Antimicrobial acylphloroglucinols and dibenzyloxy flavonoids from flowers of Helichrysum gymnocomum

• Published in: Phytochemistry (Oxford) 2008-05, Vol.69 (8), p.1745-1749
• Main Authors: Drewes, Siegfried E., van Vuuren, Sandy F.
• Format: Article
• Language: English
• Subjects: acylphloroglucinol; Acylphloroglucinols; Anti-Infective Agents - chemistry; Anti-Infective Agents - pharmacology; antibacterial properties; antifungal properties; Antimicrobial; Biological and medical sciences; Chemical constitution; chemical structure; flavonoids; Flavonoids - chemistry; Flavonoids - pharmacology; Flowers; Flowers - chemistry; Fundamental and applied biological sciences. Psychology; Helichrysum; Helichrysum - chemistry; Helichrysum gymnocomum; Italy; Magnetic Resonance Spectroscopy; Microbial Sensitivity Tests; Molecular Structure; Phloroglucinol - analogs & derivatives; Phloroglucinol - chemistry; Phloroglucinol - pharmacology; phytochemicals; Plant cytology, morphology, systematics, chorology and evolution; Plant physiology and development; spectral analysis; Spermatophyta; Systematics (diagnosis, chromosome numbers)
• ISSN: 0031-9422; 1873-3700
• DOI: 10.1016/j.phytochem.2008.02.022

Four flavonoids and two acylphloroglucinols from Helichrysum gymnocomum are described. Two of the flavonoids are new in Nature and one of acylphloroglucinols is reported for the first time. The six compounds have MIC values below 64 μg/ml against a selection of ten pathogens. From the dichloromethane extract of the flowers of Helichrysum gymnocomum (Asteraceae) two known flavonoids, 4 and 5, and a known acylphloroglucinol, 3B, were isolated. In addition to 1 and 2, the 4′,6′-dibenzyloxy-2′-hydroxy derivative of 2′,4′,6′-trihydroxychalcone and 5,7-dibenzyloxy derivative of pinocembrin, respectively, are reported in Nature for the first time. A compound 3A, related to 3B has the structure 2-methyl-1-[2,4,6-trihydroxy-3-(2-hydroxy-3-methyl-3-butenyl)phenyl]-1-propanone. Compounds 1, 2, 3A, 3B, 4 and 5 have MIC values below 64 μg/ml against a selection of pathogens, with 3B having the highest sensitivity (6.3–45 μg/ml) for eight of the ten pathogens tested, including Staphylococcus aureus (6.3 μg/ml) and methicillin and gentamycin resistant strain of S. aureus (7.8 μg/ml). With the exception of 2, the other compounds had notable activity (45–63 μg/ml) towards Pseudomonas aeruginosa.