title: Antiproliferative activity and new argininyl bufadienolide esters from the "cururú" toad Rhinella (Bufo) schneideri.
abstract: BACKGROUND
  Toads known as "cururú" (Rhinella schneideri) have been used in the Brazilian Pantanal and Paraguayan Chaco wetlands to treat erysipelas and cancer. The aim of the study was to assess the antiproliferative effect of the venom obtained from Rhinella schneideri and to identify its constituents by spectroscopic and spectrometric methods.
  
  
  METHODS
  The venom was obtained by gentle pressing the parotid glands of the toads. The dry crude drug was analyzed by HPLC-MS-MS and chromatographed on Sephadex LH-20 to obtain purified compounds and fractions for spectroscopic analysis. The venom and fractions were evaluated for antiproliferative activity towards normal human lung fibroblasts (MRC-5) and four human cancer cell lines: gastric epithelial adenocarcinoma (AGS), lung cancer (SK-MES-1), bladder carcinoma (J82) and promyelocytic leukemia (HL-60).
  
  
  RESULTS
  From the Rhinella schneideri venom, 29 compounds were isolated and/or identified by spectroscopic and spectrometric means. Three known alkaloids and five argininyl diacids were identified in the complex mixture by HPLC-MS-MS. Nine out of fifteen argininyl diacid derivatives of the bufadienolides bufalin, marinobufagin and telocinobufagin are reported for the first time and four argininyl diacids are described for the first time as natural products. The venom and the fractions 9-13 showed a remarkable antiproliferative effect, with IC50 values in the range 0.019-0.022, 0.035-0.040, 0.028-0.064, 0.042-0.056 and 0.044-0.052 µg/mL for MRC-5, AGS, SK-MES-1, J82 and HL-60 cell lines, respectively. Under the same experimental conditions, IC50 values of the reference compound etoposide were 2.296, 0.277, 1.295, 1.884 and 1.059 µg/mL towards MRC-5, AGS, SK-MES-1, J82 and HL-60 cells, respectively.
  
  
  CONCLUSIONS
  The venom showed a strong antiproliferative effect towards human cancer cells and presented a high chemical diversity in its constituents, supporting its use as anticancer agent. These findings encourage further work on the chemistry and bioactivity of South American toad venoms.
authors.affiliation: Laboratorio de Química de Productos Naturales, Instituto de Química de Recursos Naturales, Universidad de Talca, Casilla 747, 3460000 Talca, Chile. Electronic address: schmeda@utalca.cl.
authors.forename: Guillermo
authors.initials: G
authors.lastname: Schmeda-Hirschmann
authors.affiliation: Laboratorio de Química de Productos Naturales, Instituto de Química de Recursos Naturales, Universidad de Talca, Casilla 747, 3460000 Talca, Chile.
authors.forename: Cristina
authors.initials: C
authors.lastname: Quispe
authors.affiliation: Laboratorio de Cultivo Celular, Facultad de Ciencias de la Salud, Universidad de Talca, Casilla 747, 3460000 Talca, Chile.
authors.forename: Cristina
authors.initials: C
authors.lastname: Theoduloz
authors.affiliation: Laboratório de Pesquisa em Química de Produtos Naturais, Departamento de Química, Universidade Federal de Mato Grosso, Av. Fernando C. da Costa s/n, 78060-900 Cuiabá, Mato Grosso, Brazil; Instituto Nacional de Ciência e Tecnologia em Áreas Úmidas (INAU), Rua Nove, 305, Boa Esperanca, 78068-410 Cuiabá, Mato Grosso, Brazil.
authors.forename: Paulo Teixeira
authors.initials: PT
authors.lastname: de Sousa
authors.affiliation: Laboratório de Pesquisa em Química de Produtos Naturais, Departamento de Química, Universidade Federal de Mato Grosso, Av. Fernando C. da Costa s/n, 78060-900 Cuiabá, Mato Grosso, Brazil; Instituto Nacional de Ciência e Tecnologia em Áreas Úmidas (INAU), Rua Nove, 305, Boa Esperanca, 78068-410 Cuiabá, Mato Grosso, Brazil.
authors.forename: Carlos
authors.initials: C
authors.lastname: Parizotto
mesh_terms: D000664:Amphibian Venoms / Q000737:chemistry*; D000818:Animals; D000970:Antineoplastic Agents / Q000008:administration & dosage / Q000302:isolation & purification / Q000494:pharmacology; D001938:Brazil; D002018:Bufanolides / Q000008:administration & dosage / Q000302:isolation & purification / Q000494:pharmacology*; D002025:Bufonidae; D002460:Cell Line; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects*; D002851:Chromatography, High Pressure Liquid; D004354:Drug Screening Assays, Antitumor; D004952:Esters; D005347:Fibroblasts / Q000187:drug effects* / Q000378:metabolism; D018922:HL-60 Cells; D006801:Humans; D020128:Inhibitory Concentration 50; D009369:Neoplasms / Q000188:drug therapy / Q000473:pathology; D010239:Paraguay; D053719:Tandem Mass Spectrometry
chemical_list: D000664:Amphibian Venoms; D000970:Antineoplastic Agents; D002018:Bufanolides; D004952:Esters
keywords: Antiproliferative activity; Argininyl bufadienolides; Brazilian pantanal; Bufo; Rhinella schneideri