Cytotoxic and DNA-topoisomerase effects of lapachol amine derivatives and interactions with DNA

The cytotoxic activity of amino (3a-e), aza-1-antraquinone (4a-e) lapachol derivatives against Ehrlich carcinoma and human K562 leukemia cells was investigated. Cell viability was determined using MTT assay, after 48 (Ehrlich) or 96 h (K562) of culture, and vincristine (for K562 leukemia) and quercetin (for Ehrlich carcinoma) were used as positive controls. The results showed dose-dependent growth-inhibiting activities and that the amino derivatives were active against the assayed cells, whereas the 4a-e derivatives were not. The allylamine derivative 3a was the most active against Ehrlich carcinoma, with IC50 = 16.94 ± 1.25 muM, and against K562 leukemia, with IC50 = 14.11 ± 1.39 muM. The analogous lawsone derivative, 5a, was also active against Ehrlich carcinoma (IC50 = 23.89 ± 2.3 muM), although the 5d and 5e derivatives showed lower activity. The interaction between 3a-d and calf thymus DNA was investigated by fluorimetric titration and the results showed a hyperchromic effect indicating binding to DNA as presented of ethidium bromide, used as positive control. The inhibitory action on DNA-topoisomerase II-a was also evaluated by a relaxation assay of supercoiled DNA plasmid, and the etoposide (200 muM) was used as positive control. Significant inhibitory activities were observed for 3a-d at 200 muM and a partial inhibitory action was observed for lapachol and methoxylapachol.

Chronic administration of caffeine: effect on the activities of hepatic antioxidant enzymes of Ehrlich ascites tumor-bearing mice.

Chronic ingestion (for 22-30 consecutive days) of caffeine (20 mg/kg/day, p.o.) increased the activities of the hepatic enzymes- catalase (CAT) and superoxide dismutase (SOD) and decreased its lipid peroxidation (LP) in mice. Development of Ehrlich ascites carcinoma (EAC) cell decreased the activities of hepatic CAT and SOD and increased LP. But pretreatment of caffeine for 12 consecutive days and continuation of its treatment during the course of development of EAC cells restored the EAC cell-induced changes in liver CAT, SOD and LP to their corresponding control values. Thus, the present results by confirming the results of others previously published, suggest that caffeine is an antioxidant and may act as an anticarcinogen.