No abstract

The labdane diterpenes copalic acid, 3β-acetoxy-copalic acid, 3β-hydroxy-copalic acid and ent-agathic acid were isolated from Copaifera langsdorffii oleoresin. These four compounds were submitted to structural modifications by reduction with hydrogen/palladium, esterification with diazomethane, esterification with methanol/sulfuric acid and conversion into sodium salt, furnishing 15 compounds. All compounds were assayed in vitro against Mycobacterium tuberculosis (H37Rv, ATCC 27294). The four compounds displayed minimum inhibitory concentration (MIC) value of 125 µg mL -1 , and were not considered active. A methylated derivative of compound 3β-hydroxy-copalic acid, and a sodium salt of copalic acid displayed MIC values of 25 µg mL -1 (71.7 µM) and 6.25 µg mL -1 (19.2 µM), respectively. The sodium salt of copalic acid stood out by displaying similar activity in comparison with streptomycin (MIC 6.25 µg mL -1) and a better activity compared to µM value of pyrazinamide (MIC 3.12 µg mL -1 ; 25.34 µM). Therefore, the methylated derivative of compound 3β-hydroxy-copalic acid and the sodium salt of copalic acid should be considered for further studies.

Recebido em 23/5/12; aceito em 21/8/12; publicado na web em 15/10/12Four goyazensolide-type sesquiterpene lactones -lychnofolide, centratherin, goyazensolide and goyazensolide acetate -were thoroughly studied by NMR experimental techniques.

Kaurenoic acid derivatives were prepared and submitted to in vitro assays with the fungus Colletotrichum lindemuthianum, which causes anthracnose disease in the common bean. The most active substances were found to be methyl and p-bromobenzylesters, 7 and 9, respectively, of the hydrogenated kaurenoic acid, which presented a minimum inhibitory concentration (MIC) of 0.097 and 0.131 mM, respectively, while the commercial fungicide methyl thiophanate (MT) presented a MIC of 0.143 mM. Substances 7 (1.401 mM) and 9 (1.886 mM) reduced the severity of anthracnose in common bean to values statistically comparable to MT (2.044 mM). According to an in silico study, both compounds 7 and 9 are inhibitors of the ketosteroid isomerase (KSI) enzyme produced by other organisms, the amino acid sequence of which could be detected in fungal genomes. These substances appeared to act against C. lindemuthianum by inhibiting its KSI. Therefore, substances 7 and 9 are promising for the development of new fungicides.

The solvent has a significant influence in the rate of reactions promoted by Stryker's reagent. The reactions performed in THF were, in most cases, faster than in toluene.