4-Hydroxy-3-methyl-2(1 H )-quinolone, originally discovered from a Brassicaceae plant, produced by a soil bacterium of the genus Burkholderia sp.: determination of a preferred tautomer and antioxidant activity

• Published in: Beilstein journal of organic chemistry 2020-06, Vol.16 (1), p.1489-1494
• Main Authors: Li, Dandan, Oku, Naoya, Shinozaki, Yukiko, Kurokawa, Yoichi, Igarashi, Yasuhiro
• Format: Article
• Language: English
• Subjects: antioxidant; Antioxidants; Bacteria; Brassicaceae; Burkholderia; burkholderia sp; Chemiluminescence; Chemistry; Endangered & extinct species; Fermentation; Fungi; Gram-negative bacteria; Hydrocarbons; Immune response; Letter; Metabolites; NMR; Nuclear magnetic resonance; quinolone; Reactive oxygen species; soil bacterium; Soil microorganisms; Zinc; zn2+ enrichment culture
• ISSN: 1860-5397; 2195-951X; 1860-5397
• DOI: 10.3762/bjoc.16.124

4-Hydroxy-3-methyl-2(1 )-quinolone ( ), a molecule known for a long time and recently discovered from a plant without providing sufficient evidence to support the structure, was isolated from a fermentation extract of sp. 3Y-MMP isolated from a soil by a Zn enrichment culture. Detailed spectroscopic analyses by MS and NMR, combined with C chemical shift comparison with literature values of the related compounds and a synthetic preparation of , allowed its first full NMR characterization and identification of 2-quinolone but not 2-quinolinol ( ) as the preferred tautomer for this heterocyclic system. While the metal-chelating activity was negligible, compound at 10 μM, a concentration lower than that in liquid production cultures, quenched hydroxy radical-induced chemiluminescence emitted by luminol by 86%. Because some species are pathogenic to plants and animals, the above result suggests that is a potential antioxidant to counteract reactive oxygen species-based immune response in the host organisms.