Safety evaluation of certain food additives - ipcs inchem

366 ALKOXY-SUBSTITUTED ALLYLBENZENES
epoxidation and hydrolysis metabolites were detected in the urine. As expected,
3,4-dihydroxy-5-methoxyallylbenzene, the product of O-demethylenation of
myristicin, was the major metabolite. However, no 1-hydroxylation metabolites
could be detected by this GC/electron impact MS method. The presence of the
1-hydroxy metabolites in rats given the pure substances at 100 mg/kg bw and
their absence in rats given nutmeg at 500 mg/kg bw may be due to higher dose
(100 versus 1–2 mg/kg bw) or to an effect of the rats being administered a nutmeg
matrix, which alters the metabolic fate of each of these alkoxy-substituted
allylbenzenes (Beyer et al., 2006).
In a human who reported ingesting the powder of about five nutmegs
(20–50 g of nutmeg, corresponding to 140–280 mg elemicin or 2.3–4.6 mg elemicin/
kg bw, 100–200 mg myristicin or 1.6–3.2 mg myristicin/kg bw, and approximately
20 mg safrole or 0.3 mg safrole/kg bw), analysis of the urine revealed that the major
metabolites of each of the three constituents were detected. As for rats given ground
nutmeg, no 1-hydroxylation metabolite was detected. For both rats and humans
exposed to nutmeg, the corresponding O-demethylenation metabolite of safrole or
myristicin was the predominant metabolite, exceeding other metabolites by at least
a factor of 10. The side-chain demethylation products were the major metabolites
of elemicin (Beyer et al., 2006).
Two humans were administered an oral dose of 1.66 mg of [1- 14 C]safrole,
and urine was collected for 24 h. The percentage of radioactivity extracted from
urine increased from 32% to 73% after treatment with glucuronidase, indicating that
a majority of urinary metabolites were glucuronic acid conjugates. Analysis of urine
metabolites by GC/MS indicated that the O-demethylenation product was the major
metabolite (65%). At the limits of detection (approximately 10 times less than the
measured level of O-demethylenation metabolite), no 1-hydroxy metabolite could
be detected (Benedetti et al., 1977). In the same study, rats were administered
[1- 14 C]safrole at single oral doses of 0.90, 60 or 600 mg/kg bw, and urine was
collected over 48 h. Glucuronidase hydrolysis significantly increased the
percentage of radioactivity that was extracted, indicating that glucuronic acid
conjugates accounted for the majority of urinary metabolites. The major metabolite
was 1,2-dihydroxyallylbenzene, but its proportion decreased significantly when the
dose was increased from 60 to 600 mg/kg bw. At 600 mg/kg bw, 1-hydroxysafrole
was detected in the urine. The other metabolites identified were 3-hydroxyisosafrole
and 3(4)-hydroxy-4(3)-methoxyallylbenzene. Other studies using relatively high
dose levels of either safrole or myristicin via the oral or intraperitoneal route support
the observation that 1,2-dihydroxyallylbenzene is the major metabolite. The
detection of the 1-hydroxy metabolite in rats correlates with the appearance of low
levels of protein and DNA adducts in rodents (see below).
Safrole was largely metabolized by O-demethylenation in male Swiss-
Webster mice, Sprague-Dawley rats or hamsters. When each of these species was
administered [methylenedioxy- 14 C]safrole, 1,2-dihydroxyallylbenzene was
produced as the major metabolite, resulting from oxidative metabolism that
produces [ 14 C]formate or [ 14 C]carbon dioxide, which were both identified (Kamienski
& Casida, 1970).