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.
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.