Isolation and identification of Endophytic fungi associated with Adenanthera pavonina (Madatiya) leaves and evaluation of their antimicrobial potential.

Abstract

Scientists are exploring the potential of fungal endophytes to create new medications, recognizing their high bioactive content and potential for treating various diseases. The current study aimed to identify and isolate endophytic fungi from Adenanthera pavonina, a plant that belongs to the family Fabaceae and to evaluate their antibacterial activity. A. pavonina leaf segments were pretreated by cleaning and air-drying, then stored at 4 °C. Healthy, younger leaves were selected and cut under aseptic conditions. The segments were then sterilized in 70% ethanol, rinsed with distilled water, and dried with a sterile cotton cloth and incubated on Potato Dextrose Agar plates, followed by subculturing to isolate pure fungal strains. Two distinct fungal species were identified using cotton blue staining and microscopic screening from plant tissues. They had two different hyphal types: one with a cotton texture and quick growth, and the other with a cloudy texture with slow fungal growth. The two fungal isolates were cultured separately on Sabouraud Dextrose Broth. The fungal biomass was separated, and metabolites were extracted into an ethyl acetate phase. Crude extracts of each fungal strain were collected, dried, and dissolved in ethyl acetate for disk diffusion assay. Four bacterial strains were used for antimicrobial assays: Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Enterococcus faecalis by preparing streak plates using stock cultures. The turbidity of these suspensions was adjusted to the McFarland 0.5 solution. Once the correct turbidity was obtained, 100 μL of each microbial suspension was placed on Mueller Hinton Agar and prepared spread plates. The assay utilized a fungal extract as the test solution, with tetracycline antibiotic (0.02 g/mL) serving as the positive control and ethyl acetate as the negative control. Aseptically prepared antimicrobial disks were obtained, and each disk was loaded with 25 μL of the positive controller, negative controller, and test solutions. The experiment showed a clear zone of inhibition with tetracycline as the positive control, while ethyl acetate showed no antimicrobial effect in any plate. In contrast, the inhibition zone was not evident in the test samples. The fungal extract was found to be ineffective in inhibiting the bacterial strains.