Dereplication of macrocyclic trichothecenes from extracts of filamentous fungi through UV and NMR profiles

Abstract

Macrocyclic trichothecenes, which have potent cytotoxicity, have been isolated from many different fungal species. These compounds were evaluated clinically by the U.S. National Cancer Institute in the 1970's and 1980's. However, they have yet to be advanced into viable drugs due to severe side effects. Our team is investigating a diverse library of filamentous fungi for new anticancer leads. To avoid re-isolating macrocyclic trichothecenes via bioactivity-directed fractionation studies, a protocol for their facile dereplication was developed. The method uses readily available photodiode array detectors to identify one of two types of characteristic UV spectra for these compounds. Also, diagnostic signals can be observed in the 1H-NMR spectra, particularly for the epoxide and conjugated diene moieties, even at the level of a crude extract. Using these techniques in a complementary fashion, macrocyclic trichothecenes can be dereplicated rapidly.

Chemoinformatic Expedition of the Chemical Space of Fungal Products

“…Based on previous studies and as part of our continued effort to quantify the chemical diversity of fungal isolates [6], herein we expand the analysis to a larger set of 207 compounds described by our group [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] that represent twice the size of the dataset analyzed in 2012. In the current analysis, we employed molecular fingerprints as distinct molecular representations not analyzed in the previous study; also we emphasized the evaluation of molecular complexity that may have a significant impact in drug discovery endeavors, since this feature has been associated with target selectivity (and potential toxicity).…”

“…The largest fragments were kept, duplicates in each dataset were removed and all molecules with molecular weight (MW) over 1000 were excluded. The in-house library of fungal metabolites with 207 compounds (referred to hereafter as 'FUNGI') [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] was compared with the following five reference collections: 2249 compounds based on the Flavor and Extract Manufacturers Association of the United States GRAS list, updated to GRAS 27 (hereafter referred to as 'GRAS') [24,30]; FDA drugs obtained from DrugBank [31] containing: 76 drugs approved to treat cancer (hereafter referred to as 'FDA-ONC') and 1399 nononcological drugs (hereafter referred to as 'FDA-NONC'); 713 drugs in clinical trials reported by the Therapeutic Target Database [32] (hereafter referred to as 'CLINIC'); and 850 compounds from a commercial collection focused on epigenetic targets, available at Selleckchem (hereafter referred to as 'GENERAL') [33]. Supplementary Table 1 summarizes the number of duplicate molecules found in the initial datasets.…”

High-Resolution MS, MS/MS, and UV Database of Fungal Secondary Metabolites as a Dereplication Protocol for Bioactive Natural Products

“…The resulting 10-min chromatographic method and associated high-resolution mass spectra could be used to discriminate between all the compounds in the database. Of these, only two resorcylic acid lactones, 7- epi -zeaenol and 15- O -desmethyl-5 Z -7-oxozeaenol, 30 did not ionize in the ESI + mode, whereas 17 compounds, mostly trichothecenes, 31 did not ionize in the ESI − mode (Table S1, Supporting Information). Also, the molecular ion peaks of aphidicolin and viridicatumtoxin were the only ones not detected in the positive-ion mode, due to the facile loss of H 2 O; however, the molecular ion peak for the latter was observed in the negative-ion mode.…”

Discovery of Anticancer Agents of Diverse Natural Origin

“…A major concentration in the work on fungi has been the development of procedures for secondary metabolite de-replication, to improve efficiency and avoid focusing resources on the re-identification of known compounds (51, 52). This includes the application of a new technique to analyze the chemistry of fungal cultures in situ via a droplet liquid micro-junction surface sampling probe, which has been utilized for our Program Project (53).…”