Acetophenone derivatives from a freshwater fungal isolate of recently described Lindgomyces madisonensis (G416)

Abstract

The exploration of freshwater ascomycetes, which have undergone only limited investigation, may provide opportunities both to characterize new genera/species of fungi and to uncover new chemical diversity. In this study, seven acetophenone derivatives, madisone, 4'-methoxymadisone, dehydromadisone, 2″-methoxymadisone, dihydroallovisnaginone, dimadisone, and 4'-methoxydimadisone were characterized from an organic extract of a recently described Lindgomyces madisonensis (G416) culture, which was isolated from submerged wood collected in a stream in North Carolina. Madisone, dehydromadisone, 2″-methoxymadisone, dimadisone and 4'-demethoxydimadisone have not been reported previously, while 4'-methoxymadisone and dihydroallovisnaginone were previously unknown as natural products. Their structures were assigned on the basis of NMR and HRESIMS data, with the structure of madisone supported by X-ray crystallography. The antimicrobial activities of madisone, 4'-methoxymadisone and dihydroallovisnaginone were evaluated against a panel of bacteria and fungi. A heat map analysis of the surface of a G416 culture showed that most of the isolated compounds concentrated in the guttate compared with the vegetative mycelium of the fungus.

Enhanced dereplication of fungal cultures via use of mass defect filtering

“…As mentioned previously, G600 was determined to biosynthesize 17 ; G416, on the other hand, was known to produce mainly polyketides. 40 The co-culture was analyzed, and the resulting mass defect profile was compared with separate cultures of G600 and G416 (Figure 5). As expected, 17 was identified and appeared to be the most abundant in both G600 and in the co-culture (Supplementary Figure S7).…”

Prealamethicin F50 and related peptaibols from Trichoderma arundinaceum: validation of their authenticity via in situ chemical analysis

“…The droplet-LMJ-SSP is a manually controlled surface sampling tool that performs a microextraction on the culture surface. The droplet-LMJ-SSP has been used in various types of analysis of fungal cultures, including the in situ scouting and identification of peptaibols, 19 dereplication 18 and mapping of the spatial and temporal distribution of fungal metabolites, 20, 21 and to monitor the biosynthesis of targeted non-natural natural products. 22 …”

In situ mass spectrometry monitoring of fungal cultures led to the identification of four peptaibols with a rare threonine residue

“…D or L). Given the ability to study peptaibols by mass spectrometry, coupled with their interesting biological activities (Figueroa et al, 2013; He et al, 2006; Schiell et al, 2001; Thirumalachar, 1968), we sought to study fungal cultures in situ toward the discovery of peptaibols by using the droplet–LMJ–SSP, (Kertesz and Van Berkel, 2010; Paguigan et al, 2016; Sica et al, 2016b; Sica et al, 2015; Sica et al, 2016c). The fungal culture, coded MSX53554, which was identified as Nectriopsis Maire (Bionectriaceae), was readily noted as a peptaibol producer based on the mass spectral data (Figure 1).…”

“…These small peptides have been reported to possess a wide variety of bioactivities, such as antimicrobial (Figueroa et al, 2013), anthelmintic (Schiell et al, 2001; Thirumalachar, 1968), and cytotoxic (He et al, 2006). As part of a multidisciplinary program to identify new anticancer leads from nature (Ayers et al, 2012; Figueroa et al, 2013; Kinghorn et al, 2016), a protocol was implemented to monitor the chemistry of fungal cultures in situ using a recently described droplet–liquid microjunction–surface sampling probe (droplet–LMJ–SSP) coupled to an ultraperformance liquid chromatography–high resolution mass spectrometry (UPLC–HRMS) system (Kertesz and Van Berkel, 2010; Paguigan et al, 2016; Sica et al, 2016b; Sica et al, 2015; Sica et al, 2016c). …”

“…This system is designed to perform microextractions on the surface of a sample and directly inject the extract into LC-MS (Kertesz and Van Berkel, 2010, 2013, 2014). Recently, this technique has been applied towards in situ analyses of fungal and plant metabolites with various goals, such as dereplication of fungal cultures (Sica et al, 2015), spatial and temporal mapping of the biosynthesis of targeted leads in fungal cultures (Paguigan et al, 2016; Sica et al, 2016b; Sica et al, 2016c), and the characterization of complex mixtures in a suite of plant tissues (Sica et al, 2016a). A major benefit of this technique is the ability to monitor the biosynthesis of fungal secondary metabolites, both with respect to space and time, without having to extract the entire culture.…”