Owing to their potential applications, as well as their structural diversity, the discovery of novel secondary metabolites from insect-associated fungi has been of interest to researchers in recent years. The aim of this study was therefore to estimate the diversity of fungi associated with fungus-growing termites and bioprospecting these for potential secondary metabolites. In total, 18 fungal species were isolated and described from the gut and comb of Macrotermes barneyi based on 18S ribosomal DNA gene sequence analysis. Antimicrobial activity assays were carried out on all the known fungi, and nine isolates were recorded as active against pathogenic fungi. Xylaria escharoidea, the best performing isolate, was grown at laboratory scale and 4,8-dihydroxy-3,4-dihydronaphthalen-1(2H) was isolated and characterized. The minimum inhibitory concentration of this isolated compound against tested pathogenic organisms was found to be 6.25 μg. In addition, molecular docking studies have revealed that 4,8-dihydroxy-3,4-dihydronaphthalen-1(2H) is a prominent antibacterial agent with a marked interaction with key residues on protein A (agrA C) that regulates the accessory gene. The findings of this study support the drug discovery of antimicrobial properties in insect-associated fungi, which may lead to novel secondary metabolites.
Chemicals were procured from Sigma Aldrich and used as such without further purification. All solvents used for the spectroscopic and other physical studies were reagent grade and were further purified. Melting points were determined using a calibrated thermometer by Guna Digital Melting Point apparatus. They were expressed in degrees centigrade (°C) and are uncorrected. IR spectra were recorded as neat samples on Bruker Alpha-EcoATR-FTIR (Attenuated Total Reflection-Fourier Transform Infrared) interferometer with single reflection sampling module equipped with ZnSe crystal and reported in reciprocal centimetres (cm -1 ). 1 H and 13 C NMR spectra were recorded as solutions in DMSO-d 6 on a Bruker AMX 500 MHz spectrometer operating at 400 MHz for 1 H, 100 MHz for 13 C NMR. The 1 H and 13 C chemical shifts were expressed in δ with reference to
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