Absorption, Distribution and Excretion
Following oral administration of the dye to rats, 3% of the dye was absorbed and excreted unchanged in urine and bile; therefore, the reduction in dye in the liver was minimal. … Following intravenous injection in rats, 20-30% of the dye was excreted in bile. … Within 24 hours of administration, trace amounts up to 1.5% of the unchanged monomeric dye were excreted in urine and bile. No unchanged dye was absorbed after administration of the polymer derivative. In animals given Sunset Yellow and its polymer derivatives, the absorption rates of the azo bond cleavage product 1-amino-2-naphthol-6-sulfonic acid were 8.5% and 6.9%, respectively, while the absorption rates of the cleavage product sulfamate were 37.4% and 0%, respectively. … In five animals, after administration of 14C-Sunset Yellow (2.7 mg, 4.62 μCi) for 96 hours, the amount of radioactive material excreted in urine was 8.5 ± 3.4% of the dose. Sunset Yellow rats contained 40 molar equivalents of sulfamate in their 24-hour urine. The intact dye content in urine after 24 hours was 1-2% of the dose. Peak fecal excretion occurred in the first 24 hours. The recovery rate of radioactive material was 94.5 ± 5.7%. The total radioactive recovery rate was 103 ± 3.3%.
In 14 rats, after oral administration of 2-25 mg of Sunset Yellow, 0.3% and 1.5% of the administered dye were excreted in urine and bile, respectively, within 72 hours. 37% of the sulfamethoxam equivalent was excreted in urine.
Metabolism/Metabolites

After oral administration of the dye to rats…unabsorbed dye was mainly reduced by intestinal bacteria and excreted in urine as sulfamethoxam and 1-amino-2-hydroxy-6-naphthalenesulfonic acid. …After oral administration, the metabolite in rabbits was acetylsulamine…
Sunset Yellow FCF is readily reduced in vitro by bacteria in the rat intestine and cecum. It can bind to serum proteins. This study investigated the anaerobic reduction of four sulfonated azo dyes (amaranth, sunset yellow, neocarmine, and tartrazine) at a concentration of 50 μM in phosphate buffer (pH 4, with nitrogen as the gas phase) using bacterial suspensions isolated from human feces and rat intestinal contents. Fecal microbiota from five male volunteers reduced these four dyes at average rates of 38.4, 25.1, 18.2, and 6.5 nmol/mg protein/hour, respectively. Despite significant individual differences in age, diet, and living environment, the reduction rates of each dye by the bacterial suspensions varied little among individuals. …The reduction rates of amaranth and sunset yellow by rat intestinal microbiota were 4–5 times higher than those by human fecal microbiota, but there was no significant difference in the reduction rates of neocarmine and tartrazine between the two bacterial suspensions. ...
When rabbits were fed 0.5 g/kg body weight of dye, the following metabolites were detected in their urine after 48 hours: Sunset Yellow (2%), sulfanilic acid (54%), acetaminophensulfonic acid (23%), and 1-amino-2-naphthol-6-sulfonic acid (55% within 24 hours). ...The metabolites in the urine mainly originated from the reduction and cleavage of azo bonds. The liver enzymes that reduce azo bonds play a negligible role in metabolism. Therefore, the reduction of the dye by intestinal bacteria is the most likely pathway to the formation of aromatic amines and aminosulfonic acids; these substances are subsequently partially absorbed by the intestines.
6-hydroxy-5-(phenylazo)-2-naphthalenesulfonate sodium (SS-AN)—an auxiliary pigment in Food Yellow 5 [Sunset Yellow FCF, disodium salt of 6-hydroxy-5-(4-sulfophenylazo)-2-naphthalenesulfonate]—was administered orally to Sprague-Dawley rats. Colored metabolite A, metabolite B, and unchanged SS-AN were detected in the rat urine. Chemical structure analysis revealed that metabolite A (main peak) was 6-hydroxy-5-(4-sulfonoxyphenylazo)-2-naphthalenesulfonic acid, a sulfate conjugate of SS-AN; metabolite B (secondary peak) was 6-hydroxy-5-(4-hydroxyphenylazo)-2-naphthalenesulfonic acid (SS-PAP), a derivative of metabolite A, which did not contain a sulfate group. …After oral administration of SS-AN, it was metabolized in 24-hour urine samples to colorless metabolites (45.3% p-aminophenol, 9.4% o-aminophenol, and 0.4% aniline). Analysis of colored metabolites showed that metabolite A (0.29%), SS-PAP (0.01%), and SS-AN (0.02%) were detected in 24-hour urine samples. Approximately 56% of SS-AN is excreted in urine, with the remainder likely excreted in feces.

Non-Human Toxicity Values
Intraperitoneal LD50 in mice (female): 4600 mg/kg body weight Intraperitoneal LD50 in mice (male): 5500 mg/kg body weight Intraperitoneal LD50 in rats: 3800 mg/kg body weight Oral LD50 in mice: > 6000 mg/kg body weight For more complete non-human toxicity data on CI Food Yellow 3 (out of 8), please visit the HSDB record page.

[1]. Electro-Fenton oxidation of Sunset Yellow FCF azo-dye in aqueous solutions. Desalination, 2011, 274(1-3): 22-30.

[2]. Sunset yellow FCF, a permitted food dye, alters functional responses of splenocytes at non-cytotoxic dose. Toxicol Lett. 2013 Mar 13;217(3):197-204.

[3]. The modifying effect of selenium and vitamins A, C, and E on the genotoxicity induced by sunset yellow in male mice. Mutat Res. 2012 May 15;744(2):145-53.

FD&C Yellow 6 is an orange-red crystal or red powder. (NTP, 1992)
Sunset Yellow FCF is an organic molecular entity.

C16H10N2NA2O7S2

452.3693

451.972

2783-94-0

17730

Pink to red solid powder

390°C (dec.)

4.93

1

9

2

29

722

0

OIQPTROHQCGFEF-UHFFFAOYSA-L

InChI=1S/C16H12N2O7S2.2Na/c19-15-8-1-10-9-13(27(23,24)25)6-7-14(10)16(15)18-17-11-2-4-12(5-3-11)26(20,21)22;;/h1-9,19H,(H,20,21,22)(H,23,24,25);;/q;2*+1/p-2

disodium;6-hydroxy-5-[(4-sulfonatophenyl)diazenyl]naphthalene-2-sulfonate

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Note: Please store this product in a sealed and protected environment (e.g. under nitrogen), avoid exposure to moisture and light.

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

H2O : ~100 mg/mL (~221.06 mM)

Solubility in Formulation 1: 50 mg/mL (110.53 mM) in PBS (add these co-solvents sequentially from left to right, and one by one), clear solution; with sonication.

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 (Please use freshly prepared in vivo formulations for optimal results.)