The antileishmanial activity of lapachol, isolapachol, and dihydrolapachol, along with soluble derivatives (potassium salt) and acetate was obtained. All the compounds were assayed against metacyclic promastigotes of two different species of Leishmania associated to tegumentar leishmaniasis: L. amazonensis and L. braziliensis. All compounds presented significant activity, being isolapachol acetate the most active against promastigotes, with IC50/24h = 1.6 ± 0.0 µg/ml and 3.4 ± 0.5 µg/ml for, respectively, L. amazonensis and L. braziliensis. This compound was also assayed in vivo against L. amazonensis and showed to be active. Its toxicity in vitro was also established, and at concentration similar to the IC50, no toxicity was evidenced. In all experiments, pentamidine isethionate was used as a reference drug. The present results reinforce the potential use of substituted hydroxyquinones and derivatives as promising antileishmanial drugs and suggest a continuing study within this class of compounds.

Realizaram-se, com algumas 2-hidroxi-3-alquil-1,4-naftoquinonas, bioensaios para verificação de atividade moluscicida contra Biomphalaria glabrata, hospedeiro intermediário do Schistosoma mansoni. Estudos ciclovoltamétricos com algumas dessas mesmas substâncias, em meio aprótico, em N,N-dimetilformamida ou dimetilsulfóxido mais perclorato de tetrabutilamônio, em eletrodos de mercúrio e/ou carbono vítreo, foram, adicionalmente, desenvolvidos, visando à obtenção de informações úteis na elucidação do mecanismo biológico de ação. Várias das quinonas hidroxiladas apresentaram atividades moluscicidas significativas e a correlação entre tais atividades e os parâmetros eletroquímicos medidos, mostrou que o potencial de redução de primeira onda é um parâmetro importante para a atividade biológica. As quinonas mais facilmente redutíveis (>Ep1c) mostraram-se mais ativas frente ao molusco Biomphalaria glabrata, tanto na forma adulta como em massas de ovos, enquanto as 3-metilamino-2-hidroxinaftoquinonas, mais dificilmente redutíveis, não se mostraram ativas como agentes moluscicidas.

Several 2-hydroxy-3-alkyl-1,4-naphthoquinones have been submitted to molluscicidal bioassays against the snail Biomphalaria glabrata, intermediate host of Schistosoma mansoni. Cyclic voltammetric studies in aprotic medium (N,N-dimethylformamide plus tetrabutylammonium perchlorate) on Hg and glassy carbon electrodes have been performed on these compounds in order to obtain information about their biological mechanism of action. Several of the quinones assayed showed significant molluscicidal activities, and correlation of their activities and electrochemical parameters showed that the first wave reduction potential is an important parameter. The easily reduced quinones (>Ep1c) were more active against adult snails and against their egg masses, whilst the 3-methylamino-2-hydroxy derivatives presented higher negative reduction potentials and were not active as molluscicides.