Synthesis, biological evaluation, and structure-activity relationships of dithiolethiones as inducers of cytoprotective phase 2 enzymes

Dithiolethiones are a family of promising cancer chemopreventive agents, and induction of phase 2 enzymes is key to their chemopreventive activities. Two dithiolethiones have been evaluated in humans for cancer prevention. While some chemopreventive activities were detected in several human studies, potential side effects are a concern. Herein, we report structure-activity relationships of 25 dithiolethiones. Several compounds show exceedingly potent and bladder specific activity in phase 2 enzyme induction. Structural features responsible for such activity, as well as those inhibiting the activity, are discussed. Moreover, the compounds activate and depend on Nrf2 for their inductive activities. Nrf2 is a major transcriptional stimulator of cytoprotective genes and is critical for cancer prevention. Thus, several new dithiolethiones that are highly promising for bladder cancer prevention have been identified. Because the compounds act specifically in the bladder, the likelihood of potential systemic toxicity may be low.

log P Estimation of 1,2-Dithiole-3-thiones and 1,2-Dithiole-3-ones: A Comparison of Experimental and Calculative Approaches

PURPOSE

To estimate experimental log P values of formerly described 5-formyl- and 5-acyl-dithiole-3-thiones (DTT) and -dithiole-3-ones (DTO) and to check the validity of five log P calculation programs via experimental log P for a database of 68 DTT and DTO.

METHODS

Experimental log P values were measured by means of octanol/water partitioning; for determining solute concentrations in water, RP-HPLC with spectrophotometric detection was used. For calculating log P, the fragmental methods ACD/log P, CLOGP, and KOWWIN, the atom-based approach XLOGP, and the whole-molecule approach QLOGP were applied.

RESULTS

Quality of calculations significantly differs depending on the subset under consideration. For database compounds 01-48, comprising alkyl and aryl substitution in 4- and 5-position, the fragmental methods ACD/log P, CLOGP, and KOWWIN perform significantly better than the atom-based approach XLOGP and the whole-molecule method QLOGP. For database compounds 49-68, comprising formyl and acyl substitution in 4- and 5-position, superiority of the whole-molecule method QLOGP over the substructure-based approaches is observed. The strong underestimation of log P for compounds 49-68 probably indicates hidden physicochemical phenomena resulting from the juxtaposition of the acyl and dithiole moieties.

CONCLUSIONS

All calculation methods included in this study need a thorough refinement to adequately cope with particular solvation behavior suspected to prevail in formyl- or acyl-DTT and DTO, which represent a chemical class of high pharmacological interest.

On the reduction of dithiolethiones and dithiolylium ions by NADPH and glutathione reductase

Results of in vitro experiments carried out in water at 25 degrees C and at pH 7.56 proved that NADPH in the presence of yeast glutathione reductase did not react with 1,2-dithiole-3-thiones and 1,2-dithiole-3-ones. On the other hand, 3-methylthiodithiolylium ions did react in these conditions. The reaction was identified and methyl 3-mercaptopropenedithioate resulting from a two-electron reduction process was obtained. A kinetic scheme consisting in a biordered mechanism has been found (Km = 2.6 10(-5) mol x l(-1)). All these results raise the question of a possible in vivo methylation (or alkylation) of dithiolethiones occurring prior to any other reductive biochemical process they may undergo. They also raise the question of the very existence (or in any case the generalization) of a reductive metabolism of dithiolethiones.