14-Residue peptaibol velutibol A from Trichoderma velutinum: its structural and cytotoxic evaluation.

Varun Pratap Singh,Manoj Kushwaha,Vandana Sharma,Deepika Singh,Fayaz A Malik,Inshad A Khan,Anil Kumar,Anup Singh Pathania,Ram A Vishwakarma,Samsher Singh

doi:10.1039/d0ra05780k

Abstract

Velutibol A (1), a new 14-residue peptaibol was isolated from the Himalayan cold habitat fungus Trichoderma velutinum. The structural characterization was carried out by 1D and 2D NMR studies, and tandem mass studies, and Marfey's method aided in determining the stereochemistry of the amino acids. The CD analysis revealed folding of the peptide in a 310-helical conformation. The intramolecular H-bonding was determined by an NMR-VT experiment. Cytotoxic evaluation was carried out against a panel of cancer cell lines. The cell cycle assay was carried out on human myeloid leukaemia (HL-60) cells and revealed the formation of apoptotic bodies and DNA damage in a dose-dependent manner. Three other peptaibols namely velutibol B (2), velutibol C (3), and velutibol D (4) were also isolated in trace amounts from the psychotropic fungus and characterized through tandem mass spectroscopy and Marfey's analysis.

Highlights

Peptaibols belong to the class of non-ribosomal peptides comprising non-proteinogenic amino acid residues including aaminoisobutyric acid (Aib), ethyl norvaline, isovaline, hydroxylproline etc
The close observation of 1D carbon NMR experiments including 13C and DEPT spectra revealed 69 carbon signals, which were assigned for 15 carbonyls, 6 carbons (a,a-disubstituted carbon), 12 methines, 15 methylene and 21 methyl carbons (Table 1) (Fig. S5–S8, Electronic supplementary information (ESI)†)
The respective amino acid derivatives were found to be in-line with the extracted ion chromatogram (EIC) obtained for compounds 2–4 (Fig. S28–S33, ESI†)

Summary

Introduction

Peptaibols belong to the class of non-ribosomal peptides comprising non-proteinogenic amino acid residues including aaminoisobutyric acid (Aib), ethyl norvaline, isovaline, hydroxylproline etc. The MS/MS data in combination with the NOESY and HMBC correlations established the sequence of compound 1 as Ac-Aib-Gln-Leu-Aib-Pro-Val-Leu-Aib-Pro-Aib- The advanced Marfey's analysis carried out for 1 indicated the L-form of Glu/Gln, Leu, Val, Pro and Leuol (Fig. S14, ESI†).

Results

Conclusion