Absorption, Distribution and Excretion
Following oral administration of FD&C Red 2, 10% appeared in the urine and 43% in the feces (53%). Some absorbed reduction products were further metabolized into unknown products. Four rats were administered a single 50 mg dose orally. Only 2.8% of the drug was absorbed from the gastrointestinal tract; the metabolites in urine and bile were mainly products of azo bond reduction cleavage, such as 1-amino-4-naphthalenesulfonic acid and 1-amino-2-hydroxy-3,6-naphthalenedisulfonic acid. The former compound was also found in feces. The absorption and elimination of 1-amino-4-naphthalenesulfonic acid, one of the azo reduction products, in rats were investigated via gavage, drinking water, and feed mixing. The mammalian hepatic azo reductase system has little effect on its metabolism; almost all reduction reactions occur through the gut microbiota. 1-amino-2-hydroxy-3,6-naphthalenesulfonic acid was not studied due to its poor absorption.
1-Amino-4-naphthalenesulfonic acid is one of the metabolites of amaranth, with an oral absorption rate of 18%.
For more complete data on the absorption, distribution, and excretion of amaranth (12 species), please visit the HSDB record page.

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Metabolism/Metabolites
2-hydroxy-1-(p-sulfophenylazo)naphthalene-3,6-disulfonic acid is converted to 1-amino-2-hydroxynaphthalene-3,6-disulfonic acid in Escherichia coli and Proteus vulgaris; 1-naphthylamine-4-sulfonic acid in Escherichia coli and Proteus vulgaris.
The mechanism of reduction of sulfazoIII and amaranth red azo by the rat liver monooxygenase system was investigated. Air strongly inhibited (over 95%) the enzymatic reduction of both azo compounds; a 100% CO atmosphere inhibited the reduction of amaranth red (over 90%), but only slightly inhibited the reduction of sulfazoIII (13%). Adding 50 μM sulfazoIII to the microsomal incubation medium stimulated oxygen consumption, NADPH oxidation, and adrenaline red production, while 100 μM amaranth had no such effect. The reduction potentials of these two azo compounds also differed significantly (amaranth, E = -0.620 V; sulfazoIII, E = -0.265 V, relative to the standard hydrogen electrode). The organomercury compound methadone converted cytochrome P-450 to cytochrome P-420 (68% conversion) and significantly reduced the activity of NADPH-cytochrome P-450(c) reductase in microsomes (97% reduction), likely due to the inactivation or destruction of functional sulfhydryl groups essential for the catalytic activity of these enzymes by methadone. Glutathione (GSH) was used to restore the activity of the monooxygenase components, while NADP+ protected these components from the effects of methadone. Data showed that inactivation of NADPH-cytochrome P-450(c) reductase inhibited the reduction of sulfonyl azo III and amaranth, while inactivation of cytochrome P-450 only inhibited the reduction of amaranth. Furthermore, purified microsomal NADPH-cytochrome P-450(c) reductase reduced sulfonyl azo III at a significantly faster rate than it reduced amaranth. These studies indicate that two distinct azo reduction sites exist in the monooxygenase system, and not all azo compounds can be reduced by cytochrome P-450. The liver enzymes that reduce azo bonds play a negligible role in rat metabolism, as confirmed in experiments involving intrasplenic infusion of amaranth. Therefore, the reduction of this compound is likely influenced by intestinal bacteria. Bacterial suspensions isolated from the rat large intestine and cecum rapidly reduced amaranth. Researchers also found that rat liver homogenate and rat intestinal contents could reduce amaranth. The products of the reduction cleavage of amaranth, namely 1-amino-4-naphthalenesulfonic acid and 1-amino-2-hydroxy-3,6-naphthalenedisulfonic acid (R-amino salts), are present in the urine of rats fed with this pigment. For more complete data on the metabolism/metabolites of amaranth (6 in total), please visit the HSDB record page.

Interactions
This study investigated the effects of Allura Red AC (R40), Tartrazine (Y4), Sunset Yellow FCF (Y5), Amaranth Red (R2), and Brilliant Blue FCF (B1), alone and in combination, on neural progenitor cell (NPC) toxicity (a developmental biomarker) and neurogenesis (an indicator of adult central nervous system (CNS) function). In a developing CNS model, R40 and R2 reduced the proliferation and survival of pluripotent NPCs in mice. Among several combinations tested in mouse models, the combination of Y4 and B1 (at a dose 1000 times the average daily intake in Korea) significantly reduced the number of newly generated cells in the hippocampus of adult mice, indicating a significant adverse effect on hippocampal neurogenesis. However, other combinations, including R40 and R2, did not affect neurogenesis in the dentate gyrus of adult mice. Evidence suggests that the use of most tar food colorings, alone or in combination, may pose safety risks regarding developmental neural progenitor cells (NPCs) and adult hippocampal neurogenesis. However, the response to excessively high doses of Y4 and B1 suggests a possible synergistic effect, inhibiting NPC proliferation in the adult hippocampus. Data indicate that the combination of tar pigments may have adverse effects on both developmental and adult hippocampal neurogenesis; therefore, more extensive studies are needed to evaluate the safety of these additive combinations. One hundred mice in each group were administered 0 or 0.01 g amaranth paste (= 0.004 g amaranth) daily by gavage. One drop of 9,10-dimethyl-2-benzanthracene or 3,4-benzopyrene was applied to the interscapular skin once weekly. Papilloma onset was 3.5 weeks earlier and more numerous in the experimental group mice. The incidence of malignant tumors was higher in the experimental animals. Supplementation with 2.5% cholestyramine after adding 5% amaranth to a purified low-fiber diet counteracted the toxic effects in rats. The presence of amaranth inhibited the mutagenic activity of β-naphthylamine. Similar results were reported for α-naphthylamine, indicating that amaranth interacts with the liver activation system, preventing the conversion of amines into mutagens.

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Non-human toxicity values
Mouse intraperitoneal LD50: 1000 mg/kg
Rat intravenous LD50: 1 g/kg
Rat intraperitoneal LD50: 1 g/kg
Mouse oral LD50: >10 g/kg body weight
Rat oral LD50: 6 g/kg body weight

Amaranth red is a deep red to deep purple powder, almost tasteless with a slightly salty taste. Its pH (1% aqueous solution) is approximately 10.8. It was once used to dye wool and silk a bright blue-red in acidic dye baths. Amaranth red is an organic molecular entity. It is a sulfonylnaphthalene azo dye and was used as a colorant, dye, and chemical indicator in food and pharmaceuticals. In 1976, the U.S. Food and Drug Administration (FDA) banned its use in food, drugs, and cosmetics. (Excerpt from Merck Index, 11th edition)

C20H11N2NA3O10S3

604.4613

603.926

915-67-3

13506

Brown to reddish brown solid powder

1.5

>300°C

44ºC

6.068

1

12

2

38

1080

0

WLDHEUZGFKACJH-UHFFFAOYSA-K

InChI=1S/C20H14N2O10S3.3Na/c23-20-18(35(30,31)32)10-11-9-12(33(24,25)26)5-6-13(11)19(20)22-21-16-7-8-17(34(27,28)29)15-4-2-1-3-14(15)16;;;/h1-10,23H,(H,24,25,26)(H,27,28,29)(H,30,31,32);;;/q;3*+1/p-3

sodium (E)-3-hydroxy-4-((4-sulfonatonaphthalen-1-yl)diazenyl)naphthalene-2,7-disulfonate

Amaranth DyeE123E 123E-123Azo

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)

DMSO : ~25 mg/mL (~41.36 mM)
H2O : ~6.67 mg/mL (~11.03 mM)

Solubility in Formulation 1: ≥ 2.5 mg/mL (4.14 mM) (saturation unknown) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 400 μL PEG300 and mix evenly; then add 50 μL Tween-80 to the above solution and mix evenly; then add 450 μL normal saline to adjust the volume to 1 mL.
Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

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Solubility in Formulation 2: ≥ 2.5 mg/mL (4.14 mM) (saturation unknown) in 10% DMSO + 90% (20% SBE-β-CD in Saline) (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 900 μL of 20% SBE-β-CD physiological saline solution and mix evenly.
Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.

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