CNFD (6b,7-dihydro-5H-cyclopenta[b]naphtho[2,1-d]furan-5,6(9aH)-dione) is a semisynthetic naphthoquinone derived from lawsone that has cytotoxic action in different tumor lines and anticancer activity in vivo. Therefore, this molecule is a relevant candidate for drug development, but there is still no information on its human metabolism and systemic elimination. This study aimed to investigate the in vitro metabolism of this naphthoquinone by human liver microsomes. Initially, in order to determine the in vitro enzymatic kinetic parameters, a high performance liquid chromatography (HPLC) method to quantify the CNFD was developed and validated. In addition, the enzymatic kinetic data, the predicted pharmacokinetic in vivo parameters and the phenotyping study were presented. The main metabolism sites and metabolites have been suggested in silico. The developed HPLC method was linear, reproducible, selective, accurate, and stable. The enzymatic kinetic parameters revealed a sigmoidal profile. In vitro to in vivo extrapolation hepatic metabolic clearance was 10.39 mL min-1 kg-1 protein and the liver extraction rate was 51%. The clearance in vivo associated with a hepatic extraction ratio indicates that the hepatic metabolism is the main route of elimination. Although all cytochrome P450 enzymes evaluated metabolized CNFD, CYP2C9 and CYP3A4 showed higher metabolic capacity. For the first time, metabolism studies of CNFD were demonstrated.

AbstractIn Amazonas State (Brazil), Justicia acuminatissima (Miq.) Bremek., Acanthaceae, leaf teas are used in folk medicine to treat several inflammatory illnesses. In order to validate this medicinal application, we analyzed the acute toxicity and antioxidant, antiedematogenic and antinociceptive potentials of an aqueous extract of this species, using culture cells and animal models. The aqueous extract did not cause toxic effects on human lymphocytes in high concentration (400 μg/ml), neither on mice treated with high doses (5000 mg/kg) in an acute toxicity analysis by oral route, and also did not cause lesions in the gastric mucosa of animals treated with 300 mg/kg, which was the maximal dose used in the anti-inflammatory screening. The aqueous extract caused inhibition of inflammatory pain in formalin-induced paw licking test with all tested doses, 30, 100 and 300 mg/kg, and antiedematogenic activity at 100 and 300 mg/kg. Additionally, the aqueous extract presented statistically significant action on the release of nitric oxide by lipopolysaccharide-activated macrophages. These results and other preliminary studies support the folk use of this species, and further investigation of its action mechanism by inhibition of COX-2 or related metabolite would be interesting.