TRIETHYL CITRATE
Explanation
The citrate ion is widely distributed in plant and animal tissues
and is a naturally occurring component of man's diet. It is a common
metabolic intermediate in oxidative metabolism. Citrate was evaluated
by the ninth session of the JECFA and was given an ADI not limited.
BIOLOGICAL DATA
BIOCHEMICAL ASPECTS
Triethyl citrate is an odourless, nearly colourless, oily liquid.
No absorption or metabolism studies have been reported, however, it is
expected that the compound would rapidly metabolize in the body and
liberate the citrate ion which would be handled through the usual
biochemical pathways (FASEB, 1976).
TOXICOLOGICAL STUDIES
Acute toxicity
LD50
Species Route (mg/kg bw) Reference
Rat p.o. 8 000 Finkelstein & Gold, 1955
Cat p.o. 4 000 Finkelstein & Gold, 1955
Short-term studies
Mouse
A group of 20 mice given intraperitoneal doses of 350 mg/kg bw of
triethyl citrate daily for 14 days had a slightly lower mean growth
rate than control animals. No differences were seen in the two groups
in erythrocyte and leucocyte blood cell count, clotting time and
haemoglobin levels. Examination of the liver, lung and kidney tissues
of two animals at necropsy revealed no pathological cellular changes.
Rat
Young rats were fed triethyl citrate at an initial rate of 1, 2
and 4 g/kg bw for eight weeks (Finkelstein & Gold, 1955). Urinalysis,
blood counts and growth measurement, performed periodically, revealed
no toxic effects. At necropsy, no gross abnormalities were seen in the
thoracic or abdominal organs. Histological sections of the heart,
lungs, gastrointestinal tract, liver, pancreas, spleen and kidneys
were comparable in appearance to those from the untreated controls.
Cat
Cats receiving daily doses of 7% of the LD50 (280 mg/kg bw) for
eight weeks did not differ from control animals with respect to
weight, blood count, haemoglobin, blood sugar and blood nitrogen.
However, weakness, ataxia and depression appeared after the fourth or
fifth dose and progressed. After treatment was discontinued, the
animals recovered within 24-96 days (Finkelstein & Gold, 1959).
Dog
Two young adult male and two young adult female beagle dogs were
given daily doses of triethyl citrate of 0.05 and 0.25 ml/kg bw for
six months. Measurement of body and organ weights, blood and
urinalysis and the results of histological examination of tissues
revealed no adverse effects (Hodge, 1954). Increasing the daily dose
to 2.5 to 3.5 ml/kg bw for seven to 12 weeks resulted in liver
pathology in three treated animals. A fourth dog that had previously
reacted adversely to a 2 ml/kg bw dose showed no histological changes
after receiving 1.5 ml/kg bw daily for an additional month.
Long-term studies
Rat
Three groups of 15 male and 15 female weanling Sprague-Dawley
rats were fed diets containing 0.33, 1.0 and 3.0% triethyl citrate in
a two-year feeding study (LaWall & Harrison, 1954). The initial doses
were from 0.2 to 2.0 g/kg bw. Weight gain and food intake were reduced
below that of the control groups when the level of the compound in the
diet was increased. (No specific numbers were given for these
results.) No adverse effects of haematologic, urinalysis, survival,
gross or histopathologic parameters could be attributed to triethyl
citrate.
Special studies on reproduction and teratology
At doses ranging from 0.5 to 10 mg/kg b.w. triethyl citrate was
nonteratogenic in the chicken embryo. When injected into the air cell,
the LD50 was 1349.86 mg/kg bw (67.49 mg/egg) (Verrett, 1976).
Special studies on mutagenesis
Triethyl citrate was not mutagenic in plate and suspension tests
using the Ames Salmonella microsome mutagenesis assay in strains TA
1535, TA 1537 and TA 1538 and the Saccharomyces cerevesiae D4 yeast
assay with and without tissue homogenate activating systems (Litton
Bionetics, Inc., 1976).
Special studies on neurological activity
Rat
In Wistar rats dose intraperitoneally at 400 mg/kg bw triethyl
citrate produced a loss of the righting reflex, an effect reversible
within 15 minutes.
Rabbit
Intravenous administration of a 100 mg/kg bw dose of triethyl
citrate to rabbits produced a marked increase in motor activity and
respiration (Meyer et al., 1964).
Comments
Citrate was evaluated by the ninth session of JEFCA (1966)1 and
ADI not limited was given. It is likely that triethyl citrate will be
hydrolyzed to its component parts, citrate and ethanol in vivo. Data
from two-year feeding studies suggest that rats can tolerate up to
2.0 g/kg. Dogs tolerated up to 0.25 ml/kg bw for six months without
effects.
Triethyl citrate was not mutagenic in several microbiological
assays.
EVALUATION
Level causing no toxicological effect
Rat: 2 g/kg bw
Estimate of temporary acceptable daily intake for man
0-10 mg/kg bw
FURTHER WORK OR INFORMATION
Required by 1981.
Repeat metabolic studies in several species, preferably including
man.
1 Changed to 1973 on draft which was seventeenth session.
REFERENCES
FASEB (1976) SCOGS, 84, Contract No. FDA 223-75-2006, submitted to
FDA, Washington, D.C.
Finkelstein, M. & Gold, H. (1959) Tox. Appl. Pharmacol., 1, 283
Hodge, H. C. (1954) Unpublished data submitted to FASEB
LaWall, (?) & Harrison, (?) (1954) Unpublished, prepared for
Fleishmann Laboratories, Standard Brands, Inc., Stamford, Conn.,
USA
Litton Bionetics, Inc. (1976) FDA-75-10 LBI Project No. 2468,
unpublished data submitted to the FDA
Meyer, D., Aulian, J. & Guess, W. L. (1964) J. Pharm. Sci., 53, 776
Smith, H. et al. (1976) Health Physics, 30, 318
Verret, M. J. (1976) Unpublished data, Food and Drug Administration