Antistaphylococcal Prenylated Acylphoroglucinol and Xanthones from Kielmeyera variabilis

• Published in: Journal of natural products (Washington, D.C.) Vol. 79; no. 3; pp. 470 - 476
• Main Authors: Coqueiro, Aline, Choi, Young H, Verpoorte, Robert, Gupta, Karthick B. S. S, De Mieri, Maria, Hamburger, Matthias, Young, Maria C. M, Stapleton, Paul, Gibbons, Simon, Bolzani, Vanderlan da S
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society and American Society of Pharmacognosy 25.03.2016
• Subjects: Anti-Bacterial Agents - chemistry; Anti-Bacterial Agents - isolation & purification; Anti-Bacterial Agents - pharmacology; Brazil; Clusiaceae - chemistry; Methicillin-Resistant Staphylococcus aureus - drug effects; Microbial Sensitivity Tests; Molecular Structure; Nuclear Magnetic Resonance, Biomolecular; Phloroglucinol - analogs & derivatives; Phloroglucinol - chemistry; Phloroglucinol - isolation & purification; Phloroglucinol - pharmacology; Plant Components, Aerial - chemistry; Staphylococcus aureus - drug effects; Stereoisomerism; Xanthones - chemistry; Xanthones - isolation & purification; Xanthones - pharmacology; Brazil
• ISSN: 0163-3864; 1520-6025
• DOI: 10.1021/acs.jnatprod.5b00858

Bioactivity-guided fractionation of the EtOH extract of the branches of Kielmeyera variabilis led to the isolation of a new acylphoroglucinol (1), which was active against all the MRSA strains tested herein, with pronounced activity against strain EMRSA-16. Compound 1 displayed an MIC of 0.5 mg/L as compared with an MIC of 128 mg/L for the control antibiotic norfloxacin. The structure of the new compound was elucidated by 1D and 2D NMR spectroscopic analysis and mass spectrometry, and experimental and calculated ECD were used to determine the absolute configurations. The compounds β-sitosterol (2), stigmasterol (3), ergost-5-en-3-ol (4), and osajaxanthone (5) also occurred in the n-hexane fraction. The EtOAc fraction contained nine known xanthones: 3,6-dihydroxy-1,4,8-trimethoxyxanthone (6), 3,5-dihydroxy-4-methoxyxanthone (7), 3,4-dihydroxy-6,8-dimethoxyxanthone (8), 3,4-dihydroxy-2-methoxyxanthone (9), 5-hydroxy-1,3-dimethoxyxanthone (10), 4-hydroxy-2,3-dimethoxyxanthone (11), kielcorin (12), 3-hydroxy-2-methoxyxanthone (13), and 2-hydroxy-1-methoxyxanthone (14), which showed moderate to low activity against the tested MRSA strains.