The in vitro toxicity of nitrile and epithionitrile derivatives of glucosinolates from swedes (Brassica napus) in human and bovine liver cells

ABSTRACT

Aim

To investigate the direct in vitro toxicity in human and bovine liver cells, and inhibition of activity of ATP-binding cassette transporter G2 (ABCG2) and cytochrome P450 3A4 (CYP3A4) by five nitrile and epithionitrile derivatives from swede (Brassica napus).

Methods

The following compounds were investigated: 1-cyano-2-hydroxy-3-butene (CHB, epithionitrile derivative of progoitrin), 1-cyano-2-hydroxy-3,4-epithiobutane (epithionitrile derivative of progoitrin), 3-butenenitrile (nitrile from sinigrin), 4-pentenenitrile (nitrile from gluconapin), and 5-hexenenitrile (nitrile from glucobrassicanapin). Direct cytotoxicity was assessed by incubating the compounds (at 100 mM, 200 mM, 2 M) with human (HepG2) hepatocellular carcinoma cells or bovine primary hepatocytes for 24 hours. Cell viability was then assessed using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Cytotoxicity in Hep2G cells was also assessed after incubation for 72 hours at sub-chronic concentrations (1, 2.5, 5, 10, 15, 20 µM) and for combinations of compounds (20 µM). The ability of compounds to inhibit activity of the ABCG2 transporter and the CYP3A4 enzyme were assessed using human ABCG2 vesicles and demethylation of erythromycin by rat liver microsomes, respectively.

Results

No reduction of cell viability compared to control assays was observed when the tested compounds were incubated with Hep2G cells or bovine liver cells at concentrations up to 2 mM for 24 hours or with Hep2G cells at concentrations up to 20 µM for 72 hours. None of the five tested compounds inhibited the ability of the ABCG2 transporter to transport the fluorescent substrate at concentrations up to 2 mM. Furthermore, no inhibition of CYP3A4 activity (measured as N-demethylation of erythromycin) was observed for CHB up to 2 mM.

Conclusion

This study suggests that under these conditions, the selected nitrile or epithionitrile derivatives of glucosinolates are not hepatotoxic in vitro.

KEYWORDS:

• Glucosinolate
• epithionitrile
• nitrile
• Brassica
• bovine
• ABCG2
• liver toxicity

Correction Statement

This article has been republished with minor changes. These changes do not impact the academic content of the article.

Acknowledgements

All studies were conducted and analysed by IL and RC under the direct supervision of BC, the lead author and researcher for this article. Samples of glucosinolate-derived compounds were generously provided by Dr Mark Collett of the School of Veterinary Science at Massey University (NZ). The study was funded by a grant from AGMARDT.

Notes

1 K.Greish, University of Otago, Dunedin, NZ