Unveiling the Multifaceted Capabilities of Endophytic Aspergillus flavus Isolated from Annona squaMosa Fruit Peels against Staphylococcus Isolates and HCoV 229E—In Vitro and InSilico Investigations

Abstract

In an effort to find new ways to treat infections that are resistant to many drugs, there has
been a recent uptick in the pursuit of more archaic therapy methods. Endophytes are a treasure trove
of medicinally important secondary metabolites that have so far been undiscovered. In this study, the
endophytic fungi found in Annona squamosa L. fruit peels will be identified and isolated using
morphological, microscopical, and ITS-rDNA sequence analysis. The secondary metabolites of the
fungus will be extracted using ethyl acetate, and the chemical profile will be investigated using
UPLC/MS. Finally, the study will assess the possibility of antibacterial, antibiofilm, and antiviral
activities. The fruit peels were used to isolate an endophytic fungus, which was later determined to be
Aspergillus flavus L. Seven chemicals belonging to different chemical classes were identified by the
UPLC/MS. The agar diffusion technique was used to test the antibacterial activity of the fungal ethyl
acetate extract (FEA) against several Gram-positive and Gram-negative standard strains, as well as
resistant clinical isolates. The crude fungal extract was tested for its potential antiviral efficacy against
low pathogenic human coronavirus (HCoV 229E) using the CPE-inhibition assay. Both methicillin-
sensitive and methicillin-resistant Staphylococcus aureus (MRSA and MSSA) were effectively
inhibited, indicating the presence of selective Gram-positive antibacterial and antibiofilm properties.
But it was noticeably ineffective against Gram-negative bacteria when tested with the extract. With an
IC50 value of 27.2 μg/mL against HCoV 229E, the ethyl acetate extract of Aspergillus flavus L
demonstrated intriguing antiviral activity. In addition, the discovered metabolite showed a promising
affinity for three MRSA biotargets and the major protease of HCoV 229E, as compared to previously
published reference inhibitors/substrates, according to in silico virtual molecular docking-coupled
dynamics simulation. The possible oral bioavailability of the identified metabolites was lastly
evaluated by ADME analysis.