title: Phytotoxic activity and conformational analysis of thymol analogs from Hofmeisteria schaffneri.
abstract: Bioassay-guided fractionation of two phytotoxic extracts (a CH(2)Cl(2)-MeOH (1:1) and an aqueous) prepared from the aerial parts of Hofmeisteria schaffneri led to isolation of thymol analogs 3-5, along with seven known compounds, 1, 2 and 6-10. Compounds 3-5 were identified by spectroscopic methods as 1,4-bis(2'-hydroxy-4'-methylphenyl)butane-1,4-dione (3), 2-isopropyl-5-methylphenyl (2Z)-2-methylbut-2-enoate (4) and 2-hydroxy-2-(2-hydroxy-4-methylphenyl)propane-1,3-diyl (2Z,2'Z)bis(2-methylbut-2-enoate) (5) and designated trivial names of hofmeisterins II-IV, respectively. Their conformational behavior was also studied by molecular modeling using density functional theory calculations at the B3LYP/DGDZVP level. Compounds 1-4 and 6-10 significantly inhibited radicle growth of seedlings of Amaranthus hypochondriacus and Echinochloa crus-galli in the Petri dish bioassay with IC(50)'s10(-4)M. Furthermore, the northymol analog 3 provoked significant bleaching of seedlings of A. hypochondriacus. However, none of the isolates affected either seedling growth or germination of Medicago sativa.
authors.affiliation: Facultad de Química, Universidad Nacional Autónoma de México, México DF 04510, Mexico.
authors.forename: Araceli
authors.initials: A
authors.lastname: Pérez-Vásquez
authors.forename: Edelmira
authors.initials: E
authors.lastname: Linares
authors.forename: Robert
authors.initials: R
authors.lastname: Bye
authors.forename: Carlos M
authors.initials: CM
authors.lastname: Cerda-García-Rojas
authors.forename: Rachel
authors.initials: R
authors.lastname: Mata
mesh_terms: D019659:Asteraceae / Q000737:chemistry*; D006540:Herbicides / Q000737:chemistry* / Q000494:pharmacology*; D008958:Models, Molecular; D015394:Molecular Structure; D035261:Plant Components, Aerial / Q000737:chemistry; D012639:Seeds / Q000187:drug effects; D013943:Thymol / Q000031:analogs & derivatives* / Q000737:chemistry* / Q000494:pharmacology
chemical_list: D006540:Herbicides; D013943:Thymol