CITRANAXANTHIN
EXPLANATION
Citranaxanthin is a synthetic compound. Its major present-day use
is as an animal feed additive to impart a yellow colour to chicken fat
and egg yolks. It can be used as colouring matter in the same manner
and for the same purposes as other carotenoids (beta-carotene,
beta-apo-8'-carotenal, beta-apo-8'-carotenoic acid ethyl ester, and
canthaxanthin).
Citranaxanthin has about two-thirds of the vitamin A activity of
beta-carotene in chickens. This is equivalent to 1,100 I.U. of vitamin
A per 1 mg of citranaxanthin.
BIOLOGICAL DATA
Biochemical aspects
Absorption, distribution, and excretion
Twenty female Sprague-Dawley rats weighing about 170 g each
received single i.v. doses of 14C-citranaxanthin dissolved in
polyethylene glycol. Each dose was equivalent to 1 mg/kg b.w. At 1,
24, 72, and 168 hours after administration five of the rats were
sacrificed. The 14C content of the following organs and tissues were
determined: heart, liver, lungs, spleen, eyes, pituitary, brain,
kidneys, pancreas, stomach, duodenum, thymus, periovarian and
perirenal fats, ovaries, skin, hair, adrenals, thyroid, and muscle.
The absolute amounts of radioactivity found in each organ were
particularly high in the liver, lungs, and spleen. The radioactivity
found in these organs ranged from 49% (1 hour) to 15% (168 hours) of
the dose in the liver, 14% (1 hour) to 2.7% (168 hours) of the dose in
the lungs, and 2.2% (1 hour) to 0.85% (168 hours) of the dose in the
spleen.
The doses recovered in other organs after 1 hour were 0.7% in the
heart, 0.1% in the brain, and 0.6% in the kidneys. Muscle and adipose
tissue contained 0.3 and 2.6%, respectively of the dose administered
after 1 hour, thus emphasizing the hydrophobic character of
citranaxanthin. All other organs examined contained levels of
radioactivity less than 0.1% of the dose/g 1 hour after
administration. These levels, which were very low and were associated
with large errors of measurement, decreased even further over the 168
hours after administration. The changes in levels of radioactivity
with time were similar in all organs and tissues, decreasing slowly
overall. A half-life of about 140 hours for this decrease was
estimated by a logarithmic regression method (Morgenthaler, 1979).
Four female Sprague-Dawley rats weighing about 160 g each
received 14C- and 3H-citranaxanthin orally by gastric tube.
Citranaxanthin was administered as an oily suspension in
carboxymethyl-cellulose. In both cases 95-98% of the radioactivity was
recovered in faeces (69-80% (first day); 15-28% (second day); 0.7%
(third day)). After 8 days, 0.2-0.8% of the radioactivity was found in
the liver, 0.2% in the urine, and 0.5% in the carcass
(Morgenthaler, 1978).
The average absorption rate of citranaxanthin in poultry was 50%.
The rest was excreted in the faeces. About two-thirds of the absorbed
amount was metabolized to vitamin A; about 40% was present in blood
and other organs. One-third of the absorbed citranaxanthin was
deposited in the fat of various tissues, in skin, and in egg yolk
(Crina, 1974a,b).
Vitamin A activity of citranaxanthin
One hundred and twelve chickens (one-day old) were fed a diet
free of vitamin A for 3 weeks. Divided groups received doses of 1.2,
2.4, 4.8, 6.0, 12.0, or 24.0 mg citranaxanthin daily over a period of
five days. Liver analyses showed storage of citranaxanthin and vitamin
A derived from citranaxanthin (Tiews, 1968a).
Chicks and quails received 40 ppm citranaxanthin and
beta-carotene over 2 weeks in their diets after a 3-week rearing
period without vitamin A. The vitamin A activity of citranaxanthin in
chickens was higher than that of beta-carotene; in quails it was lower
(Tiews, 1968b).
After a 21-day vitamin A-depletion period, groups of 20 laying
hens were fed diets containing 1.5, 3, 6, or 10 ppm citranaxanthin.
Colouration of egg yolk by citranaxanthin was observed. This effect
was found to be influenced by dose and particle size (Kolk, 1974).
After a vitamin A-depletion period of 3 weeks, groups of 14 or 20
chickens were fed diets containing 8.6, 14, 24, or 40 ppm
citranaxanthin for 2 weeks. The control groups received feed which
contained the same amounts of beta-carotene instead of citranaxanthin.
Determination of the liver vitamin A content showed that the formation
of vitamin A from citranaxanthin depended upon the crystal size. The
relative vitamin A activity was 66 to 94% of the activity compared
with beta-carotene (Kolk, 1974).
The vitamin A activity of citranaxanthin was tested in chicken
liver storage tests (Table 1). From this test and others it can be
concluded that citranaxanthin has about two-thirds of the vitamin A
activity of beta-carotene. This is equivalent to 1,100 I.U. of vitamin
A/mg citranaxanthin (Kolk, 1974).
Toxicological studies
Special study on inhalation
Rats
Twelve animals were exposed to citranaxanthin crystalline/ air
mixture at a concentration of 0.29 mg/liter of air during 8 hours. No
deaths occurred. Toxic symptoms were not evident; only slight mucous
membrane irritation was observed (BASF, 1972a).
Special study on mucous membrane irritation
Rabbits
Fifty mg citranaxanthin crystalline was applied to the eyes of
rabbits. No irritation was seen. After 1 hour the eyes had a red
appearance; after 24 hours and 8 days these symptoms were not
noticeable (BASF, 1972a).
Table 1. Vitamin A activity of citranaxanthin
Dosage Vitamin A Vitamin A Relative vitamin A
(ppm in feed) (I.U./liver) (I.U./mg ingested activity
carotenoid) (ß-carotene = 100%)
ß-Carotene "water soluble"
8.65 900 195 100
14.4 1,803 222 100
24.0 2,596 191 100
Citranaxanthin
8.65 544 118 60
14.4 1,080 124 56
24.0 1,991 144 76
Special study on reproduction
Rats
A 3-generation reproduction study with groups of 20 male and 20
female Sprague-Dawley rats was conducted in which the animals were
administered 1000, 3300, or 10,000 ppm citranaxanthin (8.6% dry
powder, equivalent to 86, 284, and 860 ppm active ingredient). Another
group was administered 9000 ppm dry powder without active ingredient.
A control group remained untreated. Treatment of both males and
females started 7 weeks before breeding and continued during the
mating, pregnancy, and rearing periods. Fertility and reproduction
performance were not influenced in any generations (F0, F1, or
F2) or groups. Mating, pregnancy, litter size, birth weights, and
rearing were within normal limits. The indices of fertility,
pregnancy, viability, and lactation did not differ between control and
treatment groups. Animals of the F2-generation were investigated for
malformations; none were observed. Behaviour, appearance, feed and
water intake, and weight gain were not affected by treatment in any
generations or groups. No macroscopic pathological effects were
observed in parents or their offspring. The final macroscopic
examination of the F2-generation animals after 9 weeks of age
revealed no changes due to treatment. Comparisons of organ weights and
histological examinations showed no differences among groups
(Leuschner et al., 1976a).
Special study on skin irritation
Crystalline citranaxanthin was applied to the skin of rabbits in
a 50% aqueous suspension for 20 hours. A red-brownish colouring was
observed, but inflammation was not detected (BASF, 1972a).
Acute toxicity
Species Route LD501 Reference
(mg/kg b.w.)
Mouse (10) i.p. > 6,400 BASF 1972a
Rat (10) oral > 6,400 BASF 1972a,b
Dog (6) oral > 1,590 Leuschner, 1976c
1 Higher doses could not be administered in these studies for
technical reasons.
Rats
Citranaxanthin was administered in the diet to groups of 13 to 15
male and female Sprague-Dawley rats at dose levels of 10, 20, 50, or
100 mg/kg/day for one month. Growth rates and feed consumption were
not significantly different between the treated and the control groups
during the test period. No toxic symptoms or abnormalities in
urinalysis, biochemical values, blood analysis, wet organ weights, or
histopathological changes were found (Kawase et al., 1972).
Four groups of 20 or 30 male and female Sprague-Dawley rats were
maintained over a period of 91 days on a diet containing 25,000,
50,000, or 100,000 ppm 10% citranaxanthin dry powder (equivalent to
2,500, 5,000, and 10,000 ppm active ingredient). Citranaxanthin was
tolerated without externally recognizable toxic symptoms and without
impairment of feed ingestion or growth over a period of 91 days. A
significant increase in total serum lipids was observed in both males
and females during the treatment period. GPT values were temporarily
increased after 8 weeks, but not after 12 weeks.
The absolute and relative weights of the liver and kidneys showed
a significant increase when compared with those of the control group.
All the increases were reversible in the post-observation period,
except that the increase in kidney weight did not revert completely.
No salient pathological changes were observed in any goups. A few
cases of enlargement of the liver proved after histological
investigation to be hyperaemia, in some cases diffuse and in other
cases patchy. Accumulated changes in the cylinders containing protein
in the distal tubule sections of the kidneys were found in all groups
(Hempel et al., 1973).
Long-term studies
Rats
Groups of 25 male and 25 female Sprague-Dawley rats were fed for
two years with graded levels of 1000, 3300, or 10,000 ppm 8.6%
citranaxanthin dry powder (equivalent to 86, 284, and 860 ppm active
ingredient). Another group was administered 9000 ppm dry powder
without active ingredient. A control group remained untreated. After 6
months the highest concentration of 10,000 ppm was raised to
20,000 ppm (1720 ppm active ingredient) and the concentration of the
placebo was raised to 18,000 ppm for the remaining period of the
experiment.
There were no signs of incompatibility in any groups throughout
the experiment. Appearance, behaviour, weight gain, haematology,
clinical chemistry, urinalysis, weight of organs, and their autopsy
did not reveal any influence of treatment. There were no histological
changes in organs or tissues. The number and kind of tumours or
mortality did not differ among groups (Leuschner et al., 1976b).
Dogs
A 180-day feeding trial with 5 groups of 8 beagle dogs (4 males
and 4 females) was performed with graded levels of 1000, 3300, or
10,000 ppm 8.6% citranaxanthin dry powder (equivalent to 86, 284, and
860 ppm active ingredient). Another group was administered dry powder
without active ingredient. A control group remained untreated. In all
groups with citranaxanthin the faeces had a remarkable red-brown
colour. At the highest level the faeces were more liquid than normal.
Feed intake decreased in a dose-dependent manner due to palatability
problems. The dry powder group without citranaxanthin also had
decreased feed intake.
Appearance, behaviour, weight gain, haematology, clinical
chemistry, electrocardiography, urinalysis, weight of organs, and
their autopsy did not reveal any influence of treatment. There were no
pathological or histological changes in organs or tissues
(Leuschner et al., 1975).
Observations in man
No information available.
COMMENTS AND EVALUATION
The major present-day use of citranaxanthin is as an animal feed
additive to impart a yellow colour to chicken fat and egg yolk. It may
also be used as a colouring agent by adding it directly to food.
If the substance were to be used as a direct food colouring
agent, the data were not sufficiently comprehensive for evaluation
(e.g. only one lifetime feeding study was available). The Committee
concluded that further data of the type outlined in Annex III of
"Principles for the Safety Assessement of Food Additives and
Contaminants in Food" for synthetic food colours are required before
the substance can be fully evaluated for direct food use (Annex 1,
reference 76).
For its use as an animal feed additive, an evaluation could not
be made because the data base did not include sufficient information
on the nature of residues to be found in animal-derived foodstuffs and
because there was no information concerning the use levels that would
constitute good animal husbandry practice.
REFERENCES
BASF (1972a). Ergebnisse der gewerbetoxikologischen Vorprufung.
Unpublished report from BASF Department of Toxicology. Submitted to
WHO by BASF Aktiengesellschaft, Ludwigshafen, FRG.
BASF (1972b). Report on tests for acute oral toxicity of
citranaxanthin dry powder in rats. Unpublished report from BASF
Department of Toxicology. Submitted to WHO by BASF Aktiengesellschaft,
Ludwigshafen, FRG.
Crina (1974a). Citranaxanthin for broilers No. 1. Unpublished report.
Submitted to WHO by BASF Aktiengesellschaft, Ludwigshafen, FRG.
Crina (1974b). Citranaxanthin for broilers No. 2. Unpublished report.
Submitted to WHO by BASF Aktiengesellschaft, Ludwigshafen, FRG.
Hempel, K.J., Zeller, H., Kirsch, P., Koob, K., & Freisberg, K.O.
(1973). Report on the examination of citranaxanthin 10% dry powder in
a 91-day feeding test with rats. Unpublished report from Allgemeines
Krankenhaus, Pathological Institute of Heidberg, Hamburg and BASF,
Department of Toxicology. Submitted to WHO by BASF Aktiengesellschaft,
Ludwigshafen, FRG.
Kawase, S., Komatsu, Y., Suzuki, Y., Nishida, S., & Kobayashi, A.
(1972). Subacute toxicity of citranaxanthin. J. Med. Soc. Toho.,
Japan, 19, 499-504.
Kolk, J.H.H. (1974). About vitamin A efficiency and pigmenting effect
of three citranaxanthin preparations at chicks and quails with
different crystal size. Dissertation, University of Munich.
Leuschner, F., Leuschner, A., Schwerdtfeger, W., & Dontenwill, W.
(1975). Oral toxicity of citranaxanthin, batch BASF No. 10 - called
for short "cn" - and of the substance without agent - called for short
"swa" - in the beagle dog (repeated dosage over 6 months). Unpublished
report from Laboratorium für Pharmakologie und Toxikologie, Hamburg,
to BASF. Submitted to WHO by BASF Aktiengesellschaft,
Ludwigshafen, FRG.
Leuschner, F., Leuscher, F., & Dontenwill, W. (1976a). Oral toxicity
of citranaxanthin-trockenpulver, batch BASF No. 10 - called for short
"cn" - and of the substance without agent, batch 908 E 953 called
"swa" - in the Sprague-Dawley rat (reproduction study covering three
succeeding generations). Unpublished report from Laboratorium fur
Pharmakologie und Toxikologie, Hamburg, to BASF. Submitted to WHO by
BASF Aktiengesellschaft, Ludwigshafen, FRG.
Leuschner, F., Leuschner, A., Schwerdtfeger, W., & Dontenwill, W.
(1976b). Two-year toxicity testing of citranaxanthin dry powder, batch
BASF No. 10 - called for short "cn" - and of the substance without
agent, batch 908 E 953 called "swa" - in the Sprague-Dawley rat.
Unpublished report from Laboratorium fur Pharmakologie und
Toxikologie, Hamburg, to BASF. Submitted to WHO by BASF
Aktiengesellschaft, Ludwigshafen, FRG.
Leuschner, F. (1976c). Prufung der akuten Toxizität yon
citranaxanthin. Charge BASF NR. 10- kurz "CN" genannt- an
mischrasaigen Hunden bei peroraler Verabreichung. Unpublished report
from Laboratorium fur Pharmakologie und Toxikologie, Hamburg, to BASF.
Submitted to WHO by BASF Aktiengesellschaft, Ludwigshafen, FRG.
Morgenthaler, H. (1978). Citranaxanthin balance and excretion study.
Unpublished report from BASF Pharma Division. Submitted to WHO by BASF
Aktiengesellschaft, Ludwigshafen, FRG.
Morgenthaler, H. (1979). Organ citranaxanthin - distribution.
Unpublished report from BASF Pharma Division. Submitted to WHO by BASF
Aktiengesellschaft, Ludwigshafen, FRG.
Tiews, J. (1968a). Certified report about vitamin A activity of
citranaxanthin and other carotenoids. Unpublished report. Submitted to
WHO by BASF Aktiengesellschaft, Ludwigshafen, FRG.
Tiews, J. (1968b). Citranaxanthin for egg yolk pigmentation.
Proceedings from Lohmann Nutrition Conference, Cuxhaven, pp. 47-50.
See Also:
Toxicological Abbreviations
CITRANAXANTHIN (JECFA Evaluation)