Melokhanines A-J, Bioactive Monoterpenoid Indole Alkaloids with Diverse Skeletons from Melodinus khasianus

J Nat Prod. 2016 Sep 23;79(9):2158-66. doi: 10.1021/acs.jnatprod.6b00011. Epub 2016 Sep 1.

Abstract

The new melokhanines A-J (1-10) and 22 known (11-32) alkaloids were isolated from the twigs and leaves of Melodinus khasianus. The new compounds and their absolute configurations were elucidated by extensive analysis of spectroscopic, X-ray diffraction, and computational data. Melokhanine A (1), composed of a hydroxyindolinone linked to an octahydrofuro[2,3-b]pyridine moiety, is an unprecedented monoterpenoid indole alkaloid. Melokhanines B-H (2-8) possess a new 6/5/5/6/6 pentacyclic indole alkaloid skeleton. Alkaloids 1-16, 25-27, 31, and 32 showed the best antibacterial activity against Pseudomonas aeruginosa (MIC range 2-22 μM). Among the seven dermatophytes tested, compound 1 showed significant inhibitory activity against Microsporum canis, M. ferrugineum, and Trichophyton ajelloi (MIC range 38-150 μM), i.e., half the efficacy of the positive control, griseofulvin.

MeSH terms

  • Apocynaceae / chemistry*
  • Crystallography, X-Ray
  • Drug Screening Assays, Antitumor
  • Drugs, Chinese Herbal / chemistry*
  • Drugs, Chinese Herbal / isolation & purification
  • Drugs, Chinese Herbal / pharmacology*
  • Escherichia coli / drug effects
  • Griseofulvin / pharmacology
  • Microbial Sensitivity Tests
  • Microsporum / drug effects
  • Molecular Conformation
  • Molecular Structure
  • Nuclear Magnetic Resonance, Biomolecular
  • Plant Leaves / chemistry
  • Plant Stems / chemistry
  • Pseudomonas aeruginosa / drug effects
  • Secologanin Tryptamine Alkaloids / chemistry*
  • Secologanin Tryptamine Alkaloids / isolation & purification
  • Secologanin Tryptamine Alkaloids / pharmacology*
  • Trichophyton / drug effects

Substances

  • Drugs, Chinese Herbal
  • Secologanin Tryptamine Alkaloids
  • melokhanine A
  • Griseofulvin