RESUMO
The major compound responsible for toxicity to Artemia salina of some Fusarium tricinctum strains has been isolated, and its structure has been elucidated by spectroscopical methods, i.e. UV, IR, MS, 1H-NMR and 13C-NMR. The novel compound, trivially named visoltricin, is the first imidazole derivative produced by Fusarium spp., and its structure has been established as the methyl ester of 3-[1-methyl-4-(3-methyl-2-butenyl)-imidazol-5yl]-2-propenoic acid (molecular formula C13H18N2O2; MW = 234.297). Visoltricin was toxic to A. salina larvae (LD50 = 8.5 x 10(-7) M), and inhibited the growth of six human tumour cell lines (out of 60 lines tested) at concentrations lower than 10(-5) M. Tested on rabbit eye it showed an interesting miotic activity similar to that of pilocarpine, a miotic agent largely used in the therapy of glaucoma. This biological activity could be explained in part by the anticholinesterase properties shown by visoltricin towards both human serum and pure enzymes (EC 3.1.1.7 and EC 3.1.1.8). Kinetics studies showed for visoltricin a mixed-type and reversible inhibition of the EC 3.1.1.7 enzyme with the competitive inhibition constant (Ki) = 1.9 x 10(-4) M.
Assuntos
Fusarium/química , Ácido Urocânico/análogos & derivados , Animais , Artemia/efeitos dos fármacos , Divisão Celular/efeitos dos fármacos , Humanos , Dose Letal Mediana , Mióticos/farmacologia , Coelhos , Células Tumorais Cultivadas , Ácido Urocânico/química , Ácido Urocânico/isolamento & purificação , Ácido Urocânico/toxicidadeRESUMO
Isoguanine (2) was found to be an antineoplastic constituent of Prioneris thestylis Dbldy. wings. Three other purine components of the butterfly wings were identified as hypoxanthine (3), uric acid (4) and xanthine (5). Isolation of urocanic acid (6) from the same wing material represented the first detection of this interesting histidine derivative in an arthropod.
