53330-02-2Relevant academic research and scientific papers
Inhibition of human leukaemia 60 cell growth by mercapturic acid metabolites of phenylethyl isothiocyanate
Adesida,Edwards,Thornalley
, p. 385 - 392 (1996)
Mercapturic acid pathway metabolites of phenylethyl isothiocyanate inhibited the growth of human leukaemia 60 (HL60) cells in vitro. The adduct with L-cysteine, S-(N-phenylethylthiocarbamoyl)cysteine, was the most potent with strong antileukaemic activity: the median growth inhibitory concentration (GC50) value was 336 ± 1 nM (N = 18) compared with GC50 values of the precursor formed from dietary glucosinolates, phenylethyl isothiocyanate, 1.49 ± 0.01 μM (N = 8), and the initial mercapturic acid pathway metabolite S-(N-phenylethylthiocarbamoyl)glutathione 5.46 ± 0.36 μM (N = 18). S-(N-Benzylthiocarbamoyl)cysteine and S-(N-phenylpropylthiocarbamoyl)cysteine also had antiproliferative activity but S-(N-phenylethylthiocarbamoyl)cysteine was the most potent compound studied. The latter induced DNA fragmentation in HL60 cells but DNA laddering characteristic of apoptosis was not observed. It had low toxicity to corresponding differentiated cells, neutrophils, in culture, and therefore the cytotoxicity had selectivity for leukaemia cells. The antiproliferative activity of S-(N-phenylethylthiocarbamoyl)cysteine was lost during preincubation with culture medium, attributed to S-thiocarbamoyl transfer to serum proteins, which may decrease its effectiveness in vivo. The antiproliferative activity of S-(N-phenylalkylthiocarbamoyl)cysteine derivatives, by inhibiting tumour growth in pre-clinical development, may contribute to the association of decreased cancer incidence with dietary glucosinolate consumption.
Inhibition of N-nitrosodimethylamine demethylase in rat and human liver microsomes by isothiocyanates and their glutathione, L-cysteine, and N- acetyl-L-cysteine conjugates
Jiao, Ding,Clifford Conaway,Wang, Mong-Heng,Yang, Chung S.,Koehl, Werner,Chung, Fung-Lung
, p. 932 - 938 (1996)
Natural and synthetic isothiocyanates and their conjugates were examined for their inhibitory effects toward rat and human liver microsomal N-dimethylnitrosoamine demethylase (NDMAd) activity using a radiometric NDMAd assay. Substrate concentrations of 30 and 60 μM were used to probe the activity of cytochrome P4502E1 isozyme through the α-hydroxylation of NDMA. It was found that alkyl isothiocyanates such as sulforaphane and allyl isothiocyanate displayed very weak inhibition, whereas the arylalkyl isothiocyanates such as benzyl and phenethyl isothiocyanate showed significant inhibition toward rat liver NDMAd activity with IC50 values of 9.0 and 8.3 μM, respectively. More interestingly, glutathione conjugates of benzyl, phenethyl, and 6-phenylhexyl isothiocyanates all inhibited NDMAd at the comparable concentrations. In the phenethyl isothiocyanate conjugates series, there exist marked differences in their inhibitory activity; i.e., its conjugates with L-cysteine (IC50 = 4.3 μM) and with glutathione (IC50 = 4.0 μM) are more potent than its conjugate of N-acetylcysteine (IC50 = 24.0 μM). The same trend was also observed for the human liver microsomal NDMAd activity. The half-lives of these conjugates were determined in the presence of other free thiols from L-cysteine or glutathione using an HPLC system. It was shown that isothiocyanates are released from their conjugates and react with the free thiols present in the solution. The longer half-life of N-acetylcysteine conjugate of phenethyl isothiocyanate as compared to the other conjugates is consistent with its lower inhibitory activity. The inhibition of NDMAd, and therefore cytochrome P4502E1, by isothiocyanate conjugates is most likely due to the action of the free isothiocyanates released from the conjugates. Since cytochrome P4502E1 and other isozymes play important roles in the activation of the tobacco-specific nitrosoamines, these results provide a basis for investigating the potential of isothiocyanate conjugates as chemopreventive agents.
