New naphthoquinones and an alkaloid with in vitro activity against Toxoplasma gondii RH and EGS strains

Exp Parasitol. 2012 Sep 18. pii: S0014-4894(12)00263-9. doi: 10.1016/j.exppara.2012.09.003. [Epub ahead of print]

New naphthoquinones and an alkaloid with in vitro activity against Toxoplasma gondii RH and EGS strains

Ferreira RA, Oliveira AB, Gualberto SA, Miguel Del Corral JM, Fujiwara RT, Guimarães PH, Vitor RW.

Laboratório de Microscopia, Instituto de Ciências Agrárias, Faculdade de Estudos Administrativos, FEAD, Brazil; Departamento de Parasitologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Brazil.

The efficacy of three amino-terpenyl naphthoquinones and the alkaloid liriodenine were examined against tachyzoites and tissues cysts of the RH and EGS strains, respectively. Monolayers of 2C4 fibroblasts infected with tachyzoites of the RH strain were incubated with different concentrations of the compounds for 48 hours. Specifically, 7-(4-methyl-3-pentenyl)-2-pyrrolidine-[1,4]-naphthoquinone (QUI-5), 6-(4-methyl-3-pentenyl)-2-pyrrolidine-[1,4]-naphthoquinone (QUI-6), 6-(4-methylpentyl)-2-pyrrolidine-[1,4]-naphthoquinone (QUI-11), and (8 h-benzo[g]-1,3-benzodioxolo[6,5,4-de]quinolin-8-one,9Cl-1,2-methylene dioxiaporfina (liriodenine) inhibited intracellular replication of T. gondii. The IC(50) values obtained for compounds QUI-5 and QUI-6 were 69.35 μM and 172.81 μM (i.e., 21.4 μg/mL and 53.4 μg/mL), respectively. The naphthoquinone QUI-11 and liriodenine significantly inhibited intracellular replication of T. gondii. The IC(50) values obtained with these experiments were 0.32 μM and 0.07 μM (i.e., 0.1 μg/mL and 0.02 μg/mL), respectively. Compounds QUI-5, QUI-6, QUI-11 and liriodenine demonstrated lower toxicity for 2C4 fibroblasts compared to atovaquone. In addition, cysts isolated from the brains of mice chronically infected with the EGS strain were exposed to the compounds. Infectivity of the cysts after incubation with the compounds was assessed by infection of mice. The data obtained showed that in vitro incubation with QUI-6, QUI-11 and liriodenine inhibited the infectivity of the bradyzoites. This activity was time- and concentration-dependent.

PMID: 23000485 [PubMed - as supplied by publisher]