SORBITAN MONOESTERS OF PALMITIC, STEARIC, OLEIC AND LAURIC
ACIDS AND TRIESTERS OF STEARIC ACID
Explanation
Sorbitan monoesters of palmitic and stearic acids and triesters
of stearic acid have been evaluated for acceptable daily intake by the
Joint FAO/WHO Expert Committee on Food Additives in 1974 (see Annex I,
Ref. 32) and a toxicological monograph was prepared (see Annex I, Ref.
33). Sorbitan monoesters of oleic and lauric acids have not previously
been evaluated by JECFA. The previous published monograph has been
expanded to include sorbitan esters of oleic and lauric acids.
BIOLOGICAL DATA
BIOCHEMICAL ASPECTS
The fatty acid moiety of sorbitan monostearate has a coefficient
of digestibility of 53.3% (Oser & Oser, 1957b).
Experiments with 14C-labelled sorbitan monostearate showed that
at least 90% of the emulsifier, when fed to rats in oily solution, was
hydrolysed to stearic acid and anhydrides of sorbitol. A significant
fraction of the administered 14C was expired as CO2. When the
labelled material was administered in water, 16-25% was recovered in
the urine; when it was given in oil, 44-66% was recovered. Of the
ingested radioactivity, 3-7% was recovered in the tissues 48 hours
after feeding. Fractionation of the carcass fats showed that 14C was
incorporated into fatty acids, glycerol and a residue that did not
sublime (Wick & Joseph, 1953).
Sorbitan trioleate prepared with a 14C-label in the sorbitol
or the oleate moieties was administered orally to rats. After
administration of sorbitan 14C-trioleate, the appearance of 14C-CO2
in the expired air reached a peak at about 6 hours and amounted to
30-35% of administered label. The faeces and gastrointestinal tract
contained about 42% of the 14C-label, indicating that it was
incompletely absorbed, and 3% appeared in the urine; the liver
contained about 3% and the carcass about 22%. After administration of
the 14C-sorbitan-labelled ester, less than 2% of the label was
recovered as 14C-CO2; the proportions not absorbed were 24% from a
water emulsion and 37% from a solution in oil; the proportions
recovered of that absorbed were as follows: urine, 88%; expired air,
5%; liver, 1%; carcass, 6% (Treon et al., 1967).
TOXICOLOGICAL STUDIES
Acute toxicity
The physical properties and low toxicity of the partial esters of
sorbitan are such that formal acute toxicity tests are for the most
part impracticable.
Acute feeding tests on sorbitan monopalmitate have been conducted
in the rat. No toxic symptoms were observed in 10 male rats, weighing
100-175 g, using the ester as their sole ad libitum diet (except for
water) for 24 hours, during which they consumed an average of 1.5 g
per animal or approximately 10 g/kg bw (Krantz, 1947c).
For 10 rats, sorbitan monostearate was mixed with a diet at a
concentration of 50%. These animals weighed 175-250 g and, within 10
hours, had ingested about 3 g of the ester. They all appeared unharmed
after 3 days.
No toxic symptoms were observed in any of 10 female rats,
weighing 125-175 g, fed 10 ml/kg bw of sorbitan tristearate by stomach
tube, in the form of a 50% aqueous emulsion, and observed over a 6-day
period. Four of the 10 animals, all of which appeared normal, were
sacrificed and gave normal histological findings in the livers and
kidneys. In 10 female rats, weighing 125-175 g, intraperitoneal
injection of sorbitan tristearate in doses of 10 ml/kg (50% aqueous
emulsion form) produced 2 fatalities in 48 hours of observation; the
other animals appeared normal (Krantz, 1947d).
Sorbitan monopalmitate ("Span 40"), sorbitan monostearate ("Span
60") and sorbitan tristearate ("Span 65"), in the maximal orally
administerable doses (15.9 g/kg), produced no mortality in rats
(Brandner, 1973).
The LD50 of orally administered sorbitan (monooleate) and
sorbitan monolaurate in the rat was 39.8 and 37.5 g/kg, respectively
(Quigley, 1966). Diarrhoea occurred in all rats given either sorbitan
monooleate or laurate. Autopsy of the surviving animals 14 days after
treatment showed a high incidence of hydronephrosis.
Short-term studies
Hamster
Hamsters averaging 46 g in weight were segregated by sex into
groups varying in size from 14 to 22 and fed diets containing sorbitan
monolaurate at levels of 0, 5 and 15% for 68 days. Treated animals
developed mild diarrhoea and a depressed growth rate. The high-dose
group suffered 22% mortality compared to 8% in the control group.
Treatment-related effects were noted in the gastrointestinal tract,
including mucosal and intramural hyperaemia and oedema, with mild
infiltration by inflammatory cells. In the kidney of treated animals,
the cortical tubular epithelium exhibited fraying at the free edges of
cells, eosinophilic granularity and nuclear pyknosis. The kidney
alterations were regarded as reversible. Incomplete maturation in
testes and ovaries was more frequent in treated animals (Harris,
1951b).
Rat
Groups of 10 young rats were fed for 6 weeks diets containing 1%
or 4% of sorbitan monostearate. There was no effect on weight gain,
nor were there any significant changes histopathologically in the
liver, kidneys, intestine and bladder (Krantz, 1946).
Sodium monostearate was added to diets designed to induce hepatic
necrosis in rats. Levels up to 10% tended to prolong the survival time
and had no significant effect upon the hepatic changes over periods up
to 120 days (Gyorgy et al., 1958).
Rats in groups of 5 receiving sorbitan monostearate in their diet
for 6 weeks at levels of 5% or 15% showed no change in bile duct size
(Krantz, 1951).
Groups each of 30 Wistar rats (initial body weight 84-87 g)
equally divided by sex were fed sorbitan monolaurate at dietary levels
of 0, 2.5, 5.0 and 10%. Haematological and urinary analyses were
carried out at weeks 2, 6 and 13 and serum clinical chemistry at weeks
6 and 13. At weeks 2 and 6, 5 male and 5 female animals from each
group were sacrificed, and at the end of the thirteenth week all
surviving animals were sacrificed. Animals fed 5% and 10% test diet
showed statistically significant dose-related decreases in haemoglobin
levels, packed cell volumes (2, 6, 13 weeks) and total leucocyte count
(13 weeks, males only). No treatment-related effects were observed in
clinical chemistry values or urinalyses. At autopsy, organ weights
were determined, and a biological examination made of the brain,
pituitary, thyroid, heart, liver, spleen, kidneys, adrenal glands,
gonads, stomach, small intestine, caecum, lung, salivary gland, aortic
arch, thymus, various lymph glands, urinary bladder, colon, rectum,
pancreas, uterus and skeletal muscle. An increase in relative liver
weight occurred in the high-dose animals, and increased relative
kidney weight occurred in all test groups. These effects were first
observed in animals maintained on test diets for 2 weeks. No adverse
histological findings could be demonstrated in the kidney or other
tissues, except in the livers of animals in the high-dose groups where
there was an increased incidence of periportal vacuolation (Cater et
al., 1978).
Groups of 10 male and 10 female Osborne-Mendel rats, initial
weight 40-50 g, were fed diets containing 0, 15, 20 or 25% sorbitan
monolaurate for 23 weeks. Treated animals exhibited diarrhoea, an
unkempt appearance and severe growth retardation. At the 25% dose
level, only one animal of each sex survived the study. Upon gross
pathological examination, the livers of treated animals showed
paleness and enlargement, with a marked enlargement of the common bile
duct. Histological studies of the tissues showed marked liver damage
at all dose levels which consisted of fatty changes and fibrosis.
There was no bile duct proliferation but there was great common bile
duct enlargement. Focal nephritis was observed in the kidney and there
was a marked increase in the incidence of foamy alveolar macrophages
in the lungs of treated animals. No other tissues exhibited treatment-
related effects (Fitzhugh et al., 1960).
Weanling male Sprague-Dawley rats were distributed into groups of
14 and fed sorbitan monolaurate for 59 days at dietary levels of 0 and
25%. Treatment-related symptoms included reduced rate of growth,
reduced food consumption, diarrhoea, nasal haemorrhage and gangrenous
tails. Only 1 rat survived the treatment regimen, presenting a stunted
appearance resembling starvation (Harris et al., 1951a). In another
study, 14 male and 16 female rats were fed sorbitan monolaurate in
doses increasing to 25% by day 10 of the study, and continuing at that
level for 60 additional days. The toxic effects were similar to those
reported in the previous study. Results from pair-fed controls
indicate that the reduction in growth was not caused primarily by
reduced food consumption. Haematology at termination of the study
showed a treatment-related decrease in haemoglobin value. At autopsy,
increased relative organ-to-body weight was observed for brain,
kidney, heart, spleen, lung and liver. Histological studies of tissues
showed mild degenerative lesions in the kidney, necrosis of the liver,
and incomplete maturation of testes. No other effects were reported
(Harris et al., 1951a).
Groups of 6 female Holtzman rats, 21-24 days old, were fed diets
containing 0, 15 and 20% of sorbitan monolaurate for 21 days. All
animals on test diets suffered diarrhoea, alopecia, unthrifty
appearance, reduced rate of growth and increased mortality. No
pathological evaluation was made (Ershoff, 1960).
White male rats of unspecified strain, initial weight 60 g, were
distributed into groups of 4 or 5 and fed diets containing 0, 1 and 4%
sorbitan monolaurate for 6 weeks. A significant reduction in growth
rate occurred in the high-dose group. No significant histopathological
changes were reported in liver, intestine or bladder, but coagulated
fluid was present in the renal tubules (Krantz, 1946).
Wistar rats, initial weight 89-94 g, were distributed into groups
of 15 males and 15 females and fed sorbitan monooleate at dietary
levels of 0, 2.5, 5.0 and 10% for 16 weeks. Animals on test diets
showed a decreased weight gain that was related to a reduction in food
intake. At weeks 2, 6 and 16, haematology, serum clinical chemistry
and urinalysis were carried out. Haematology studies showed lower
values for haemoglobin and packed cell volume in female rats fed 10%
sorbitan monooleate, with a significantly lower mean erythrocyte
count. Variations in clinical chemistry values did not appear to be
compound related. No compound-related effects were observed in the
urinalysis.
Autopsy of the test animals at the termination of the study
showed kidney enlargement in females in the 5% and 10% test groups.
Histological studies showed renal damage in these groups, as well as
periportal fatty changes in the liver of female rats in the 10% group.
No other compound-related histopathology was reported (Ingram et al.,
1978).
Groups of 10 male white rats of unspecified strain, initial
weight 100 g, were fed sorbitan monooleate at dietary levels of 0 and
10% for 6 weeks. Reductions in food consumption and in rate of growth,
and mild diarrhoea occurred in treated animals. Histological sections
from liver and kidney showed no differences between control and
treated animals. Haematological and serum clinical chemistry were
carried out at weeks 3 and 6 of the study. There were no significant
differences between test and control animals. At autopsy (3 weeks and
6 weeks), gross pathological and histological studies of selected
organs (liver and kidney) from 3 rats showed no compound-related
effects (Krantz, 1953).
Dog
Dogs were fed sorbitan monostearate in a semi-synthetic diet at a
level of 5% for 19-20 months. There was no appreciable difference in
food intake, weight, maintenance and longevity between controls and
those fed sorbitan monostearate. The microscopic examination of the
tissues showed no changes attributable to the feeding of sorbitan
monostearate, with the exception of some haemosiderosis of the liver
(Fitzhugh et al., 1959).
Monkey
Two rhesus monkeys, fed daily with 0.7-0.8 g/kg bw of sorbitan
monostearate for 5 weeks, appeared unharmed throughout. No damage to
the liver and kidneys was seen post mortem (Krantz, 1946).
Two Macacus rhesus monkeys of unspecified sex (initial weights
2.25 and 2.85 kg) were fed 2 cc of sorbitan monolaurate per day in
their diet for 6 weeks. Because no control animals were used in the
study, the haematology and growth results are difficult to interpret.
Histological sections from liver and spleen were reported to be normal
in appearance. However, some kidney damage was evident, including
shrinking and slight serous exudation into some of the glomerular
spaces, swelling of the lining epithelium of the convoluted tubules,
and fragmentation and debris in the lumina of some tubules. Because of
the absence of tissue sections from control animals, the apparent
kidney damage cannot be unequivocally ascribed to treatment (Krantz,
1946).
Long-term studies
Rat
A life-span (2-year) study in 30 male rats given 5% sorbitan
monopalmitate in their daily diet showed no alteration in the growth
pattern or survival of the test rats, as compared with controls, and
no abnormalities that could be attributed to the experimental diet.
Blood studies and histopathological studies of the principal viscera
were made during and at the end of the experiment. Examination of the
brain, spleen, pancreas, adrenal gland, bladder, bone marrow, heart,
lymph nodes, lung, testicle and muscle, revealed nothing of a
pathological nature attributable to the experimental diet (Krantz,
1947a).
Thirty rats were fed on a diet containing 5% sorbitan
monostearate for up to 2 years. Growth rate and survival were similar
to those of the controls. There were no histological abnormalities
post mortem that could be attributed to the diet (Krantz, 1947a).
Experiments were conducted over a period of 2 years on 4
generations of rats (30 rats in each group). At levels of 5% and 10%
in the diet, no effects were observed on growth, food efficiency,
reproduction, lactation, metabolism, behaviour, mortality, or the
growth and histopathological appearance of the tissues. At a level of
20%, retardation of growth and impairment in lactation were noted, but
mortality was not increased. The weight of the liver and kidneys was
increased, but both appeared to be histologically normal (Oser & Oser,
1956a,b, 1957a,b).
Sorbitan monostearate was fed to groups of 24 rats at levels of
2, 5, 10 and 25% in the diet for 2 years. Levels of 2% and 5% did not
produce evidence of toxicity. The substance caused a significant
increase in mortality at the 10% and 25% levels, with growth
depression and enlargement of the liver and kidneys (Fitzhugh et al.,
1959).
A life-span (2-year) chronic feeding study was conducted on 30
male rats, using 5% sorbitan tristearate in their diet. From this
experiment it was concluded that there was no alteration in the growth
pattern or survival of the test rats as compared to the controls, nor
were there any abnormalities that could be attributed to the
experimental diet (Krantz, 1947e).
A life-span (2-year) study was conducted with 30 white male rats
(strain unspecified, initial weights 54-63 g) that were given 5%
sorbitan monolaurate in their daily diet. No effect on growth or
mortality of the test rats, as compared with controls, could be
attributed to the test compound. Blood chemistry, haematology,
histopathological examinations and gross pathological examinations
of liver, kidney, spleen, brain, adrenals, urinary bladder,
gastrointestinal tract, pancreas, thyroid, heart, lung, testicle,
salivary gland, prostate, parathyroid, pituitary, striated muscle and
bone marrow were carried out both during the study, following interim
sacrifice at 6, 12 and 17 months, and at termination of the study. No
treatment-related changes were reported (Krantz, 1950a).
Groups of 10 male and 10 female weanling Sprague-Dawley rats were
fed diets containing 0, 5 and 10% sorbitan monolaurate for 2 years.
Animals consuming a 10% sorbitan monolaurate diet suffered diarrhoea
and a statistically significant reduction in growth, but animals fed
the 5% diet showed no adverse treatment-related effect. Because food
consumption data were inadequate, it could not be ascertained whether
the reduced growth was caused by reduced food consumption or by a
direct toxic effect. Liver, kidney, heart, aorta, spleen, pancreas and
body fat exhibited no treatment-related abnormalities when examined
grossly and histologically.
A group of 30 white male rats (strain unspecified, initial weight
54-63 g) were maintained on a diet containing 5% sorbitan monooleate
for a period of 2 years. There was a minor retardation of growth, and
no effect on mortality. Haematology and serum clinical chemistry tests
were carried out at months 6, 12 and 17 of the study. No compound-
related effects were reported. At months 6, 12 and 17, 1 control
and 1 test animal were sacrificed for histopathological examination of
liver, kidney and bone marrow, and at week 104, all surviving animals
were sacrificed. At autopsy, gross pathological and histopathological
examination of brain, spleen, pancreas, thyroid, parathyroid,
prostate, pituitary gland, salivary gland, adrenal, bladder, bone
marrow, heart, lymph node, lung, testicle and muscle did not show any
compound-related effects (Krantz, 1950b).
OBSERVATIONS IN MAN
Sorbitan monostearate given to 9 human subjects in doses of
6 g/day for 28 days had no significant effect on the gastric activity
or on the activity of the gastrointestinal tract (Steigmann et al.,
1953).
Other experiments on 16 human subjects With the same doses and
for the same period showed no deleterious effect. Blood chemistry
(including cholesterol), other haematological findings, urine analyses
and liver function tests were normal (Waldstein et al., 1954).
In another study 4 g of sorbitan monostearate were fed daily to 2
children for 32-37 days without harmful effects (Preston et al.,
1953).
Comments
Metabolic studies indicate that a significant portion of the
sorbitan esters are hydrolysed to the fatty acid moiety and anhydrides
of sorbitol.
The partial esters of sorbitan have been investigated in both
short-term and long-term experiments. Some have also been studied in
man.
Some changes in liver and kidney have been reported in recent
short-term studies with sodium monolaurate and sodium monooleate at
dietary levels of 10%. The most significant changes occurred in the
liver of rats fed sodium monolaurate, the changes being primarily
fatty changes, intralobular fibrosis, and enlargement of the common
bile duct; no bile duct proliferation was reported. The esters also
caused some kidney enlargement, but there were no histological
changes. The changes reported appeared to be related to the fatty acid
moiety of the ester.
Long-term feeding studies in the rat are available for all the
esters considered in this monograph. Although these are older studies,
the available information shows that no compound-related effects were
observed when the esters were fed at 5% of the diet.
From the toxicological point of view, the evidence provides a
basis for evaluating the sorbitan esters as a group.
EVALUATION
Level causing no toxicological effect
Rat: 50 000 ppm (5%) in the diet equivalent to 2500 mg/kg bw.
Estimate of acceptable daily intake for man
0-25 mg/kg bw.*
* Group ADI. As the sum of the sorbitan esters of lauric, oleic,
palmitic and stearic acid.
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