Safety evaluation of certain food additives - ipcs inchem

380 ALKOXY-SUBSTITUTED ALLYLBENZENES
reached 17 adducts/10 6 nucleotides, which is approximately 17–34 times the levels
achieved in the 4-week cola study. No adducts were detected in the livers of mice
administered the non-cola drink or the control groups. During the 8-week study, the
levels of both total DNA adducts and myristicin-derived DNA adducts continued to
increase and reached a maximum of 250 adducts/10 9 nucleotides at 8 weeks;
however, total and myristicin-derived DNA adduct levels were not significantly
different from 4-week levels. In a fourth experiment, two pregnant mice were given
either a single gavage dose of 6 mg of myristicin (300 mg/kg bw) on day 16 or two
doses on days 16 and 17 of gestation. Maternal and fetal liver DNA were isolated
24 h after dosing. Regardless of dosing regimen, myristicin-derived DNA adduct
levels reached approximately 3 times those observed in non-pregnant females. The
level of myristicin-related adducts achieved after animals were maintained on cola
drinks for 8 weeks (~20 adducts/10 8 nucleotides) corresponds to the level achieved
after a single dose of approximately 5–6 mg/kg bw, assuming a linear dose–
response for DNA adduct formation (Randerath et al., 1993).
(b) Human DNA adducts
Safrole-derived DNA adducts have been identified in humans and rodents,
with the latter showing a clear dose–response relationship. Other alkoxy-substituted
allylbenzenes show similar patterns of dose–response for DNA adduct formation in
rodents. Studies of safrole–DNA adducts in humans are connected mainly to studies
of subpopulations that are chronic chewers of betel quid. Chewing of betel quid
occurs mainly in South-east Asia, and the betel quid is often incorporated into a
commercial mixture called gutkha. Chewing of betel quid or gutkha has been
associated with several human cancers (International Agency for Research on
Cancer, 2004). Gutkha, available in tins, is consumed by placing a pinch in the
mouth between the gum and cheek and gently sucking and chewing. The excess
saliva produced by chewing may be swallowed or spit out. The saliva of betel quid
chewers contains the alkaloid arecoline, numerous nitrosamines and safrole, with
the approximate concentration of safrole in the saliva of betel quid chewers being
420 μmol/l (Liu et al., 2000; International Agency for Research on Cancer, 2004).
Although chronic human intake of safrole from chewing betel quid (7.5 kg/year in
Taiwan, China) is significant (Wen et al., 2005), there is no strong correlation
between incidence of betel nut chewing and increased incidence of hepatocellular
neoplasms. Levels of safrole–DNA adducts in the livers of betel quid chewers with
oral and liver cancers are low (2/10 7 nucleotides) (Liu et al., 2000).
An increased risk of oral squamous cell carcinoma and oral submucosal
fibrosis has been associated with the chronic chewing of betel quid. Piper betle
flowers contain ~15 mg safrole/g. Based on 32 P-postlabelling analysis, a high
frequency of safrole-derived DNA adducts occurred in betel quid–associated oral
squamous cell carcinoma (77%, 23/30) and non-cancerous matched tissue (97%,
29/30). These adducts were not present in oral squamous cell carcinoma not
associated with betel quid chewing and their paired non-cancerous matched tissue
(P < 0.001) at the limit of detection (