M. Solfrizzo et A. Visconti, ANTICHOLINESTERASE ACTIVITY OF THE FUSARIUM METABOLITE VISOLTRICIN AND ITS N-METHYL DERIVATIVE, Toxicology in vitro, 8(3), 1994, pp. 461-465
Visoltricin is a bioactive 4,5-disubstituted N-methylimidazole produce
d by Fusarium tricinctum, which shows toxic activity towards Artemia s
alina larvae and miotic activity on rabbit eye. The anticholinesterase
properties and kinetic parameters of visoltricin and N-methyl visoltr
icin were assessed. Visoltricin anticholinesterase activity was demons
trated on human serum [median inhibitory concentration (IC50) = 2.6 x
10(-4) M], bovine erythrocyte acetylcholinesterase EC 3.1.1.7 (IC50 =
4 x 10(-4) M) and human serum cholinesterase EC 3.1.1.8 (IC50 = 1.9 x
10(-4) M). The acetylcholinesterase inhibition constants (K-i) of viso
ltricin and N-methyl visoltricin were 1.88 x 10(-4) M and 6.5 x 10(-5)
M, respectively. Kinetic studies showed for both compounds a mixed-ty
pe inhibition, with partial binding of the inhibitor to the enzyme-sub
strate complex. Visoltricin was a reversible inhibitor of acetylcholin
esterase, as it was not hydrolysed by the inhibited enzyme, and the in
hibition in vitro was concentration dependent but not time dependent.
The anticholinesterase activity could explain, at least in part, the m
iotic activity of visoltricin.