title: Phytotoxic activity in Flourensia campestris and isolation of (--)-hamanasic acid A as its active principle compound.
abstract: An aqueous extract from Flourensia campestris (Asteraceae) dry aerial parts showed strong inhibition on the germination and growth of Lactuca sativa. Based on bio-guided chromatographic fractionation of aq. extracts from dry and fresh leaves and spectroscopic means, (-)-hamanasic acid A (7-carboxy-8-hydroxy-1(2), 12(13)-dien-bisabolene (1)) was isolated as the most inhibitory active principle on germination (ECg(50)=2.9 mM) and on root (ECr(50)=1.5 mM)/shoot (ECs(50)=2.0 mM) growth. As measured by GC, and correlated with a simple designed 2D-TLC, compound 1 was distributed throughout the plant, with a remarkably high concentration (1.6%) in the leaves and the inflorescences. At least a quarter of the amount of 1 was found in aqueous extracts suggesting that leaching would be a key route for its release into the environment. By contrast, leaf essential oils (HD) between 0.5 and 1.5 μl ml(-1) did not show herbicidal effects and 1 was not found in them (TLC) nor among volatiles (HS-SPME). Volatile compositions were assessed by GC-FID and GC-MS and led to the identification of 23 compounds (4 monoterpenes and 19 sesquiterpenes) with a wide seasonal (spring-summer%) variation, represented principally by bicyclo-germacrene (37-6%), spathulenol (4-32%), globulol (20-0%), beta-caryophyllene (15-6%), caryophyllene oxide (1-13%) and bicycloelemene (10-1%), respectively. The high amount of 1 in F. campestris together with its feasibility of being extracted with water suggest that (-)-hamanasic acid A is an allelochemical in this species. Species-specific studies must be carried out to evaluate the potential of 1 as a natural herbicidal compound.
authors.affiliation: Estación de Biología Sierras, Universidad de Buenos Aires, Casilda S/N, Huerta Grande 5174, Córdoba, Argentina.
authors.forename: Mariana P
authors.initials: MP
authors.lastname: Silva
authors.forename: Leonardo A
authors.initials: LA
authors.lastname: Piazza
authors.forename: Daniela
authors.initials: D
authors.lastname: López
authors.forename: Marisa J
authors.initials: MJ
authors.lastname: López Rivilli
authors.forename: Mauricio D
authors.initials: MD
authors.lastname: Turco
authors.forename: Juan J
authors.initials: JJ
authors.lastname: Cantero
authors.forename: Mónica G
authors.initials: MG
authors.lastname: Tourn
authors.forename: Ana L
authors.initials: AL
authors.lastname: Scopel
mesh_terms: D019659:Asteraceae / Q000737:chemistry*; D005591:Chemical Fractionation; D002849:Chromatography, Gas; D018525:Germination / Q000187:drug effects; D018545:Lactuca / Q000187:drug effects* / Q000254:growth & development; D018517:Plant Roots / Q000187:drug effects / Q000254:growth & development; D018520:Plant Shoots / Q000187:drug effects / Q000254:growth & development; D012717:Sesquiterpenes / Q000737:chemistry / Q000302:isolation & purification / Q000633:toxicity*
chemical_list: C577211:7-carboxy-8-hydroxy-1(2),12(13)-dien-bisabolene; D012717:Sesquiterpenes