Diisooctyl Phthalate, A Major Bioactive Metabolite With Antimicrobial Activity Isolated From Endophytic Fungus Hypoxylon griseobrunneum Symbiotic With The Medicinal Plant Thunbergia Fragrans Roxb.

This study investigates the isolation and bioactivity of endophytic fungi from Thunbergia fragrans, collected from Mysore, Karnataka,India. After surface sterilization, six distinct fungal isolates (TF2, TF3, TF7, TF11, TF12, and TF20) were cultured on Potato Dextrose Agar (PDA) and evaluated for their antimicrobial properties. The crude extracts of all six fungal isolates showed antibacterial activity, with TF3 demonstrating the most significant inhibition against both Gram-positive and Gram-negative bacteria, including Bacillus subtilis, Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa. The TF3 extract exhibited the largest inhibition zones, particularly against B. subtilis (23±0.18 mm). Further analysis of TF3 revealed its Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) values to be 5±0.18 mg/ml to10±0.09 mg/ml, with IC50 values ranging from 1.09 ±  0.01mg/ml to 1.875±0.00 mg/ml, confirming its strong antibacterial potential. Additionally, the antifungal activity of TF3 was assessed, with the extract showing notable inhibition against Aspergillus fumigatus, Candida albicans, Fusarium oxysporum, and Penicillium chrysogenum. GC-MS analysis identified several bioactive compounds, including Diisooctyl phthalate, which is known for antimicrobial properties. Structural identification of the compound was confirmed through FT-IR and NMR spectroscopy. Phylogenetic analysis based on ITS sequences identified TF3 as Hypoxylon griseobrunneum. These results highlight the antimicrobial and bioactive potential of T. fragrans endophytes, particularly TF3, suggesting its potential as a valuable source of natural bioactive compounds for therapeutic applications. This study opens avenues for further exploration into the medicinal properties of endophytic fungi from T. fragrans.