Indole Alkaloids from Chaetomium globosum

J Nat Prod. 2015 Jul 24;78(7):1479-85. doi: 10.1021/np5007235. Epub 2015 Jun 30.

Abstract

Two new indole alkaloids chaetocochin J (1) and chaetoglobinol A (8), along with chetomin (2), chetoseminudin A (3), cochliodinol (9), and semicochliodinol (10), were isolated from the rice culture of the fungus Chaetomium globosum. Their structures were elucidated by spectral analysis. Three new epipolythiodioxopiperazines, chaetocochins G-I (5-7), were identified by the combination of UPLC and mass spectrometric analysis. Chaetocochin I contained two sulfur bridges, one formed by three sulfur atoms between C-3 and C-11a, and the other formed by four sulfur atoms between C-3' and C-6'. Chaetocochin I was readily transformed into chetomin (2), chetoseminudin A (3), chaetocochin D (4), chaetocochin G (5), and chaetocochin H (6) by losing sulfur atoms. Compounds 1-3, and 8 exhibited antibacterial activities against Bacillus subtilis with MICs of 25, 0.78, 0.78, and 50 μg/mL, respectively, but not against Gram-negative bacterium (Escherichia coli). Compounds 2 and 8 were inactive against Candida albicans, Fusarium graminearum, Fusarium vasinfectum, Saccharomyces cerevisiae, and Aspergillus niger even at the high concentrations of 200 and 100 μg/mL, respectively. Compound 8 showed free radical scavenging capacity against the 1,1-diphenyl-2-picryl-hydrazyl (DPPH) and 2,2'-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid radical (ABTS(+•)), with IC50 values of 143.6 and 45.2 μM, respectively. The free radical scavenging capacity rates of compounds 1-3 on the DPPH and ABTS(+•) were less than 20% at the test concentrations (89.9-108.3 μM). The superoxide anion radical scavenging assay indicated that compounds 1-3, and 8 showed 14.8% (90.9 μM), 18.1% (90.9 μM), 51.5% (88.3 μM), and 30.4% (61.3 μM) superoxide anion radical scavenging capacity, respectively.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Anti-Bacterial Agents / chemistry
  • Anti-Bacterial Agents / isolation & purification*
  • Anti-Bacterial Agents / pharmacology
  • Bacillus subtilis / drug effects
  • Benzothiazoles / pharmacology
  • Biphenyl Compounds / pharmacology
  • Chaetomium / chemistry*
  • Escherichia coli / drug effects
  • Indole Alkaloids / chemistry
  • Indole Alkaloids / isolation & purification*
  • Indole Alkaloids / pharmacology
  • Microbial Sensitivity Tests
  • Molecular Structure
  • Nuclear Magnetic Resonance, Biomolecular
  • Oryza / growth & development
  • Oryza / microbiology
  • Picrates / pharmacology
  • Piperazines
  • Sulfonic Acids / pharmacology

Substances

  • Anti-Bacterial Agents
  • Benzothiazoles
  • Biphenyl Compounds
  • Indole Alkaloids
  • Picrates
  • Piperazines
  • Sulfonic Acids
  • chaetocochin J
  • chaetoglobinol A
  • 2,2'-azino-di-(3-ethylbenzothiazoline)-6-sulfonic acid
  • 1,1-diphenyl-2-picrylhydrazyl