Safety evaluation of certain food additives - ipcs inchem

FURAN-SUBSTITUTED ALIPHATIC HYDROCARBONS 519
(a) In vitro
In standard Salmonella mutagenicity assays, 2,5-dimethylfuran (No. 1488),
3-methyl-2-(3-methylbut-2-enyl)-furan (No. 1494), 3-(2-furyl)acrolein (No. 1497),
4-(2-furyl)-3-buten-2-one (No. 1511), ethyl 3-(2-furyl)propanoate (No. 1513) and
O-ethyl S-(2-furylmethyl)thiocarbonate (No. 1526) were not mutagenic in
Salmonella typhimurium strains TA97, TA98, TA100, TA102, TA1535, TA1537 or
TA1538 when tested at concentrations of up to 10 000 μg/plate, alone or in the
presence of an exogenous rat liver metabolic activation system (S9) (Wild et al.,
1983; Mortelmans et al., 1986; Shinohara et al., 1986; Asquith, 1989; Eder et al.,
1991; Zeiger et al., 1992; Lee et al., 1994; Verspeek-Rip, 2000). Likewise, with the
exception of a single assay in which equivocal results of mutagenicity were reported
in S. typhimurium strains TA97 and TA107 (Zeiger et al., 1992), 2-methylfuran
(No. 1487) was consistently negative in several other strains of S. typhimurium (i.e.
TA98, TA100, TA102 and TA1535) both alone and with an exogenous rat liver
bioactivation system (S9) (Shinohara et al., 1986; Aeschbacher et al., 1989).
Evaluated alone and with an exogenous bioactivation system in S. typhimurium at
concentrations of up to 0.660 μmol/plate (54.2 μg/plate), 2-furyl methyl ketone (No.
1503) exhibited a significant positive mutagenic potential only in strain TA98 with
bioactivation at the two lower concentrations (i.e. 0.165 and 0.330 μmol/plate)
(Shinohara et al., 1986). At higher concentrations, significant cytotoxicity was
observed, which was reflected by a concentration-dependent decrease in the
number of revertants.
Bacterial mutagenicity testing of furans that can be metabolically oxidized
to reactive ,-unsaturated dicarbonyl (2-ene-1,4-dicarbonyl) intermediates is
problematic owing to their high bacterial toxicity. The cytotoxicity of these
substances is believed to arise from their interactions with protein sulfhydryl and
amino groups (Marnett et al., 1985; Eder et al., 1992). Owing to the nature of the
GSH conjugation pathway, genotoxicity studies in which high concentrations of
,-unsaturated carbonyl compounds are formed are likely to create oxidative
stress. It is anticipated that cells exposed to high concentrations of these types of
substances will rapidly deplete GSH levels, eventually leading to cellular damage
and decreased cell viability, as indicated by the above study results.
O-Ethyl S-(2-furylmethyl)thiocarbonate (No. 1526) showed no mutagenic
potential when tested in Escherichia coli WP2uvrA at concentrations of up to 3330
μg/plate, either alone or with a bioactivation system (Verspeek-Rip, 2000).
Evaluated in E. coli PQ37 under the conditions of the SOS chromotest, 3-(2-furyl)acrolein
(No. 1497) tested negative (Eder et al., 1991); however, in a subsequent
evaluation, 3-(2-furyl)acrolein (No. 1497) as well as 2-furyl methyl ketone (No. 1503)
were slightly positive in the SOS chromotest without metabolic activation, as
evidenced by 1.72- and 1.75-fold increases, respectively, in the SOS induction
factor over a background value of 1 (results were considered to be significant if the
induction factor was at least 1.5) (Eder et al., 1993).
In the rec assay, which is based on differential inhibition of growth of
repair-deficient strains as a measure of DNA-damaging activity, Bacillus subtilis
strains H17 (rec+) and M45 (rec) were incubated with 2-methylfuran (No. 1487),