Peptaibols from two unidentified fungi of the order Hypocreales with cytotoxic, antibiotic, and anthelmintic activities

Abstract

As part of an ongoing investigation of filamentous fungi for anticancer leads, an active culture was identified from the Mycosynthetix library (MSX 70741, of the order Hypocreales, Ascomycota). The fungal extract exhibited cytotoxic activity against the H460 (human non-small cell lung carcinoma) cell line, and bioactivity-directed fractionation yielded peptaibols 1–12 and harzianums A (13) and B (14). Structure elucidation of 1–12 was facilitated by high-resolution MS/MS obtained on a Thermo LTQ Orbitrap XL using Higher-Energy Collisional Dissociation (HCD) and by high field NMR (950 MHz). The absolute configuration was determined by Marfey’s analysis of the individual amino acids; the time required for such analysis was decreased via the development of a 10 min UPLC method. The isolated peptaibols (1–12), along with three other peptaibols isolated and elucidated from a different fungus (MSX 57715) of the same Order (15–17), were examined for activity in a suite of biological assays, including those for cytotoxic, antibacterial, and anthelmintic activities.

Unique amalgamation of primary and secondary structural elements transform peptaibols into potent bioactive cell-penetrating peptides

“…Alamethicin, an archetypical peptaibol, was eightfold less potent than 1 against PANC-1 cells (SI Appendix, Table S19). This agrees with widely reported cytotoxic properties described for most known peptaibols (18)(19)(20)(21)(22)(23)(24)(25). To provide an overall better understanding of the antiproliferative and cytotoxic properties of 1, the 10 helix is shown that was generated with Φ-and Ψ-angles of −49°and −29°for poly-Ala dodecamer using the PepMake 1.2 server at pepmake.wishartlab.com/.…”

“…The peptaibols have been intensively studied because of their abilities to form pores in the outer membranes of cells; these pore-forming capabilities result in most compounds in this class exhibiting nonspecific cytotoxic properties toward bacterial, fungal, and mammalian cells (15,17). The effects of peptaibols on mammalian cells tend to be relatively modest, causing the loss of cell viability at concentrations in the mid-to-high micromolar range (18)(19)(20)(21)(22)(23)(24)(25). With many hundreds of peptaibols reported, finding new peptaibol analogs that possess an alternative mode of biological activity would be an impracticable prospect if one relied solely on either chemically driven or genome-based approaches to identify candidate molecules.…”

“…The resulting products were purified, structurally characterized, and tested for cytotoxicity to gain further insights into the relationships between the primary and secondary structural features of the gichigamins and their biological properties. Nine major products were obtained (24)(25)(26)(27)(28)(29)(30)(31)(32) from the hydrolysis of 1 (SI Appendix, Fig. S3A) and ECD spectra were collected and analyzed for each compound (SI Appendix, Fig.…”

“…The mechanism of cell cytotoxicity induced by the peptaibols has been extensively studied and it has been consistently demonstrated that their abilities to induce cell death are related to their pore-forming capabilities (18)(19)(20)(21)(22)(23)(24)(25). Considering the increased potencies and unique structural features of the gichigamins, we first investigated whether these peptaibols incorporate into membranes to form pores.…”

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).…”