Exploitation of Mangrove Endophytic Fungi for Infectious Disease Drug Discovery.

There is an acute need for new and effective agents to treat infectious diseases. We conducted a screening program to assess the potential of mangrove-derived endophytic fungi as a source of new antibiotics. Fungi cultured in the presence and absence of small molecule epigenetic modulators were screened against Mycobacterium tuberculosis and the ESKAPE panel of bacterial pathogens, as well as two eukaryotic infective agents, Leishmania donovani and Naegleria fowleri. By comparison of bioactivity data among treatments and targets, trends became evident, such as the result that more than 60% of active extracts were revealed to be selective to a single target. Validating the technique of using small molecules to dysregulate secondary metabolite production pathways, nearly half (44%) of those fungi producing active extracts only did so following histone deacetylase inhibitory (HDACi) or DNA methyltransferase inhibitory (DNMTi) treatment.

Chromatographic editing enhances natural product discovery.

Fungi are known for their diverse biologically active secondary metabolites, compounds that have provided the basis for many landmark therapeutics in the last century. Due to ease of collection and culturing, the existing fungal chemical literature is vast, and fungal natural product isolation can often be hindered by the numerous nuisance and pan-toxic compounds that many strains produce. Dereplication efforts, aimed at identifying such compounds early in the purification, are imperative to reduce time and expense of rediscovery of known metabolites. The common practice of dereplication then deprioritizes samples containing nuisance compounds and often excludes them from the drug discovery workflow. We have implemented a two-step dereplication protocol that uses tandem mass spectrometry to identify nuisance compounds, followed by mass-directed chromatographic editing to remove them while leaving the remaining 'edited extract' in the drug discovery workflow. This two-step strategy facilitates rapid and more accurate evaluation of the chemical potential of high-throughput extract screening campaigns by consideration of bioactivity beyond that triggered by known metabolites. We demonstrate the isolation of a new natural product antibiotic from an otherwise toxic extract using the technique.