In A549 cells, thymol (20 μM, 24-48 hours) affects the expression of IL4I1 (24 hours) and the aromatic channel receptor (AHR) signaling pathway (48 hours) [2]. Thymol (5 μM, 48 hours) A549 Thymol (0-600 μM, 48 hours) modulation suppresses the epithelial-to-mesenchymal transition, motor activity, and cell proliferation in several binary types (Cal27, SCC4, SCC9, HeLa, H460, MDA-231, and PC3 cells) [2]. In A, thymol (200 μg/mL) causes conidia acetone that is reliant on caspase. flavus [4].

In an orthotopic mouse lung adenocarcinoma (LUAD) model, thymol (75 mg/kg, i.p.) alone and in combination with anti-PD-1 antibody (10 mg/kg, i.p.) both decrease LUAD progression and make animals more susceptible to anti-PD-1 antagonist therapy [2]. In Cal27-derived xenograft mice, thymol (4.3 mM in 50 μL of sterile saline, intratumoral injection, daily) demonstrated anticancer efficacy.

Western blot analysis [2]
Cell Types: A549 cells
Tested Concentrations: 20 μM incubation.
Incubation Duration: 48 h
Experimental Results: Inhibition of IL4I1 protein levels and AHR nuclear translocation. diminished overall AHR level.

Animal/Disease Models: Orthotopic mouse LUAD model [2]
Doses: Thymol 75 mg/kg, anti-PD-1 antibody 10 mg/kg
Route of Administration: anti-PD-1 antibody: intraperitoneal (ip) injection, once every 1 week. Day 5 after tumor injection. Thymol: intraperitoneally (ip) (ip), every 2 days starting on day 5 after tumor injection.
Experimental Results: Inhibited the progression of LUAD and improved the survival rate of mice. Reduce IL4I1 levels in tumors. Improve the efficacy of anti-PD-1 antibodies.

Absorption, Distribution and Excretion
Aromatic herbs are increasingly attracting attention as animal feed additives, but data on the metabolism of aromatic compounds in animals is very scarce. This study used thyme (Thymus vulgaris, leaves and flowers only, excluding stems) as a raw material to feed broiler diets. Five groups of broilers were fed thyme at addition levels of 0%, 0.1%, 0.2%, 0.3%, and 1% (w/w) for 35 days. Solid-phase microextraction-gas chromatography/mass spectrometry was used to determine the growth performance of the animals and the concentration of thymol, the main essential oil component of thyme, in intestinal contents, plasma, liver, and muscle tissue. There were no significant differences in feed intake, daily weight gain, feed conversion ratio, and slaughter weight among the groups. Thymol was detected in intestinal contents, plasma, liver, and muscle tissue. Compared with other groups, the intestinal thymol concentration was significantly higher in the group with 1% thyme (P<0.05). The thymol content in liver and muscle tissue is close to the limit of quantification. Data indicate that thyme has no positive effect on animal production performance. When high doses of thyme are added to the diet, the concentration of thymol in intestinal contents and plasma increases, but the concentration in edible tissues such as liver and muscle remains low. Thymol is readily absorbed from the gastrointestinal tract after oral administration. It is primarily excreted in the urine within 24 hours of absorption. Only a small amount of the absorbed substance is excreted in the urine as hydroxylated compounds. Thymol is primarily excreted in its original form and in the form of glucuronide and sulfate conjugates. Substituted monophenols, such as thymol…are found in plant essential oils, especially thyme essential oil, where they…are conjugated with glucuronic acid and sulfate. Known human metabolites of thymol include p-cymene-8-en-3-ol, p-cymene-2,3-diol, thymol sulfate, thymol O-glucuronide, and thyquinone.

Toxicity Summary
Identification and Uses: Thymol forms colorless crystals, usually large, or as a white crystalline powder. It is used as an insecticide (pesticide, fungicide, rodenticide, antimicrobial agent); also in fragrance manufacturing; as a fungicide; for microscopic examination; as a preservative; an antioxidant; a flavoring agent; and as a laboratory reagent. Thymol is included in a U.S. Food and Drug Administration (FDA)-approved over-the-counter drug as an antimicrobial and antifungal agent and is approved as an excipient. Human Exposure and Toxicity: Given the wide range of uses of thymol, primary skin irritation and sensitization are caused in humans, alone or as an ingredient in compound preparations, in very rare cases. Thymol is a mild local irritant. Its systemic effects are similar to phenol, but less toxic, partly due to its lower solubility. It can cause stomach pain, nausea, vomiting, central nervous system hyperactivity (e.g., polyphagia), and occasionally seizures, coma, and cardiopulmonary failure. Thymol has no genotoxicity against the human colon cancer cell line Caco-2. Animal studies: Acute oral administration of thymol is harmful, while acute dermal administration is virtually non-toxic. In rabbits, thymol is corrosive to the skin and eyes. Rats tolerated 10,000 ppm of thymol after 19 weeks of subchronic administration in their diet. Thymol did not increase the incidence of spontaneous lung tumors in mice. In chicken embryos, injection of thymol into the yolk sac or cyst resulted in various malformations. In vivo studies showed that oral administration of thymol did not induce micronuclei in mice, even at toxic doses. Thymol did not exhibit mutagenic effects in the Salmonella/microsome assay. However, thymol has been reported to be positive in the UDS (liquid scintillation counting) assay and the SCE assay in Syrian hamster embryonic cells. Although no strict dose-response relationship was found, these results were statistically significant. Other effects of thymol include cytotoxicity, antitumor activity, antibacterial activity, fungicide activity, anti-inflammatory activity, antispasmodic activity, and other pharmacodynamic effects. Ecotoxicity Study: Researchers investigated the effects of thymol on olfactory memory and brain gene expression in bees previously exposed to thymol. The results showed that the bees' specific responses to the conditioned stimulus disappeared 24 hours after learning. The study also indicated that genes encoding thymol cellular targets can be rapidly regulated after exposure to the molecule. Beekeepers use essential oils (including thymol) to control Varroa mites infesting bee colonies.

---

Interactions
This study used the human hepatocellular carcinoma cell line HepG2 to investigate the protective effect of thymol (TOH) against HgCl2-induced cytotoxicity and genotoxicity. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazol bromide (MTT) assay confirmed that TOH pretreatment effectively reduced HgCl2-induced cytotoxicity. TOH pretreatment inhibited HgCl2-induced genotoxicity, mitochondrial membrane depolarization, oxidative stress, and mitochondrial superoxide levels. Interestingly, thymol alone (TOH, 100 μM) increased basal intracellular glutathione S-transferase (GST) levels, and TOH pretreatment eliminated the decreases in glutathione, GST, superoxide dismutase, and catalase levels even after HgCl₂ poisoning. Furthermore, TOH inhibited HgCl₂-induced apoptosis and necrosis, as confirmed by flow cytometry analysis of Annexin-FITC/propidium iodide double-stained cells. These results clearly demonstrate that TOH has a cytoprotective effect against HgCl₂-induced toxicity, which may be attributed to its ability to scavenge free radicals, thereby helping to reduce oxidative stress and mitochondrial damage, and ultimately inhibiting cell death. Thymol is a natural monoterpene phenol, mainly found in thyme, oregano, and orange peel. Studies have shown that it possesses anti-inflammatory properties both in vivo and in vitro. This study investigated the anti-inflammatory effects of thymol on lipopolysaccharide (LPS)-stimulated mouse mammary epithelial cells (mMECs). mMECs were stimulated with LPS in the presence or absence of thymol (10, 20, 40 μg/mL). The concentrations of tumor necrosis factor-α (TNF-α), interleukin (IL)-6, and IL-1β in the culture supernatant were determined by enzyme-linked immunosorbent assay (ELISA). The expression levels of cyclooxygenase-2 (COX-2), inducible nitric oxide synthase (iNOS), extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK), nuclear factor-κB (NF-κB), and NF-κB inhibitor (IκB) were detected by Western blot. The results showed that thymol significantly inhibited the production of TNF-α and IL-6 in LPS-stimulated mMECs. Furthermore, thymol also inhibited the expression of iNOS and COX-2 in a dose-dependent manner. More importantly, thymol blocked the phosphorylation of IκB, NF-κB p65, ERK, JNK, and p38 mitogen-activated protein kinase (MAPK) in LPS-stimulated mMECs. These results indicate that thymol exerts its anti-inflammatory effect in LPS-stimulated mMECs by interfering with the activation of the NF-κB and MAPK signaling pathways. Therefore, thymol may be a potential therapeutic agent for mastitis.

---

Non-human toxicity values
Oral LD50 in rats: 980 mg/kg
Oral LD50 in mice: 640 mg/kg
Intravenous LD50 in mice: 100 mg/kg
Dermal LD50 in rats: >2000 mg/kg

[1]. Antibacterial and antifungal activities of thymol: A brief review of the literature. Food Chem. 2016 Nov 1;210:402-14.

[2]. Thymol targeting interleukin 4 induced 1 expression reshapes the immune microenvironment to sensitize the immunotherapy in lung adenocarcinoma. MedComm (2020). 2023 Aug 30;4(5):e355.

[3]. Thymol inhibits oral squamous cell carcinoma growth via mitochondria-mediated apoptosis. J Oral Pathol Med. 2018 Aug;47(7):674-682.

[4]. Thymol Induces Conidial Apoptosis in Aspergillus flavus via Stimulating K+ Eruption. J Agric Food Chem. 2018 Aug 15;66(32):8530-8536.

Thymol is a phenolic compound, a natural monoterpene derivative of cymene. It is a volatile oil component. It belongs to the phenolic and monoterpene classes. It is derived from the hydride of cymene. Thymol is a phenolic compound extracted from thyme oil or other volatile oils. It can be used as a stabilizer in pharmaceutical preparations. It has been used for its antiseptic, antibacterial, and antifungal properties, and was previously used as an insect repellent. (Dorland, 28th edition) Thymol has been reported in Australian erythrorhizon (Acanthospermum australe), hops (Humulus lupulus), and other organisms with relevant data. Thymol is a phenolic compound extracted from thyme oil or other volatile oils and can be used as a stabilizer and preservative (antibacterial or antifungal agent) in pharmaceutical preparations. See also: Paeonia suffruticosa root (partial); Lysimachia christinae root (partial); Eucalyptol; Thymol (component)... See more...

---

Mechanism of Action
We assessed the important role of the natural compound thymol in regulating macrophage activity by measuring all the sequential steps involved in phagocytosis. We found that spleen cell proliferation was significantly increased in the presence of thymol, and thymol was shown to be a good mitogen. Thymol treatment enhanced macrophage uptake due to increased cell membrane fluidity, and also increased macrophage lysosomal activity. Superoxide anion generation data indicated that thymol is involved in the respiratory burst, as it enhanced this property of macrophages at a concentration of 150 μM. Compared with lipopolysaccharide-treated cells, the secretion levels of TNF-α, IL-1β, and PGE₂ in the thymol-treated group decreased to 154 pg/mL, 736.1 pg/mL, and 151 pg/mL, respectively, while the levels of these cytokines were significantly increased in the lipopolysaccharide-treated group. We also determined the anticomplement activity of thymol, which was found to be more effective than rosmarinic acid. Therefore, the results of this study suggest that thymol may serve as a natural immunostimulant for the treatment of various immune diseases.

---

Therapeutic Uses
Anti-infective; Topical anti-infective; Antifungal
Exploratory Therapy: Thymol is a naturally occurring monocyclic phenolic compound derived from thyme (Lamiaceae family), and has been reported to possess anti-inflammatory properties both in vivo and in vitro. However, the mechanism of action of thymol remains unclear. This study aimed to investigate the effects of thymol on ovalbumin (OVA)-induced allergic inflammation in mice with asthma and its mechanism of action. A mouse asthma model was established using OVA induction. One hour before OVA challenge, mice were orally administered thymol at doses of 4, 8, and 16 mg/kg body weight, respectively. Twenty-four hours after the last challenge, mice were sacrificed, and data were collected using various experimental methods. Results showed that thymol pretreatment reduced ovalbumin (OVA)-specific IgE levels, inhibited the recruitment of inflammatory cells to the airways, and decreased the levels of IL-4, IL-5, and IL-13 in bronchoalveolar lavage fluid (BALF). Furthermore, thymol pretreatment significantly improved lung tissue pathology and effectively inhibited goblet cell proliferation. Additionally, thymol reduced the development of airway hyperresponsiveness and blocked NF-κB pathway activation. All data suggest that thymol may improve airway inflammation in OVA-induced asthma in mice by inhibiting NF-κB activation. These findings suggest that thymol may be a potential alternative treatment for allergic asthma.
Exploring treatments for obesity has become a global health problem. Most synthetic anti-obesity drugs have failed to effectively control obesity due to poor efficacy or significant side effects. Therefore, research on the main chemical components in herbal medicines used to treat obesity has greatly increased. The main objective of this study was to investigate the effects of thymol on a high-fat diet (HFD)-induced obesity model in mice. Male Wistar rats were fed HFD for 6 weeks to induce obesity. Subsequently, the HFD-fed rats were orally administered thymol (14 mg/kg) twice daily for 4 weeks. Changes in body weight gain, visceral fat pad weight, and serum biochemical parameters were assessed. At the end of the study, compared with rats fed a normal diet, the HFD-fed rats showed significantly higher levels of body weight gain, visceral fat pad weight, blood lipids, alanine aminotransferase (ALT), aspartate aminotransferase (AST), lactate dehydrogenase (LDH), blood urea nitrogen (BUN), glucose, insulin, and leptin (p<0.001). Thymol treatment significantly reduced body weight gain, visceral fat pad weight, blood lipids, ALT, AST, LDH, BUN, glucose, insulin, and leptin levels in HFD-induced obese rats (p<0.001). Furthermore, thymol treatment significantly reduced serum lipid peroxidation levels and increased antioxidant levels in HFD-induced obese rats. Thymol prevents HFD-induced obesity in mouse models through multiple mechanisms, including reducing visceral fat accumulation, lowering blood lipids, improving insulin and leptin sensitivity, and enhancing antioxidant capacity.
Exploratory Treatment: Mast cells play a crucial role in inflammatory skin diseases by releasing pro-inflammatory mediators; however, therapies directly targeting these cells are rare. In 1878, the topical application of thymol (a now recognized potent agonist of transient receptor potential channels) to treat eczema and psoriasis was first described. This study aimed to determine the mechanism by which thymol alters skin inflammation. Methods: This study used a mast cell-dependent passive cutaneous anaphylaxis (PCA) model and cultured mast cells in vitro to investigate the effects of topical thymol on IgE-dependent responses. Results showed that topical application of thymol 24 hours before antigen stimulation dose-dependently inhibited PCA, but direct application of thymol induced ear swelling. This direct effect is associated with local mast cell degranulation and disappears in histamine-deficient mice. However, unlike the PCA response, delayed swelling was not observed. In vitro experiments showed that thymol directly triggers intracellular calcium ion influx in mast cells via transient receptor potential channel activation, accompanied by degranulation and cytokine transcription. However, no cytokine protein production was observed. Conversely, thymol significantly increases apoptosis, a phenomenon observed both in vitro and in vivo. The authors suggest that thymol's efficacy in reducing IgE-dependent responses is achieved by promoting mast cell activation-induced apoptosis, which may explain the clinical benefits observed in earlier clinical reports. For more complete data on the therapeutic uses of thymol (8 in total), please visit the HSDB record page.

C10H14O

150.22

150.104

89-83-8

Thymol-d13;1219798-93-2

6989

White to off-white solid powder

1.0±0.1 g/cm3

233.0±0.0 °C at 760 mmHg

48-51 °C(lit.)

102.2±0.0 °C

0.0±0.4 mmHg at 25°C

1.523

3.28

1

1

1

11

120

0

MGSRCZKZVOBKFT-UHFFFAOYSA-N

InChI=1S/C10H14O/c1-7(2)9-5-4-8(3)6-10(9)11/h4-7,11H,1-3H3

5-methyl-2-propan-2-ylphenol

NSC-11215; NSC 11215; Thymol

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 : ~125 mg/mL (~832.11 mM)

Solubility in Formulation 1: ≥ 2.08 mg/mL (13.85 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 20.8 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: ≥ 2.08 mg/mL (13.85 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 20.8 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: ≥ 2.08 mg/mL (13.85 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 20.8 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.)