Safety evaluation of certain food additives - ipcs inchem

ALKOXY-SUBSTITUTED ALLYLBENZENES 375
P = 0.04). Chewers with a SULT1A1 Arg-Arg and GSTP1 Val-Val/Ile-Val genotype
(4.6 ng/mg creatinine) and non-chewers with either SULT1A1 Arg-His or GSTP1
Ile-Ile genotypes (4.7 ng/mg creatinine) had a moderately increased 8-OH-dG level.
Thus, the susceptible SULT1A1 and GSTP1 genotypes may modulate increased
DNA oxidative stress elicited by betel quid chewing (Wong et al., 2008).
The cytotoxic and genotoxic potentials of methyl eugenol, safrole, eugenol
and isoeugenol were evaluated using cultured primary hepatocytes isolated from
male Fischer 344 rats and female B6C3F1 mice. Lactate dehydrogenase (LDH)
release was used to assess cytotoxicity, whereas the UDS assay was used to
assess genotoxicity. Rat and mouse hepatocytes showed similar patterns of toxicity
for each chemical tested. Methyl eugenol and safrole were relatively non-cytotoxic
but caused UDS at concentrations between 10 and 500 μmol/l. In contrast,
isoeugenol and eugenol produced cytotoxicity in hepatocytes with median lethal
concentration (LC50) values of approximately 200–300 μmol/l, but did not cause
UDS. Concurrent incubation of cyclohexane oxide, an epoxide hydrolase
competitor, at 2000 μmol/l with a non-cytotoxic concentration of methyl eugenol
(10 μmol/l) resulted in increased cytotoxicity but had no effect on genotoxicity.
However, incubation of pentachlorophenol, a SULT inhibitor, at 15 μmol/l with
10 μmol methyl eugenol/l resulted in increased cytotoxicity and significantly reduced
genotoxicity. These results suggest that methyl eugenol is similar to safrole in its
ability to cause cytotoxicity and genotoxicity in rodents. It appears that the
bioactivation of methyl eugenol to a DNA-reactive electrophile is mediated by a
SULT in rodents, but epoxide formation is not responsible for the observed
genotoxicity (Burkey et al., 2000).
The cytotoxic and apoptotic effects of myristicin on the human
neuroblastoma SK-N-SH cells were evaluated. A dose-dependent reduction in cell
viability occurs at a myristicin concentration of 0.5 mmol/l in SK-N-SH cells.
Apoptotic cell death was monitored using DNA fragmentation, terminal deoxyribonucleotidyl
transferase–mediated 2-deoxyuridine-5-triphosphate (dUTP) nick-end
labelling and 4,6-diamidino-2-phenylindole staining. The apoptosis triggered by
myristicin was accompanied by an accumulation of cytochrome c and by the
activation of caspase-3. The results obtained suggest that myristicin induces
cytotoxicity in human neuroblastoma SK-N-SH cells by an apoptotic mechanism
(Lee et al., 2005).
2.1.6 Protein adducts
The dose-related formation of protein adducts has been indirectly related to
observed hepatotoxicity in studies with safrole, estragole and methyl eugenol in
rodents. In repeated oral dose studies in rats, low doses (10 or 30 mg/kg bw per
day for 5 days) of methyl eugenol have been shown to produce a single 44 kilodalton
(kDa) microsomal protein adduct; the protein adduct is likely formed from the
reaction of the electrophilic 1-hydroxylation metabolite (carbonium ion) with a
precursor to the 67 kDa laminin receptor, which is a peripheral membrane
glycoprotein involved in tumour cell invasion and metastasis (Gardner et al., 1997b).
At higher dose levels (100 and 300 mg/kg bw per day), this protein adduct is also
the major product, but as many as 20 other protein adducts are formed. The