Morphological, Functional, and Molecular Characterization of the Selected Fungal Endophytes from Neolamarckia cadamba (Roxb.) Bosser

Background Higher plants serve as a valuable source of endophytic fungi, which have been shown to produce a wide range of secondary metabolites with therapeutic potential. Despite extensive studies on endophytes from various plant species, there have been no prior reports on the isolation and characterization of endophytic fungi from Neolamarckia cadamba (Roxb.) Bosser is a medicinally important tree native to tropical Asia. This study aimed to isolate and identify endophytic fungi from the leaves and stems of N. cadamba and assess their phytochemical constituents and biological activities, particularly antioxidant and antimicrobial potential. Results A total of eight endophytic fungi were isolated from N. cadamba , with seven from leaves (NKL1 to NKL7) and one from the stem (NKS1). NKL1, NKL3, and NKL4 exhibited rapid growth and distinct morphological features, and were therefore selected for further analysis. Phytochemical screening of fungal extracts revealed the presence of alkaloids, flavonoids, and carbohydrates. The antioxidant activity, assessed via the DPPH assay, showed a concentration-dependent increase in free radical scavenging ability, with NKL1 and NKL3 exhibiting the highest antioxidant potential, comparable to that of the standard ascorbic acid. The crude extracts of endophytic fungi NKL1, NKL3, and NKL4 exhibited concentration-dependent antibacterial activity against Staphylococcus aureus , Klebsiella pneumoniae , and Escherichia coli , with NKL1 and NKL3 demonstrating the highest inhibitory effects, thereby confirming their antimicrobial potential. Morphological characterization and 18S rRNA gene sequence analysis identified NKL1 and NKL3 as Curvularia lunata and Curvularia tropicalis (NCBI GenBank accession numbers PX205205 and PX218454, respectively), both of which belong to the phylum Ascomycota. Conclusion This study provides the first report of Curvularia lunata and Curvularia tropicalis as endophytic fungi associated with Neolamarckia cadamba . The isolates NKL1 and NKL3 exhibited strong antioxidant and antibacterial properties, suggesting their potential as promising sources of bioactive compounds. These findings support further exploration of N. cadamba -associated endophytes for their therapeutic and industrial applications.