RESUMO
The sesquiterpene lactone glaucolide B (1), isolated from Vernonia fruticulosa (Asteraceae), was transformed into six lactones (2-7). The structures of the products were elucidated by spectroscopic analysis. A series of solutions of compounds 1-7, at 200 microM, were tested on the germination and on the root and shoot growth of the dicotyledons Physalis ixocarpa and Trifolium alexandrinum and of the monocotyledons Lolium multiflorum and Amaranthus hypochondriacus. Lactone 5 exhibited clear selectivity towards dicotyledonous species at 200 microM, with an average inhibition of 90% on the germination of P. ixocarpa. Lactones 1, 3 and 4 had a greater effect on root length of monocotyledonous species, inhibiting around 70% at 200 microM in L. multiflorum. It seems that the diol function is required in lactones 4-6 to increase the activity, the polarity in the molecule might be required to reach its target.
Assuntos
Lactonas/isolamento & purificação , Extratos Vegetais/química , Sesquiterpenos/isolamento & purificação , Sesquiterpenos/farmacologia , Vernonia/química , Amaranthus/efeitos dos fármacos , Germinação/efeitos dos fármacos , Lactonas/química , Lactonas/farmacologia , Lolium/efeitos dos fármacos , Espectroscopia de Ressonância Magnética , Estrutura Molecular , Extratos Vegetais/isolamento & purificação , Raízes de Plantas/efeitos dos fármacos , Raízes de Plantas/crescimento & desenvolvimento , Brotos de Planta/efeitos dos fármacos , Brotos de Planta/crescimento & desenvolvimento , Sementes/efeitos dos fármacos , Sementes/fisiologia , Sesquiterpenos/química , Trifolium/efeitos dos fármacosRESUMO
In isolated spinach chloroplasts, low concentrations (I(50)=14 microM) of methyl trachyloban-19-oate ester inhibited ATP synthesis and coupled electron transport as well as light-activated membrane-bound Mg(2+)-ATPase activity. Basal (-Pi) and uncoupled electron transport and heat-activated Ca(2+)-dependent ATPase activity of isolated coupling factor proteins were unaffected by methyl trachyloban-19-oate. Thylakoids partially stripped of coupled factor by EDTA were unable to accumulate protons in the light. However, increasing concentrations of methyl trachyloban-19-oate ester restored this ability. It is concluded that the methyl trachyloban-19-oate ester effects result from blocking proton transport through the CF(0) channel. Methyl trachyloban-19-oate ester exhibited non-competitive kinetics with DCCD and triphenyltin. These results suggest that the natural products, DCCD and triphenyltin, access inhibition sites in CF(0). The K(i) is 75 microM.