# Prioritization of Drugs for Fungal Keratitis Eye Infections: An In-Silico Analysis
## 2 Result and Discussion
### Density Functional Theory Analysis  
In general, DFT studies are quantum mechanical approaches that describe the accurate structural and electronic properties of compounds. The electronic distribution information provides a clear picture of protein-ligand interactions, and the inhibition potential of Itraconazole is computed by orbital energy calculations. The computed highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energies reveal the high and low electron density regions of the optimized Itraconazole geometries, as shown in Figure 7. The red and green color distributions represent the positive and negative phases in the molecular orbital wave function, respectively. The protein-ligand interaction stability is calculated inversely with the energy gap between the interacting orbital [30].  
Figure 6: Inhibitory effects of the selected eight compounds on the rate of germination (%); (**a**) _Aspergillus flavus;_ (**b**) _Aspergillus fumigatus._The increasing HOMO energy (\(-3.7128\) eV) and decreasing LUMO energy (\(-3.8718\) eV) in the compound implies an enhancement in complex interaction stability and, hence, suggests strong binding with the receptor. It is observed that the Itraconazole exhibited the energy. The larger the HOMO-LUMO energy gap, the harder, more stable, and less reactive the molecule [31]. The smaller the HOMO-LUMO energy gap, the softer, less stable, and more reactive the molecule. The LUMO-HOMO energy gap (\(0.159\) eV) reflects the chemical activity of the molecule. The decrease in  
Figure 7: The highest occupied molecular orbital–lowest occupied molecular orbital (HOMO–LUMO) diagram of Itraconazole. **(a)** Optimized structure; **(b)** HOMO; **(c)** LUMO. The positive (red) and negative (green) phase distributions in the molecular orbital wave function. HOMO (electron donor regions) determines the ionization potentials. LUMO (electron acceptor regions) determines the electron affinity.  
the HOMO and LUMO energy gap explains the eventual charge transfer interaction taking place within the molecule due to the strong electron-accepting ability of the electron acceptor group. The strong charge transfer interaction is responsible for the bioactivity of the molecule. Thus, the DFT calculations performed here further substantiate our findings in molecular docking.  
Thus, this study suggests that RNAP from _A. flavus_ and _A. fumigatus_ can be considered a prioritized drug target and that Itraconazole, Ketoconazole, and Voriconazole may play a pivotal role in the development of new, and urgently-needed, anti-fungal drugs against fungal keratitis infections. However, further in-vitro and in-vivo studies are required to ascertain the anti-fungal activity and potential toxic effects of Itraconazole as a specific and direct inhibitor of RNAP from _A. flavus_ and _A. fumigatus_.  
In conclusion, the 3D structures of the RNAP sequences of hyalobyphomycetes, such as _A. flavus_ and _A. fumigatus_, that cause fungal keratitis were modelled through homology modelling. The binding efficacies of eight anti-fungal agents were tested for their prioritization against the modelled RNAP structures through molecular docking, and it was found that Itraconazole and Ketoconazole were effective against _A. flavus_, whereas Itraconazole and Voriconazole were active against _A. fumigatus_. Further, the chemical activity of Itraconazole was explored by computing the HOMO-LUMO energy gaps through DFT studies. The usage of Itraconazole might significantly show enhanced inhibition activity against RNA polymerase in fungus. Thus, Itracanazole could be used to treat the fungal diseases, including fungal keratisis, by targeting RNAP as an alternative drug target and overcoming drug resistance.