Three new labdanes isolated from Eragrostis viscosa

Three new labdanes with 8α,15-epoxy ring [methyl 8α,15-epoxylabdan-16β-oate, 8α,15-epoxylabdan-16β-ol and 8α,15-epoxy-16-norlabdan-13β-ol] and five known compounds [8α,15-epoxy-16-norlabdan-13-one, 8α,15-epoxylabdan-16β-oic acid, 3β-(3'',4''-dihydroxy)(E)-cinnamoyloxylup-20(29)-ene, 3-(2',3',4',6'-tetra-O-acetyl-β-D-glucopyranosyloxy)β-sitosterol and 16-acetoxy-8α,15-epoxylabdane] were isolated from toluene and dichloromethane extracts of aerial parts of Eragrostis viscosa. The structures of all the compounds were established based on their spectroscopic data and X-ray diffraction analysis of 8α,15-epoxylabdan-16β-ol. It was also studied the genotoxicity of E. viscosa, particularly compounds 16-acetoxy-8α, 15-epoxylabdane, 8α,15-epoxy-16-norlabdan-13-one and 8α, 15-epoxilabdan-16β-ol, using a cytokinesis-block micronucleus assay and the Ames test to assess mutagenicity. Both assays were negative. Cytotoxicity was also analyzed using an MTT assay, and 8α,15-epoxy-16β-ol was shown to be the most cytotoxic of the compounds tested. E. viscosa extracts were also tested to determine their antioxidant capacities, peroxide values and total phenolic contents.
Três novos labdanos com anel 8α,15-epoxi [8α,15-epoxilabdan-16β-oato de metila, 8α,15-epoxilabdan-16β-ol e 8α,15-epoxi-16-norlabdan-13β-ol] e cinco compostos conhecidos [8α,15-epoxi-16-norlabdan-13-ona, ácido 8α,15-epoxilabdan-16β-oico, β-(3’’,4’’-di-hidroxi)- (E)-cinamoiloxilup-20(29)-eno, 3-(2’,3’,4’,6’-tetra-O-acetil-β-D-glucopiranosiloxi)-β-sitosterol e 16-acetoxi-8α,15-epoxilabdano] foram isolados dos extratos de tolueno e diclorometano de partes aéreas da Eragrostis viscosa. A estrutura dos compostos foi atribuída a partir dos seus dados espectroscópicos e da análise de difração de raios X do 8α,15-epoxilabdan-16β-ol. Os compostos 16-acetóxi-8α,15-epoxilabdano, 8α,15-epoxi-16-norlabdan-13-ona e 8α,15-epoxilabdan-16β-ol não apresentam genotoxicidade e mutagenicidade, as quais foram avaliadas usando o teste dos micronúcleos e o teste de Ames, respetivamente. A citotoxicidade dos mesmos compostos foi avaliada usando o teste do MTT sendo o 8α,15-epoxilabdan-16β-ol o mais citotóxico de todos os compostos analisados. Foram também avaliadas a capacidade antioxidante, o valor peróxido e o conteúdo em fenóis totais de extratos de E. viscosa.