Abstract

Endophytic microorganisms hold immense promise as sources of diverse and potentially bioactive compounds, making them a focal point of investigation in natural product research. In this study, natural products have been explored from symbiotic fungi and bacteria isolated from organisms collected from three distinct collection sites in Egypt. The Orman Garden in Giza, the soda lakes of Wadi Natrun, and the coral reefs of Hurghada, representing ecologically diverse habitats rich in microbial diversity. The strains collected and cultured have most likely never been screened against disease targets and so have high potential to harbour novel bioactive natural products that have yet to be studied. A total of 31 samples were collected from these sites, yielding 87 microbial isolates: 12 isolates from Orman Garden, 45 from Wadi Natrum, and 30 from Hurghada. The microbial extracts obtained have been biologically evaluated against microbial, biofilm and acetylcholinesterase targets, with a large proportion of the samples exhibiting high inhibitory activities, indicative of potential bioactive natural products. Following bioassays, the most biologically active extracts were then fractionated using various chromatographic techniques, guided by biological evaluation each step of the process, dereplication performed using LC-HRMS, and bioactive compounds isolated using HPLC. Following purification, structure elucidation was conducted using high-resolution mass spectrometry (LC-HRMS). Chemical profiling was further aided by use of Global Natural Products Social Molecular Networking (GNPS) platform, alongside one-dimensional (1D) and two-dimensional (2D) nuclear magnetic resonance (NMR) techniques. Three compounds from the antibiofilm, and two compounds from the anti-acetylcholinesterase active fractions have been isolated and structures fully characterised using mass spectrometry and NMR, and confirmed by computer assisted structure elucidation (CASE).