title: Antimicrobial monomeric and dimeric diterpenes from the leaves of Helichrysum tenax var tenax.
abstract: The hexane extract of fresh air-dried leaves of Helichrysum tenax (Asteraceae) afforded ent-beyer-15-en-19-ol (1), its 4-epimer ent-beyer-15-en-18-ol (2), 15beta,16beta-epoxide-ent-beyeran-19-ol (3), as well as (4) consisting of two units of (1) linked as a diester of malonic acid, and (5), a compound. Its constituents are (1) and (3) also linked as a diester of malonic acid. The leaves of the plant are densely covered in fine glandular trichomes. These are extremely sticky and exude a mixture of the above diterpenes. Antimicrobial tests showed that (1), in particular, was highly active (3.1 and 3.6 microg/ml) against Bacillus cereus and Staphylococcus epidermidis, respectively.
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: K Esther
authors.initials: KE
authors.lastname: Mudau
authors.forename: Sandy F
authors.initials: SF
authors.lastname: van Vuuren
authors.forename: Alvaro M
authors.initials: AM
authors.lastname: Viljoen
mesh_terms: D000890:Anti-Infective Agents / Q000494:pharmacology*; D001409:Bacillus cereus / Q000187:drug effects; D019281:Dimerization; D004224:Diterpenes / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D004952:Esters / Q000737:chemistry / Q000494:pharmacology; D005658:Fungi / Q000187:drug effects*; D036562:Helichrysum / Q000737:chemistry*; D008314:Malonates / Q000737:chemistry / Q000494:pharmacology; D008826:Microbial Sensitivity Tests; D010936:Plant Extracts / Q000737:chemistry / Q000494:pharmacology; D018515:Plant Leaves / Q000737:chemistry*; D010946:Plants, Medicinal; D013212:Staphylococcus epidermidis / Q000187:drug effects
chemical_list: D000890:Anti-Infective Agents; D004224:Diterpenes; D004952:Esters; D008314:Malonates; D010936:Plant Extracts; C030290:malonic acid