2-Naphthol is a metabolite of naphthalene that is metabolized by CYP isoenzymes (CYP 1A1, CYP 1A2, CYP 2A1, CYP 2E1, and CYP 2F2). 2-Naphthol (10, 25, 50, and 100 μM) decreases the growth of peripheral blood mononuclear cells without causing cytotoxic effects [1].

Absorption, Distribution and Excretion
Of transdermally administered doses of 2-naphthol, 5% to 10% are recovered in urine… Metabolism/Metabolites Multiple drug-metabolizing enzyme activities were determined in liver fractions from cattle, sheep, goats, chickens, turkeys, ducks, rabbits, and rats. The pathways detected included O-demethylation of p-nitrophenol, microsomal ester hydrolysis of procaine, and glucuronidation of p-nitrophenol, as well as cytoplasmic acetylation of sulfadiazine and sulfation of 2-naphthol. For most of the enzymatic pathways measured, goats showed greater similarity to castrated rams than to cattle. An exception was UDP-glucuronyltransferase activity, which was significantly higher in goats than in any other species studied. Among poultry, chickens and turkeys were generally the most similar species. Compared to chickens and turkeys, ducks exhibited particularly low activities of arylsulfotransferase isoenzymes III and IV. Rabbits exhibit very high N-acetyltransferase activity, while sheep and goats show very low N-acetyltransferase activity. Using model substrates, the activity pathways of several drug-metabolizing enzymes in liver fractions from channel catfish and rats were determined. The investigated pathways included O-demethylation of p-nitroanisole, microsomal ester hydrolysis of procaine, glucuronidation of p-nitrophenol, cytoplasmic acetylation of sulfadiazine, and sulfation of 2-naphthol. Channel catfish liver preparations were incubated at 25°C and 37°C, respectively. At 37°C, the oxidative metabolism of p-nitrophenol in catfish was only 1/8 that in rats; at 25°C, the oxidative metabolism of p-nitrophenol in catfish was only 1/12 that in rats. Hydrolysis of procaine esters was negligible in catfish microsomes. At 37°C, the degree of glucuronidation of p-nitrophenol in catfish and rat microsomes was comparable. The activities of N-acetyltransferase and arylsulfonyltransferase in catfish cytosol were almost identical to those in rats. In catfish liver fractions, the rates of glucuronidation and sulfation were higher at 37 °C than at 25 °C. To characterize the substrate specificity of various carboxylesterase isoenzymes, we tested a series of carbonates, thiocarbonates, carbamates, and carboxylates containing α- or β-naphthol or p-nitrophenol as leaving groups as substrates for human, rat, and mouse liver microsomal esterases; we also tested rat liver microsomal hydrolases A and B. Mammalian liver esterases cleaved α-naphthol carbonates, thiocarbonates, and carboxylates more rapidly than their corresponding β-naphthol isomers. Hydrolase B consistently showed a higher hydrolysis rate for most substrates compared to hydrolase A. The carbonate moieties of α-naphthol, β-naphthol, and p-nitrophenol reduced the specific activity of the enzymes by approximately 5-fold compared to their corresponding carboxylates, but improved stability under alkaline conditions. Human and mouse liver microsomal esterase activity is five orders of magnitude lower than that of hydrolase B. The functional groups and lipophilicity of substrate structures affect the activity of mammalian esterases. The inhibitory effect of alkylamines on the activity of hydroxysteroid sulfotransferase (ST) in rat liver was investigated. Liver homogenates from Wistar rats were prepared, and cytoplasmic fractions were separated. The activities of ST on dehydroepiandrosterone (DHEA), androstenedione (AS), and 2-naphthol (2NA) were determined. Cytoplasmic fractions were separated by column chromatography. Triethylamine was used as the elution solvent in column chromatography to purify chemically synthesized adenosine 3-phosphate-5-phosphate sulfate (PAPS). PAPS inhibited the sulfation of androgens with AS and DHEA, but had no effect on the sulfation activity of cortisol and 2-NA. The sulfate donor capacity of different PAPS formulations was compared. The inhibitory effects of 14 primary, secondary, and tertiary amines on the sulfation activity of DHEA, cortisol, and 2-NA were investigated. Secondary amine di-n-butylamine and three tertiary amines, triethylamine, tri-n-propylamine, and tri-n-butylamine, all inhibited DHEA sulfation activity by 40% to 60%, regardless of sex. However, the sulfation activities of 2-NA and cortisol were not significantly affected. Lineweaver-Burk plotting analysis using partially purified hydroxysteroid sulfation activity showed that the inhibition by triethylamine followed a non-competitive inhibition pattern. These results indicate that glucocorticoid synthase (ST) appears to be distinct from hydroxysteroid synthase (ST), which is significant for the inhibition of human hepatic ST activity by anabolic steroids and tertiary amines.
For more complete metabolite/metabolite data on 2-naphthol (8 metabolites in total), please visit the HSDB record page.
2-Naphthol is a known human metabolite of naphthalene.

Toxicity Summary
Identification and Uses: 2-Naphthol is a white, bulky flake or white powder with a faint phenolic odor. Its primary uses are in the dye and pigment industry, for example, as a coupling component in azo dyes, and in the synthesis of important intermediates such as 3-hydroxy-2-naphthoic acid (BON) and its aniline derivatives (naphthol AS), 2-naphthol sulfonic acid, aminonaphthol sulfonic acid, and 1-nitroso-2-naphthol. Major pharmaceutical products based on 2-naphthol include: the antifungal drug tonaphthyl ester (prepared from phosgene and N-methyl-m-toluidine); the semi-synthetic penicillin nafcillin (prepared from 2-ethoxynaphthyl); and the anti-inflammatory drug naproxen (prepared from 2-methoxynaphthyl). It has also been used as a stimulant for treating hair loss, an insect repellent, and a disinfectant for scabies. Human Exposure and Toxicity: Large doses of 2-naphthol ointment can cause systemic side effects, including vomiting and death. Ingestion can cause kidney damage, vomiting, diarrhea, abdominal pain, syncope, convulsions, and hemolytic anemia. It has been reported that 20 scabies patients, while receiving treatment, applied 50 grams of ointment containing 7.5% 2-naphthol twice daily for two consecutive days, developing retinal congestion. Many patients developed very small white and pigmented spots on their retinas. Two patients developed vitreous opacities. Only one patient showed lens abnormalities, manifesting as a single punctate lesion in the posterior cortex. Two patients reported visual impairment, but both had abnormal eyes prior to treatment. Animal experiments: In rabbits, the most consistent ocular change after gastric instillation or skin application of 2-naphthol was the appearance of small, shiny white spots on the retina, which quickly turned into pigmentation. The number and size of these spots increased with increasing daily dosing frequency. Retinal vessels and the iris typically showed congestion. The aqueous humor was sometimes slightly cloudy, and the vitreous humor usually showed early cloudiness, but gradually became clear with continued naphthol administration. The cornea and conjunctiva were never affected. Another study reported patchy degeneration of rod and cone cells, and irregular changes in pigment content in the pigment epithelium, in the retinas of poisoned adult rabbits. Vacuoles were present in the nuclear layer, nerve fiber layer, and ciliary body epithelium. When pregnant rabbits were given 2-naphthol, their offspring developed congenital cataracts, neuroepithelial degeneration, and retinal pigment cell hypertrophy. An in vivo study aimed to investigate the biochemical pathways regulating the cataract-inducing effects of naphthol. Researchers treated male mice with naphthol or its metabolites, along with several chemical probes capable of modulating key biochemical pathways associated with naphthol bioactivation and detoxification. At dose levels of 56 or 100 mg/kg, no cataract-inducing or lethal effects of 2-naphthol were observed; however, doses of 177 and 562 mg/kg caused death in all animals within 1.5 hours. Ecotoxicity studies: As a testing system, fish embryos and juvenile fish were the most sensitive, juvenile gudgeon and arthropods showed moderate sensitivity, while algae and snails exhibited the strongest tolerance to the test compound.

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Toxicity Data
LC50 (Rat) = 2,200 mg/m3/4h

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Non-human Toxicity Values
LD50 (Mice): Intraperitoneal injection 97,500 mg/kg
LD50 (Rat): Oral administration 1960 mg/kg

[1]. Determination of cytotoxic and genotoxic effects of naphthalene, 1-naphthol and 2-naphthol on human lymphocyte culture. Toxicol Ind Health. 2014 Feb;30(1):82-9.

2-Naphthol is a naphthol with a hydroxyl group at the 2-position. It is used as an anti-nematode drug, a genotoxin, a human xenobiotic metabolite, a mouse metabolite, a human urinary metabolite, and a free radical scavenger. 2-Naphthol is a colorless crystalline solid and an isomer of 1-naphthol, differing only in the position of the hydroxyl group on the naphthalene ring. Naphthol is a naphthalene homologue of phenol, and its hydroxyl group is more reactive than that in phenol. 2-Naphthol has a wide range of uses, including as a dye, pigment, fat, oil, pesticide, pharmaceutical, fragrance, preservative, synthetic bactericide, and rubber antioxidant. The detection of 2-naphthol in urine is usually due to prolonged exposure to pesticides such as chlorpyrifos, but it can also be caused by exposure to naphthalene in old-fashioned camphor balls, fires that produce polycyclic aromatic hydrocarbons (PAHs), and tobacco smoke.
Therapeutic Uses
2-Naphthol…has been used as a stimulant for treating hair loss, an insect repellent, and a disinfectant for scabies.

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Drug Warning
Pastes containing 2-naphthol should only be used for short periods of time, and the area covered should not exceed 150 square centimeters.

144.057

135-19-3

2-Naphthol-d8;78832-61-8;2-Naphthol-d7;78832-54-9

8663

Off-white to light brown solid powder

1.2±0.1 g/cm3

285.5±0.0 °C at 760 mmHg

120-122 °C(lit.)

144.0±10.6 °C

0.0±0.6 mmHg at 25°C

1.678

2.71

1

1

0

11

133

0

O([H])C1C([H])=C([H])C2=C([H])C([H])=C([H])C([H])=C2C=1[H]

JWAZRIHNYRIHIV-UHFFFAOYSA-N

InChI=1S/C10H8O/c11-10-6-5-8-3-1-2-4-9(8)7-10/h1-7,11H

naphthalen-2-ol

NSC 2044 NSC-2044Betanaphthol NSC2044

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.

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

DMSO : ≥ 100 mg/mL (~693.63 mM)
H2O : ~1 mg/mL (~6.94 mM)

Solubility in Formulation 1: ≥ 2.5 mg/mL (17.34 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 (17.34 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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Solubility in Formulation 3: ≥ 2.5 mg/mL (17.34 mM) (saturation unknown) in 10% DMSO + 90% Corn Oil (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 corn oil and mix evenly.

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