title: Differential and stereoselective in vitro cytotoxicity of eremophilane sesquiterpenes of Petasites hybridus rhizomes in rat hepatocytes.
abstract: We tested two CO (2) extracts of Petasites hybridus L. rhizomes, A (rich in furanoeremophilanes) and B (rich in petasins), for IN VITRO cytotoxicity in rat hepatocytes by means of the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay (EC (50) values of 0.64 mg/mL for A and 0.32 mg/mL for B). Eight eremophilane sesquiterpene lactones (SL) (1- 8) and one petasin (9) isolated from A were nontoxic or showed moderate cytotoxicity. The presence and type of the ester side chain most probably control the extent of cytotoxicity of the eremophilanolides. (8 R)-2-[(angeloyl)oxy]eremophil-7(11)-en-12,8-olide (1) damaged the hepatocytes most. The 8 α-stereoisomers of both 8-H epimeric couples of the 2-angeloyloxy- and 2-methacroyloxy-esters seem to be more cytotoxic (up to approx. 10-fold) than the corresponding 8 β-H stereoisomers. Moreover, the results of the MTT assay depended on the cell density being more pronounced with both 8 α-stereoisomers. Further investigations were conducted to study the influence of the stereochemistry on cell respiration, energy metabolism, and membrane integrity [release of lactate dehydrogenase (LDH)] with both couples of the 2-angeloyloxy- and 2-methacroyloxy-esters. In the LDH-leakage assay, (8 R)-2-[(methacroyl)oxy]eremophil-7(11)-en-12,8-olide (2) was the most toxic eremophilane. The stereoselectivity of cell damage of some SL points to a specific, yet unidentified molecular cytotoxicity target.
authors.affiliation: Institute of Pharmaceutical Sciences - Pharmacognosy, Karl-Franzens University of Graz, Graz, Austria.
authors.forename: Antje
authors.initials: A
authors.lastname: Bodensieck
authors.forename: Frank
authors.initials: F
authors.lastname: Gaunitz
authors.forename: Rolf
authors.initials: R
authors.lastname: Gebhardt
authors.forename: Ulrich
authors.initials: U
authors.lastname: Danesch
authors.forename: Rudolf
authors.initials: R
authors.lastname: Bauer
mesh_terms: D000818:Animals; D002462:Cell Membrane / Q000187:drug effects; D019069:Cell Respiration / Q000187:drug effects; D003603:Cytotoxins / Q000737:chemistry / Q000302:isolation & purification / Q000633:toxicity*; D004734:Energy Metabolism / Q000187:drug effects; D022781:Hepatocytes; D009281:Naphthalenes / Q000737:chemistry / Q000302:isolation & purification / Q000633:toxicity*; D036901:Petasites / Q000737:chemistry*; D000081223:Polycyclic Sesquiterpenes; D051381:Rats; D027343:Rhizome / Q000737:chemistry; D012717:Sesquiterpenes / Q000737:chemistry / Q000302:isolation & purification / Q000633:toxicity*; D013778:Tetrazolium Salts; D013844:Thiazoles
chemical_list: D003603:Cytotoxins; D009281:Naphthalenes; D000081223:Polycyclic Sesquiterpenes; D012717:Sesquiterpenes; D013778:Tetrazolium Salts; D013844:Thiazoles; C018286:eremophilane compounds; C022616:thiazolyl blue