Isolation, Identification, Molecular and Electronic Structure, Vibrational Spectroscopic Investigation, and Anti-HIV-1 Activity of Karanjin Using Density Functional Theory

“Karanjin” (3-methoxy furano-2,3,7,8-flavone) is an anti-HIV drug, and it is particularly effective in the treatment of gastric problems. The method of isolation of “Karanjin” followed the Principles of Green Chemistry (eco-friendly and effortless method). The optimized geometry of the “Karanjin” molecule has been determined by the method of density functional theory (DFT). Using this optimized structure, we have calculated the infrared wavenumbers and compared them with the experimental data. The calculated wavenumbers are in an excellent agreement with the experimental values. On the basis of fully optimized ground-state structure, TDDFT//B3LYP/LANL2DZ calculations have been used to determine the low-lying excited states of Karanjin. Based on these results, we have discussed the correlation between the vibrational modes and the crystalline structure of “Karanjin.” A complete assignment is provided for the observed FTIR spectra. This is the first report of the isolation, molecular and electronic structure using vibrational spectroscopic investigation, density functional theory, and anti-HIV-1 activity of “Karanjin.