title: Inhibitory effects against pasture weeds in Brazilian Amazonia of natural products from the marine brown alga Dictyota menstrualis.
abstract: Fractions of the acetone extract and a mixture of two diterpenes from the marine brown alga Dictyota menstrualis were prepared with the aim of identifying potential effects on the germination of seeds and on elongation of the radicle and hypocotyl of the weeds Mimosa pudica and Senna obtusifolia. The bioassay on seed germination was performed in controlled conditions of 25 degreeC temperature and a 12 hour photoperiod, while the one concerning radicle and hypocotyl elongation was performed at the same temperature, though adopting a photoperiod of 24 hours. The results varied according to the receptor species, the fraction utilized, and its concentration. TLC analysis of the fractions and comparison with isolated products indicated that the diterpenes pachydictyol A and isopachydictyol A were the most abundant compounds in fraction HE, whereas the diterpene 6-hydroxy-dichotomano-2, 13-diene-16, 17-dial (3) was the most abundant compound in fractions DC and EA. Analysis of less polar fractions (in n-hexane, dichloromethane and ethyl acetate) revealed values of less than 30% inhibition. On the other hand, the ethanol/water fraction was the most active in all instances. The biological activity of these fractions must be due to the presence of known diterpenes and/or sulfated polysaccharides isolated in earlier studies.
authors.affiliation: Programa de Pós-Graduação em Química, Instituto de Química, Universidade Federal Fluminense, Niterói, RJ, 24020-150, Brazil.
authors.forename: Rainiomar Raimundo
authors.initials: RR
authors.lastname: Fonseca
authors.affiliation: Lab. Agroindústria, EMBRAPA Amazônia Oriental/ CPATU, Belém, Pará, 66095-100, Brazil
authors.forename: Antonio Pedro Silva Souza
authors.initials: AP
authors.lastname: Filho
authors.affiliation: Departamento de Biologia Marinha, Instituto de Biologia, P.O. Box 100.644, Niterói, RJ, 24001-970, Brazil.
authors.forename: Roberto Campos
authors.initials: RC
authors.lastname: Villaça
authors.affiliation: Departamento de Biologia Marinha, Instituto de Biologia, P.O. Box 100.644, Niterói, RJ, 24001-970, Brazil.
authors.forename: Valéria Laneuville
authors.initials: VL
authors.lastname: Teixeira
mesh_terms: D001938:Brazil; D004224:Diterpenes / Q000633:toxicity; D018525:Germination / Q000187:drug effects; D006540:Herbicides / Q000302:isolation & purification*; D031298:Mimosa / Q000187:drug effects; D000459:Phaeophyceae / Q000737:chemistry*; D057685:Plant Weeds / Q000187:drug effects; D029846:Senna Plant / Q000187:drug effects
chemical_list: D004224:Diterpenes; D006540:Herbicides