title: Activity of isosteviol lactone on mitochondrial metabolism.
abstract: Isosteviol lactone (LAC), a lactone derivative of the diterpenic acid isosteviol (ISO) was evaluated for its effect on the oxidative metabolism of mitochondria isolated from rat liver. In this model, LAC (1 mM) depressed the phosphorylation efficiency, as shown by the decreased respiratory control coefficient (RCC) and ADP/O ratio. LAC (1 mM) inhibited NADH oxidase (45%), succinate oxidase (34%) and promoted low-level inhibitions on succinate dehydrogenase (13%), succinate-cytochrome c oxide-reductase (23%), cytochrome c oxidase (10%), and NADH dehydrogenase (13%). Glutamate dehydrogenase was also a target for LAC, as it was 85% inhibited by 1 mM LAC. Cyclic voltammetry data showed that LAC, as well as ISO, does not undergo redox reactions under current experimental conditions. LAC (0.05-0.75 mM) inhibited the swelling dependent on the glutamate oxidation, 50% of the effect occurring at 0.5 mM LAC. Swelling supported by KNO(3) and valinomycin was also inhibited over all concentrations used of LAC and ISO, the effect being of a lower intensity for LAC, suggesting that the modification of the structure of ISO by lactonization diminished its interaction with the membrane. This could contribute to attenuation of the toxic effects described for ISO on mitochondrial function, such as those on respiratory chain enzymatic complexes and phosphorylating activity.
authors.affiliation: Departamento de Bioqui;mica, Universidade Federal do Paraná, C.P. 19046, Curitiba, Paraná, 81531-990, Brazil. mbmo@bio.ufpr.br
authors.forename: Welligton L
authors.initials: WL
authors.lastname: Braguini
authors.forename: Maria A Biazon
authors.initials: MA
authors.lastname: Gomes
authors.forename: Brás H
authors.initials: BH
authors.lastname: de Oliveira
authors.forename: Eva G S
authors.initials: EG
authors.lastname: Carnieri
authors.forename: Maria Eliane M
authors.initials: ME
authors.lastname: Rocha
authors.forename: Maria Benigna M
authors.initials: MB
authors.lastname: de Oliveira
mesh_terms: D000818:Animals; D004224:Diterpenes / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D045786:Diterpenes, Kaurane; D004563:Electrochemistry; D004579:Electron Transport / Q000187:drug effects; D004594:Electrophysiology; D006868:Hydrolysis; D066298:In Vitro Techniques; D007659:Ketones / Q000737:chemistry; D007783:Lactones / Q000737:chemistry / Q000494:pharmacology*; D008297:Male; D008930:Mitochondria, Liver / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism*; D008933:Mitochondrial Swelling / Q000187:drug effects; D010084:Oxidation-Reduction; D010085:Oxidative Phosphorylation / Q000187:drug effects; D010101:Oxygen Consumption / Q000187:drug effects; D011506:Proteins / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D036625:Stevia / Q000737:chemistry; D013329:Structure-Activity Relationship
chemical_list: D004224:Diterpenes; D045786:Diterpenes, Kaurane; D007659:Ketones; D007783:Lactones; D011506:Proteins; C474284:isosteviol lactone; C012042:steviol