Isophorone acts as a small molecule agonist of peroxisome proliferator-activated receptor gamma (PPARγ) signaling, with a bioactivity potency of 50118.7 nM according to qHTS assay data. This nuclear receptor is involved in the regulation of fatty acid storage and glucose metabolism. Beyond this receptor activity, isophorone does not have well-defined primary pharmacological targets, as it is primarily an industrial solvent and chemical intermediate rather than a therapeutic agent. Its biological interactions are largely related to its chemical reactivity as an unsaturated ketone rather than specific receptor binding.

Isophorone can be selectively oxidized to 4-hydroxyphorone, a synthetic intermediary for pigments and medicinal compounds as well as a significant flavor and aroma component. It is a good target for oxidation via biocatalysis [1].
In vitro studies on isophorone are limited due to its primary use as an industrial chemical. As a PPARγ agonist, it shows bioactivity at high micromolar concentrations (EC50 ~50 μM). However, this activity is weak compared to dedicated PPARγ ligands. In cell-based systems, isophorone may exhibit cytotoxic effects at elevated concentrations due to its ability to form reactive intermediates. Its antimicrobial properties have also been noted in preliminary studies. The compound's in vitro effects are largely attributed to its chemical reactivity as an α,β-unsaturated ketone, which can undergo Michael addition reactions with biological nucleophiles.

In vivo studies on isophorone have primarily focused on its toxicological profile rather than therapeutic efficacy. Oral, inhalation, and dermal exposure routes all demonstrate toxicity, indicating good absorption across epithelial membranes. In male rats, chronic exposure leads to the development of tumors through alpha-2u-globulin accumulation, a protein that binds to isophorone metabolites and accumulates in the kidney. This mechanism is species-specific and not considered relevant to humans. The compound is rapidly metabolized and excreted, with no significant accumulation in tissues.

In vitro enzyme/receptor binding assays for isophorone are not well established due to its primary classification as an industrial chemical. However, it has been identified as a PPARγ agonist using quantitative high-throughput screening (qHTS) methods. Such assays typically involve the use of reporter gene systems where cells are transfected with a PPARγ expression vector and a luciferase reporter plasmid. The compound is incubated with the cells, and luciferase activity is measured to determine agonist potency. For toxicological assessment, isophorone may be evaluated in enzyme inhibition studies.

Cell-based assays for isophorone are not commonly performed in a drug discovery context. When evaluated, typical protocols involve exposing cultured mammalian cells (e.g., hepatocytes or renal cells) to varying concentrations of isophorone (typically 1-100 μM) for 24-72 hours. Cytotoxicity is assessed using MTT or LDH release assays. The compound may also be tested in reporter gene assays for nuclear receptor activity, where cells are transfected with PPARγ-responsive luciferase constructs and treated with isophorone for 16-24 hours before luminescence measurement.

Animal studies with isophorone are predominantly toxicological rather than pharmacological. In standard rodent models, animals are administered isophorone via oral gavage, inhalation, or dermal application at doses ranging from 50 to 500 mg/kg. These studies assess acute toxicity, repeated-dose toxicity, carcinogenicity, and reproductive toxicity. In carcinogenicity studies, male rats develop kidney tumors after chronic exposure, attributed to alpha-2u-globulin accumulation. Such protocols typically last 2 years with daily dosing and comprehensive histopathological examination of all major organs.

Absorption, Distribution and Excretion
Isophorone has been shown to be toxic via oral, inhalation, and dermal contact, indicating its ability to cross epithelial cell membranes. In rabbits and rats orally administered isophorone, unmetabolized isophorone was excreted in both exhaled air and urine. Preliminary pharmacokinetic results show that in rats orally administered 14C-isophorone, 93% of the radiolabeled isophorone was excreted in urine, exhaled air, and feces within 24 hours. The majority of the radiolabeled isophorone was present in urine, indicating good absorption. In rats and rabbits administered 4000 mg/kg isophorone via gavage, isophorone was widely distributed in various organs within 1–5 hours, indicating rapid gastrointestinal absorption. In two rabbits, after gavage administration of 1000 mg/kg isophorone, a plasma concentration of 102 μg/L was reached within 10 minutes. After 30 minutes, the blood concentration rose to 141 μg/L, and after 21 hours it dropped to ≤0.05 μg/L. The results indicate that isophorone is rapidly absorbed and eliminated. The detection of unmetabolized isophorone and its metabolites in urine, and the observation of systemic toxicity and carcinogenicity in animals orally administered isophorone, provide qualitative evidence for the oral absorption of isophorone. In rats exposed to 400 ppm isophorone for 4 hours, sacrificed immediately, 1.5 hours, or 3 hours post-exposure, the results showed that isophorone levels reached their highest immediately after exposure in all tested tissues (brain, lung, heart, stomach, liver, spleen, pancreas, kidney, adrenal gland, testis, and ovary). The levels ranged from 1.5 to 74 μg/g tissue wet weight. Three hours post-exposure, the level of radiomarkers in male animals decreased rapidly, while the decrease in female animals was minimal.
Twenty-four hours after oral administration of 14C-isophorone from corn oil to male rats, the radiolabeled isomer was widely distributed throughout the body, with the highest levels found in the liver, kidneys, prepuce glands, testes, brain, and lungs. Following gavage administration of 4000 mg/kg isomerone to rats and rabbits, isomerone was widely distributed in their tissues. Rats died within 1–5 hours of administration, and rabbits died within 1 hour; tissue samples were collected for analysis at these times. The tissue concentrations of isomerone (μg/g wet tissue weight) in rats were as follows: stomach - 6213, pancreas - 2388, adrenal glands - 1513, spleen - 1038, liver - 613, brain - 378, lungs - 383, heart - 387, kidneys - 465, testes - 275, ovaries - 471. In rabbits, the concentrations in various tissues are as follows: stomach - 5395, adrenal glands - 1145, ovaries - 3000, spleen - 545, liver - 515, kidneys - 295, heart - 260, lungs - 50.

---

Metabolism/Metabolites
...Isophorone is metabolized in rabbits to 5,5-dimethylcyclohexyl-1-en-3-one-1-carboxylic acid, and excreted in the urine as ester glucuronide.
After oral administration of 1 g/kg α-isophorone, the urine of both rabbits and mice contained α-isophorone, isophorol, and cis-3,5,5-trimethylcyclohexanol. trans-3,5,5-trimethylcyclohexanol, dihydroisophorone, 5,5-dimethylcyclohexyl-1-en-3-one-1-carboxylic acid, and dihydroisophorone glucuronide were also present. When industrial isophorone was orally administered to rabbits, the allyl methyl group of isophorone was oxidized to a carboxylic acid group. This product was detected in the urine; no other products were identified. Rabbits and rats orally administered isophorone excreted unchanged isophorone in their exhaled breath and urine. The urine also contained 3-carboxy-5,5-dimethyl-2-cyclohexen-1-one, as well as 3,3,5-trimethyl-2-cyclohexen-1-ol (isophorol), 3,5,5-trimethylcyclohexanone (dihydroisophorone), and glucuronic acid conjugates of cis- and trans-3,5,5-trimethylcyclohexanol. The content of dihydroisophorone in rat urine was higher than that in rabbit urine, while the content of isophorol was lower. ...Some have proposed that the metabolic pathways of isophorone include: methyl oxidation to 3-carboxy-5,5-dimethyl-2-cyclohexen-1-one, keto reduction to isophorol, cyclic double bond reduction to dihydroisophorone, and disproportionation of dihydroisophorone to cis- and trans-3,5,5-trimethylcyclohexanol.
Isophorone is rapidly absorbed after oral, inhalation, or dermal exposure. It is distributed throughout the body due to its lipophilic nature, with a logP of approximately 2.0. Metabolism occurs primarily in the liver via oxidation and conjugation pathways, with metabolites excreted in urine. The compound has a relatively short half-life in biological systems, with most of the administered dose eliminated within 24 hours. Its solubility in water is low (1.2 g/L at 20°C) but it is miscible with most organic solvents, influencing its absorption and distribution characteristics.

Toxicity Summary
Identification: Isophorone is a colorless liquid with a minty odor. It is readily soluble in water and miscible with most organic solvents. Human Exposure: Low concentrations of isophorone are perceptible in humans. Irritation of the eyes, nose, and throat, as well as symptoms such as nausea, headache, dizziness, fainting, and intoxication have been observed. It can enter the human body through skin contact, inhalation, and oral ingestion via drinking water. Animal Studies: Distribution studies in rats using ¹⁴C isophorone showed that 93% of the radioactive material after oral administration appeared primarily in urine and exhaled breath within 24 hours. Subsequently, the highest concentrations of residual radioactive material were found in the liver, kidneys, and prepuce glands. The oral metabolites of isophorone detected in rabbit urine mainly originate from the oxidation of 3-methyl groups, reduction of ketone groups, and hydrogenation of the cyclohexene ring double bond. These metabolites are excreted in their original form or as (alcohol) glucuronide derivatives. Animal studies have shown that isophorone can be rapidly absorbed through the skin. Acute reactions to dermal exposure in rats and rabbits ranged from mild erythema to crusting. Direct application to the eyes or exposure to high concentrations of isophorone has been reported to cause conjunctivitis and corneal damage. In acute short-term oral studies in rodents, high doses of isophorone caused hepatic degeneration, central nervous system depression, and death in some animals. In a limited number of beagle dogs, no adverse reactions were observed at daily doses up to 150 mg/kg body weight over a 90-day oral study. Isophorone does not induce bacterial gene mutations, in vitro chromosomal aberrations, primary rat hepatocyte DNA repair, or mouse bone marrow micronuclei. Positive effects were observed only in the absence of an exogenous metabolic system in L5178YTK+/- mouse mutagenesis and sister chromatid exchange assays. In the absence of an exogenous metabolic system, isophorone can induce in vitro morphological transformation. It does not induce sex-linked recessive lethal mutations in Drosophila. In long-term oral toxicity studies in mice and rats, male rats exhibited various kidney lesions, including nephropathy, renal tubular cell hyperplasia, and a small number of renal tubular cell adenomas and adenocarcinomas. Isophorone exposure was associated with certain neoplastic lesions of the liver, skin, and lymphoreticular system in male mice, as well as non-neoplastic liver and adrenal cortex lesions, but these were not observed in female mice. In a long-term inhalation study in rats and rabbits, ocular and nasal mucosal irritation, as well as changes in the lungs and liver, were observed. Limited studies in rats and mice suggest that isophorone does not affect fertility or cause developmental toxicity in experimental animals. Central nervous system depression observed in experimental animals may indicate neurotoxicity. Isophorone also showed a positive effect in the desperate swimming behavior test. Data on terrestrial animals are currently unavailable. Existing data suggest that isophorone has low toxicity to aquatic organisms.

---

Toxicity Data
LC50 (Rat) = 7,000 mg/m3/4h
Interactions
Based on acute LD50 data from oral intubation in female albino rats, the combined toxicity of isophorone with 26 industrial liquid chemicals was investigated. …The LD50 value for each compound was determined. Based on the assumption of simple similarity, isophorone showed >additive toxicity when used in combination with 9 compounds and additive toxicity. An isotoxic mixture is defined as a mixture in which the volume of each chemical substance is proportional to its individual oral LD50 value in rats, thus each component contributes equally to the toxicity of the mixture. ...It has been reported that in mice, inhalation of isophorone 4 hours later increased the seizure threshold induced by intravenous tebuconazole...

---

Non-human toxicity values
Oral LD50 in rats: 1000-3450 mg/kg.
Dermal LC50 in rabbits: 1380 mg/kg.
Inhalation LC50 in rats: 7000 mg/m³/4 hours.
Oral LD50 in mice: 2.0 g/kg.
For more complete non-human toxicity data on isophorone (10 in total), please visit the HSDB records page.
Isophorone exhibits toxicity via oral, inhalation, and dermal exposure routes. In acute toxicity studies, the oral LD50 in rats is approximately 2-4 g/kg. Chronic exposure in male rats leads to kidney tumors through a mechanism involving alpha-2u-globulin accumulation, which is species-specific and not considered relevant to humans. Other toxic effects include irritation to the skin, eyes, and respiratory tract. The compound may also cause central nervous system depression at high doses. It is not classified as a mutagen or reproductive toxicant.

[1]. Stereoselective hydroxylation of isophorone by variants of the cytochromes P450 CYP102A1 and CYP101A1. Enzyme Microb Technol. 2018 Apr;111:29-37.

Isophorone is a clear liquid with a minty odor. It is soluble in water and evaporates slightly faster than water. It is an industrial chemical used as a solvent in some printing inks, coatings, varnishes, and adhesives. It is also used as an intermediate in the production of some chemicals. Although isophorone is an industrial chemical, it also occurs naturally in cranberries. Isophorone is a clear, colorless liquid with a camphor-like odor. It is less dense than water and insoluble in water. Its boiling point is 420 °F (216 °C). Its flash point is close to 200 °F (93 °C). Contact with it can irritate the skin and eyes. Ingestion is toxic. It is used as a solvent and insecticide. Isophorone is a cyclic ketone with the structure cyclohexyl-2-en-1-one, substituted with methyl groups at positions 3, 5, and 6. It is both a solvent and a plant metabolite. Isophorone is a cyclic ketone and an enone. It is a widely used solvent and chemical intermediate. Acute (short-term) effects of inhaled isophorone on humans include eye, nose, and throat irritation. Long-term exposure to isophorone can cause dizziness, fatigue, and depression. Animal studies have shown that long-term inhalation of high concentrations of isophorone can affect the central nervous system. Limited animal evidence suggests that isophorone inhalation during pregnancy may lead to birth defects such as fetal malformations and growth retardation. Currently, there is no information regarding the reproductive, developmental, or carcinogenic effects of isophorone on humans. The U.S. Environmental Protection Agency (EPA) has classified isophorone as a Group 7 carcinogen, meaning it is a possible human carcinogen. Isophorone has been reported to be found in Artemisia judaica, Vaccinium macrocarpon, and other organisms with available data.
Isophorone is primarily used as an industrial solvent and precursor to polymers, rather than a therapeutic drug. Its identification as a PPARγ agonist is based on high-throughput screening data, but this activity is weak and not therapeutically relevant. The compound's toxicological profile has been extensively studied due to its widespread industrial use, with the alpha-2u-globulin-mediated nephropathy in male rats being a key finding for risk assessment. It is not approved for any clinical use and remains exclusively a research chemical and industrial intermediate.

C9H14O

138.21

138.104

78-59-1

Isophorone-d5;1262769-87-8;Isophorone-d8;14397-59-2

6544

Colorless to light yellow liquid

0.9±0.1 g/cm3

215.2±0.0 °C at 760 mmHg

−8 °C(lit.)

84.4±0.0 °C

0.2±0.4 mmHg at 25°C

1.455

2.07

0

1

0

10

187

0

O=C1C([H])=C(C([H])([H])[H])C([H])([H])C(C([H])([H])[H])(C([H])([H])[H])C1([H])[H]

HJOVHMDZYOCNQW-UHFFFAOYSA-N

InChI=1S/C9H14O/c1-7-4-8(10)6-9(2,3)5-7/h4H,5-6H2,1-3H3

3,5,5-trimethylcyclohex-2-en-1-one

NSC-403657; NSC 403657; Isophorone

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

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 (~723.54 mM)

Solubility in Formulation 1: ≥ 2.5 mg/mL (18.09 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.

---

Solubility in Formulation 2: ≥ 2.5 mg/mL (18.09 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.

---

View More

Solubility in Formulation 3: ≥ 2.5 mg/mL (18.09 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.

---

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