Introduction/Overview
In the field of natural product chemistry and pharmacology research, discovering small molecule compounds with clear biological activity from traditional medicinal and edible plants is one of the important strategies for modern drug development. Sesame seeds（Sesamum indicum L. As an ancient oil crop, its seeds and pressed sesame oil are not only nutritious, but also used in traditional medicine as adjunctive treatments for various diseases. Sesamol, also known as 3,4-methylenedioxyphenol, is a characteristic phenylpropanoid active ingredient in sesame oil, particularly derived from sesamolin during the refining and heating processes of sesame oil. In recent years, with the deepening development of free radical biology and oxidative stress theory, sesamin has attracted much attention due to its excellent antioxidant capacity. Numerous in vitro and in vivo studies have shown that sesamin not only directly scavenges free radicals, but also exerts multiple pharmacological activities such as anti-inflammatory, anti-tumor, neuroprotective, and cardiovascular protection by regulating core cellular defense signaling pathways. This article aims to systematically review the chemical properties, plant sources, pharmacological activities, molecular mechanisms of action, and potential medicinal properties of sesamol, in order to provide comprehensive scientific references for the deep development and clinical application of this natural product.
Chemical structure and physicochemical properties
The chemical name of sesame phenol is 3,4-methylenedioxyphenol, with a CAS number of 533-31-3, a molecular formula of C7H6O3, and a molecular weight of 138.1220. Its structural core is a benzene ring, connected to a phenolic hydroxyl group (- OH) at position 1, and bridged by a methylenedioxy group (- O-CH2-O -) at positions 3 and 4 to form a five membered oxygen-containing heterocyclic ring. This unique ortho methoxy phenol structure is the chemical basis for its high antioxidant activity. Phenolic hydroxyl is a key functional group that provides hydrogen atoms to neutralize free radicals such as DPPH, ABTS ⁺, hydroxyl radicals, etc. The adjacent methoxy group may stabilize the phenolic oxygen radical intermediate through electronic effects, thereby enhancing its free radical scavenging ability.
In terms of physicochemical properties, the lipid water partition coefficient (LogP) of sesamol is about 0.9475, indicating that it has a certain lipophilicity, but not too strong, which is beneficial for its crossing of cell membranes. Its topological polar surface area (TPSA) is 38.6900 Å ², which is a relatively small value, indicating good membrane permeability. The water solubility data is 6.8975 (usually referring to LogS or related solubility parameters, specific units need to be combined with the context, here it can be understood as moderate to low water solubility). Pure sesame phenols are white to light yellow needle shaped crystals or powders. These physicochemical parameters collectively determine the absorption and distribution characteristics of sesamin in organisms. It is worth noting that its small molecular weight and suitable lipophilicity give it a high blood-brain barrier permeability, which provides the possibility for its application in central nervous system diseases.
Plant sources and extraction methods
Sesame phenols mainly come from sesame seeds（Sesamum indicum L. The seeds of sesame oil and their processed products. In intact sesame seeds, sesamolin is not present in large quantities in free form, but is stored in the form of its glycoside precursor (such as sesamolin). During the pressing of sesame oil, especially subsequent refining processes such as degumming, deacidification, decolorization, and deodorization, as well as daily cooking and heating, sesamin undergoes molecular rearrangement and hydrolysis under the action of acid, heat, or enzymes, releasing free sesamin. Therefore, the content of sesame phenols in refined sesame oil or baked sesame products is usually higher than that in cold pressed crude oil.
Extracting and purifying sesamol from sesame oil or sesame meal is the main way to obtain this compound. Traditional methods include solvent extraction, which commonly uses organic solvents such as ethanol, ethyl acetate, petroleum ether, etc. to extract sesame oil or defatted sesame powder, and then separates and purifies it through techniques such as silica gel column chromatography and preparative high-performance liquid chromatography (HPLC). Modern extraction techniques such as supercritical CO ₂ extraction have also been applied to the extraction of sesame phenols due to their advantages of low operating temperature, no solvent residue, and good selectivity, which can better protect their activity. In addition, there have been research reports on chemical synthesis and biosynthesis methods, but natural extracts are more favored in the fields of food and health products due to their "green" label. The optimization goal of the extraction process is to improve the yield and purity of sesamin while maintaining its biological activity.
Pharmacological activity research
Numerous preclinical studies have confirmed that sesamin has broad and significant pharmacological activities, with its core centered around antioxidant activity and extending to multiple disease domains.
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antioxidant activity This is the most fundamental and prominent activity of sesamin. In vitro chemical models, such as DPPH radical scavenging experiments, the IC50 value is 5.95 ± 0.56 μ g/mL, demonstrating strong direct radical scavenging ability. In addition, it also has efficient scavenging effects on superoxide anions, hydroxyl radicals, peroxynitrite anions, etc. In cell models, sesamin can significantly alleviate oxidative damage induced by oxidants such as hydrogen peroxide (H ₂ O ₂) and tert butyl hydroperoxide (t-BHP), and improve cell survival rate.
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Antitumor activity Sesamol can inhibit the growth and promote apoptosis of many cancer cell lines, including colon cancer, breast cancer, lung cancer, liver cancer, leukemia, etc. Its function is not limited to inducing apoptosis of cancer cells, but also involves inhibiting proliferation, blocking the cell cycle (such as blocking cells in G0/G1 or G2/M phases), inhibiting migration and invasion, and resisting angiogenesis. It is worth noting that some studies suggest that sesamin has relatively low toxicity to normal cells and may have some selectivity.
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Neuroprotective activity Due to its high blood-brain barrier permeability, sesamin has shown protective effects in various animal models of neurodegenerative diseases and brain injuries. For example, in Alzheimer's disease models, it can alleviate beta amyloid induced neurotoxicity and memory impairment; In Parkinson's disease models, it can counteract dopaminergic neuron damage caused by MPTP/MPP ⁺; In models of cerebral ischemia-reperfusion injury and stroke, it can reduce the infarct size and improve neurological deficits.
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Cardiovascular protective activity Sesamol can improve atherosclerosis induced by high-fat diet, reduce serum total cholesterol, triglyceride and low-density lipoprotein levels, and increase high-density lipoprotein. It can also alleviate myocardial ischemia-reperfusion injury, inhibit myocardial cell apoptosis, and improve heart function.
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Anti inflammatory and liver protective activity Sesamol exerts anti-inflammatory effects by inhibiting the expression of pro-inflammatory factors (such as TNF - α, IL-1 β, IL-6) and the production of inflammatory mediators (such as COX-2, iNOS). In chemical (such as acetaminophen, carbon tetrachloride) or alcoholic liver injury models, sesamin can significantly reduce serum transaminase levels, alleviate liver lipid peroxidation and inflammatory cell infiltration, and protect liver cells.
Mechanism of action and molecular targets
The multiple pharmacological activities of sesamin stem from its diverse regulation of cellular signaling pathways. Its core mechanism is to activate the cell's own antioxidant defense system and indirectly affect downstream pathways such as apoptosis, inflammation, and metabolism.
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Activate Nrf2/ARE antioxidant pathway This is the most critical mechanism by which sesamin exerts antioxidant and cell protective effects. Nuclear factor E2 related factor 2 (Nrf2, encoded by NFE2L2 gene) is the main transcription factor that regulates cellular oxidative stress response. In the resting state, Nrf2 binds to its inhibitory protein Keap1 and is degraded by ubiquitination. Sesamol can dissociate Nrf2 from Keap1 by modifying the cysteine residues on Keap1, leading to translocation to the nucleus. In the nucleus, Nrf2 binds to antioxidant response elements (ARE), initiating the transcriptional expression of a series of phase II detoxifying enzymes and antioxidant proteins. The relevant targets include:
- HMOX1 Encoding heme oxygenase-1, it catalyzes the degradation of heme, producing biliverdin and carbon monoxide with antioxidant and anti-inflammatory effects.
- NQO1 NAD (P) H: Quinone oxidoreductase 1, involved in detoxification of quinone substances.
- GCLC/GCLM The rate limiting enzyme that regulates glutathione synthesis.
- SOD1(Intracellular copper zinc superoxide dismutase)SOD2(Mitochondrial manganese superoxide dismutase)CAT(Catalase)GPX1(Glutathione peroxidase 1): These are key enzymes that directly clear reactive oxygen species such as superoxide anions and hydrogen peroxide. Sesamol significantly upregulates the activity of these enzymes through the Nrf2 pathway, thereby systematically enhancing the antioxidant capacity of cells.
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Regulating apoptosis related pathways In anti-tumor effects, sesamin can regulate multiple apoptotic signaling pathways. It can upregulate pro apoptotic proteins (such as Bax, Bak) and downregulate anti apoptotic proteins (such as Bcl-2, Bcl xL), leading to a decrease in mitochondrial membrane potential, release of cytochrome C, and activation of the caspase cascade reaction. In addition, it can also inhibit survival signaling pathways such as PI3K/Akt and NF - κ B, and may activate the p53 pathway.
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Inhibition of NF - κ B inflammatory pathway Sesamol can inhibit the activity of I κ B kinase (IKK), prevent the phosphorylation and degradation of I κ B α, thereby inhibiting the nuclear translocation of NF - κ B p65 subunit, reducing the transcription of downstream pro-inflammatory cytokines and inflammatory mediators, which is the main molecular basis of its anti-inflammatory effect.
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Other mechanisms This also includes regulating the MAPK signaling pathway (such as inhibiting excessive activation of JNK and p38), inhibiting cyclooxygenase (COX) and lipoxygenase (LOX) activity, etc.
Evaluation of drug properties and pharmacokinetics
The preliminary drug like evaluation of sesamol shows that it has good potential for development. Its molecular weight (138.12) is much smaller than 500, meeting the requirements of Lipinski's "Five Rules" for oral drug molecules. The LogP value is about 0.95, which is within the ideal range (usually considered to be 1-3, and 0.95 is also acceptable), indicating that it has a balanced lipid solubility and water solubility, which is beneficial for gastrointestinal absorption and distribution in the body. The low TPSA value further supports its good membrane permeability. The preliminary screening results for critical safety are optimistic:HERG inhibition experiment is negative, indicating a low risk of potential cardiac toxicity (inducing long QT syndrome);The Ames test result is 1.2(usually expressed as mutation rate, less than 2 can be considered negative), indicating that it has no obvious mutagenicity under the experimental conditions and has a low risk of genetic toxicity.
In terms of pharmacokinetics, animal studies have provided preliminary understanding. Sesame phenol is rapidly absorbed orally and has moderate bioavailability. Studies in rats have shown that it is widely distributed in various tissues and, due to its lipophilicity and small molecule properties, can effectively penetrate the blood-brain barrier and reach effective concentrations in brain tissue, which is consistent with its significant neuroprotective activity. The metabolism of sesamol in the body mainly involves II phase binding reactions, including glucuronidation and sulfation, to form corresponding complexes, which are excreted through urine and bile. Its plasma half-life is relatively short, indicating that frequent administration or dosage form modification (such as sustained-release formulations) may be necessary to maintain stable blood drug concentrations. At present, there is a lack of systematic research on the detailed pharmacokinetic parameters of it in the human body, which is one of the key issues that need to be addressed in future clinical translation.
Clinical application prospects and prospects
Sesame phenol, as a natural active molecule with abundant sources and good preliminary safety evaluation, has broad clinical application prospects, but also faces challenges.
Potential application directions：
1. Functional foods and dietary supplements As an efficient natural antioxidant, sesamin can be directly used to develop health foods with antioxidant, anti-aging, and auxiliary blood lipid regulation functions. Sesame oil or extract rich in sesamin is already a component of healthy food.
2. Adjuvant treatment/prevention of neurodegenerative diseases For diseases such as Alzheimer's disease and Parkinson's disease that currently lack a cure, the neuroprotective effect of sesamin provides the possibility for it to be used as a disease modifier or adjuvant therapy drug. Its high BBB permeability is a huge advantage.
3. Chemotherapy prevention and adjuvant therapy for tumors Based on its anti-tumor activity and relatively low toxicity to normal cells, sesamin may be used for chemoprevention of specific cancers or in combination with conventional chemotherapy/radiotherapy to enhance efficacy and reduce side effects (such as oxidative damage).
4. Cardiovascular disease and metabolic syndrome Sesamol may play a protective role in atherosclerosis, nonalcoholic fatty liver and other diseases closely related to oxidative stress and inflammation.
5. Topical preparations By utilizing its antioxidant and anti-inflammatory properties, cosmetics or topical drugs can be developed for skin photoprotection, anti-aging, and anti-inflammatory purposes.
Challenges and Future Prospects：
1. Lack of clinical evidence At present, the vast majority of research is still in the stage of cell and animal experiments, and there is an urgent need to design rigorous clinical trials to verify its effectiveness, optimal dosage, and long-term safety in humans.
2. Formulation and delivery system optimization To improve bioavailability, prolong action time, and achieve targeted delivery, it is necessary to develop new formulation technologies such as nanoparticles, liposomes, solid dispersions, etc.
3. Deep exploration of the mechanism of action In addition to the known pathways such as Nrf2, it is necessary to use omics techniques (proteomics, metabolomics) and gene editing tools to more comprehensively reveal their functional networks and potential new targets.
4. Structural modification and derivative development By chemically modifying the phenolic hydroxyl, benzene ring, or methylenedioxy groups of sesame phenols, it is possible to obtain derivatives with stronger activity, higher selectivity, and better pharmacokinetic properties.
5. Industrialization and Standardization We need to establish a stable, environmentally friendly, and low-cost large-scale production process from sesame raw materials to high-purity sesame phenolic extracts, and establish strict quality control standards.
Conclusion
Sesamol, a natural phenylpropanoid compound derived from ancient sesame crops, has become a star molecule in the pharmacological research of natural products due to its unique chemical structure and excellent antioxidant capacity. The mechanism of action of sesamin, from directly clearing free radicals to upstream regulation of the core cellular defense pathway Nrf2/ARE, has been deeply elucidated, leading to multiple remarkable pharmacological activities such as anti-tumor, neuroprotective, cardiovascular protective, and anti-inflammatory effects. The preliminary pharmacological evaluation shows that it has good drug like properties and safety potential. Although there are still many challenges in transforming it into mature clinical therapeutic drugs, especially in the accumulation of clinical data and breakthroughs in formulation technology, sesamin undoubtedly demonstrates enormous value in the fields of preventive medicine, adjuvant therapy, and functional health product development. In the future, through interdisciplinary cooperation, deepening basic research, and promoting clinical translation, sesamin is expected to move from the traditional dining table to a broader pharmaceutical and health stage, contributing its unique strength to the human health cause.
