In vitro and in silico antimicrobial, antioxidant, and cytotoxic potentials of endophytic Alternaria alternata MPL5 from Mentha piperita

Mentha piperita (Lamiaceae) is well known for its medicinal properties, yet the biotechnological potential of its endophytic fungi remains underexplored. This study isolated and characterized endophytic fungi from M. piperita leaves, assessing their in vitro and in silico antimicrobial, antioxidant, and cytotoxic activities. The endophytic fungus was isolated on potato dextrose agar and identified using morphological characteristics and 18sRNA sequencing. The fungus was identified as Alternaria alternata MPL5 and submitted to GenBank (ID: OR994590.1). The ethyl acetate extract of the fungus exhibited high cytotoxic activity (IC50 = 60.41 µg/ml) against Hep G2 cell lines. The extract demonstrated robust antioxidant properties in DPPH radical-scavenging assay (IC50 = 51.66 µg/ml), hydrogen peroxide assay (IC50 = 137.64 µg/ml), reducing power assay (0.125 OD at 100 µg/ml), and total antioxidant assay (0.169 OD at 100 µg/ml). Additionally, the extract displayed moderate antimicrobial activity against Bacillus subtilis (21.00 ± 1.00 mm), Salmonella typhi (19.66 ± 1.15 mm), Staphylococcus aureus (17.33 ± 0.57 mm), and Escherichia coli (17.66 ± 1.52 mm). GC-MS analysis of the extract revealed the presence of bioactive compounds, notably 7,9-Di-tert-butyl-1-oxaspiro (4,5) deca-6,9-diene-2,8-dione, constituting 18.32% of the peak area. GC-MS-identified compounds were docked against six therapeutic targets. CID 5,360,741 showed strong binding with MurA, catalase, and HER2, forming stable hydrogen bonds, while CID 15,438,745 had the highest affinity with EGFR (− 9.0 kcal/mol). ADMET analysis identified CID 545,303 as the safest, with no AMES toxicity or hERG inhibition and 98.2% intestinal absorption. These findings highlight the pharmacological promise of the identified bioactive molecules as antioxidants, antimicrobials, and cytotoxic agents, revealing the untapped biotechnological potential of endophytic fungi in medicine and natural product discovery.