title: Antimicrobial acylphloroglucinols and dibenzyloxy flavonoids from flowers of Helichrysum gymnocomum.
abstract: 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 64microg/ml against a selection of pathogens, with 3B having the highest sensitivity (6.3-45microg/ml) for eight of the ten pathogens tested, including Staphylococcus aureus (6.3microg/ml) and methicillin and gentamycin resistant strain of S. aureus (7.8microg/ml). With the exception of 2, the other compounds had notable activity (45-63microg/ml) towards Pseudomonas aeruginosa.
authors.affiliation: School of Chemistry, University of KwaZulu-Natal, Private Bag X01, Scottsville, 3209 Pietermaritzburg, South Africa. drewes@ukzn.ac.za
authors.forename: Siegfried E
authors.initials: SE
authors.lastname: Drewes
authors.forename: Sandy F
authors.initials: SF
authors.lastname: van Vuuren
mesh_terms: D000890:Anti-Infective Agents / Q000737:chemistry* / Q000494:pharmacology; D005419:Flavonoids / Q000737:chemistry* / Q000494:pharmacology; D035264:Flowers / Q000737:chemistry*; D036562:Helichrysum / Q000737:chemistry*; D007558:Italy; D009682:Magnetic Resonance Spectroscopy; D008826:Microbial Sensitivity Tests; D015394:Molecular Structure; D010696:Phloroglucinol / Q000031:analogs & derivatives / Q000737:chemistry* / Q000494:pharmacology
chemical_list: D000890:Anti-Infective Agents; D005419:Flavonoids; D010696:Phloroglucinol