title: Biochemically active sesquiterpene lactones from Ratibida mexicana.
abstract: Bioactivity-directed fractionation of the methanol extract of the roots of Ratibida mexicana resulted in the isolation of two bioactive sesquiterpene lactones, isoalloalantolactone and elema-1,3,11-trien-8,12-olide. Both compounds caused a significant inhibition of the radicle growth of Amaranthus hypochondriacus and Echinochloa crus-galli, exerted moderate cytotoxic activity against three different solid tumour cell lines and inhibited significantly the radial growth of three phytopathogenic fungi. Isoalloalantolactone also caused the inhibition of ATP synthesis, proton uptake and electron transport (basal, phosphorylating and uncoupled) from water to methylviologen, therefore acting as a Hill's reaction inhibitor. The lactone did not affect photosystem I but inhibited photosystem II. The site of inhibition of isoalloalantolactone is located in the span of P680 to QA redox enzymes because the uncoupled electron transport from water to silicomolybdate and, from DPC to DCIP are inhibited approximately to the same extent.
authors.affiliation: Facultad de Química, Universidad Nacional Autónoma de México, México, D.F.
authors.forename: M R
authors.initials: MR
authors.lastname: Calera
authors.forename: F
authors.initials: F
authors.lastname: Soto
authors.forename: P
authors.initials: P
authors.lastname: Sanchez
authors.forename: R
authors.initials: R
authors.lastname: Bye
authors.forename: B
authors.initials: B
authors.lastname: Hernandez-Bautista
authors.forename: A L
authors.initials: AL
authors.lastname: Anaya
authors.forename: B
authors.initials: B
authors.lastname: Lotina-Hennsen
authors.forename: R
authors.initials: R
authors.lastname: Mata
mesh_terms: D000935:Antifungal Agents / Q000737:chemistry* / Q000302:isolation & purification / Q000494:pharmacology; D000972:Antineoplastic Agents, Phytogenic / Q000737:chemistry* / Q000302:isolation & purification / Q000494:pharmacology; D002470:Cell Survival / Q000187:drug effects; D002736:Chloroplasts / Q000187:drug effects / Q000378:metabolism; D005658:Fungi / Q000187:drug effects; D006801:Humans; D007783:Lactones / Q000737:chemistry* / Q000302:isolation & purification / Q000494:pharmacology; D019684:Magnoliopsida; D008826:Microbial Sensitivity Tests; D015394:Molecular Structure; D018517:Plant Roots; D010946:Plants, Medicinal; D012717:Sesquiterpenes / Q000737:chemistry* / Q000302:isolation & purification / Q000494:pharmacology; D018724:Spinacia oleracea; D013329:Structure-Activity Relationship; D014407:Tumor Cells, Cultured
chemical_list: D000935:Antifungal Agents; D000972:Antineoplastic Agents, Phytogenic; D007783:Lactones; D012717:Sesquiterpenes