiling affirmed the drug-likeness and pharmacokinetic viability of both molecules. This integrated study highlights the structural, electronic, and pharmacological attributes of MFL and FKS.