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Year : 2020  |  Volume : 1  |  Issue : 1  |  Page : 8-11

Role of curcumin as an antioxidant

Department of Oral Medicine and Radiology, R. R. Dental College and Hospital, Udaipur, Rajasthan, India

Date of Submission31-Oct-2020
Date of Acceptance07-Dec-2020
Date of Web Publication31-Dec-2020

Correspondence Address:
Tarun Vyas
Department of Oral Medicine and Radiology, R. R. Dental College and Hospital, Udaipur, Rajasthan
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/jpcdoh.jpcdoh_1_20

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In recent years, there is an upsurge in the areas related to newer developments in prevention of diseases, especially the role of free radicals and antioxidants; free radicals are unstable chemicals formed in the body during normal metabolism or exposure to environmental toxins such as pollutants in air, food, and water. Curcumin combined with enhancing agents provides multiple health benefits. Most of these benefits can be attributed to its antioxidant and anti-inflammatory effects. Ingesting curcumin by itself does not lead to the associated health benefits due to its poor bioavailability, which appears to be primarily due to poor absorption, rapid metabolism, and rapid elimination. There are several components that can increase bioavailability. The purpose of this review is to provide a brief overview of the plethora of research regarding the health benefits of curcumin.

Keywords: Anti-inflammatory, antioxidant, curcumin, turmeric

How to cite this article:
Vyas T. Role of curcumin as an antioxidant. J Prim Care Dent Oral Health 2020;1:8-11

How to cite this URL:
Vyas T. Role of curcumin as an antioxidant. J Prim Care Dent Oral Health [serial online] 2020 [cited 2022 Jun 29];1:8-11. Available from: http://www.jpcdoh.org/text.asp?2020/1/1/8/305890

  Introduction Top

Antioxidants are molecules that are capable of protecting the human body against so-called “free radicals” and other harmful compounds that are released within the body as a result of oxidative reactions. Free radicals are generated in living systems as a part of the normal metabolic process. In addition, chemical mobilization of fat and starch under various conditions such as lactation, exercise, fever, infection, and even fasting can result in increased radical activity and damage.[1] Free radicals are oxidants in the body. These free radicals attack the healthy cells of the body, causing them to lose their structure and function. The reactive oxygen species (ROS) and free radical-mediated reactions are involved in various pathological conditions such as anemia, asthma, arthritis, inflammation, neurodegeneration against aging process, and perhaps dementia.[2] Damage caused by free radicals appears to be a major contributor to aging and to degenerative diseases of aging such as cancer, cardiovascular disease, cataracts, immune system decline, and brain dysfunction. Overall, free radicals have been implicated in the pathogenesis of at least 50 diseases.[3] The ROS including superoxide, hydroxyl radical, and hydrogen peroxide are generated in specific organelles in the cell under normal physiological conditions.[4],[5] Excessive production of these ROS beyond antioxidant defense capacity of the body can cause oxidase stress.

”Antioxidants” are substances that neutralize free radicals or their actions. Antioxidants are capable of stabilizing, or deactivating, free radicals before they attack cells.[6] Nature has endowed each cell with adequate protective antioxidant mechanisms against any harmful effects of free radicals, for example, superoxide dismutase, glutathione peroxidase, glutathione reductase, thioredoxin, thiols, and disulfide bonding are buffering systems in every cell. Antioxidants help in promoting the growth of healthy cells and protecting cells against premature and abnormal aging, help fight age-related macular degeneration, and provide excellent support for the body's immune system.[2] Antioxidants are absolutely critical for maintaining optimum cellular and systemic health and well-being.[6] Antioxidants scavenge reactive oxygen metabolites, block their generation, or enhance endogenous antioxidant capabilities.[1]

Primary sources of naturally occurring antioxidants are whole grains, fruits, and vegetables. Plant-sourced food antioxidants such as Vitamin C, Vitamin E, carotenes, phenolic acids, phytate, and phytoestrogens have been recognized as having the potential to reduce disease risk. Most of the antioxidant compounds in a typical diet are derived from plant sources and belong to various classes of compounds with a wide variety of physical and chemical properties.[7]

Antioxidant compounds in food play an important role as a health-protecting factor. A diet rich in a variety of plant-based foods provides all of the antioxidants the body needs. Research shows that vitamins, minerals, and phytochemicals from whole foods interact to boost their cancer-fighting effects. These nutrients benefit both healthy people and those fighting disease. This is why it is important to focus on eating nutrient-rich foods rather than focusing on a single nutrient in supplement form.[8]

In recent years, there is an upsurge in the areas related to newer developments in prevention of diseases, especially the role of free radicals and antioxidants. Hence, it will be pertinent to examine the possible role of “free radicals” in disease and how “antioxidants” play an important role in their prevention, especially the current status and future prospects.[1]

  Importance of Curcumiin Top

Turmeric is a spice that has received much interest from both the medical/scientific worlds as well as from the culinary world. Turmeric is a rhizomatous herbaceous perennial plant (Curcuma longa) of the ginger family.[9] The medicinal properties of turmeric, the source of curcumin, have been known for thousands of years; however, the ability to determine the exact mechanism (s) of action and to determine the bioactive components has only recently been investigated.[10] Curcumin (1,7-bis (4-hydroxy-3-methoxyphen yl)-1,6-heptadiene-3,5-dione), also called diferuloylmethane, is the main natural polyphenol found in the rhizome of C. longa (turmeric) and in others Curcuma spp.[11] C. longa has been traditionally used in Asian countries as a medical herb due to its antioxidant, anti-inflammatory,[12] antimutagenic, antimicrobial,[13],[14] and anticancer properties.

Curcumin is being recognized and used worldwide in many different forms for multiple potential health benefits. For example, in India, turmeric – containing curcumin – has been used in curries; in Japan, it is served in tea; in Thailand, it is used in cosmetics; in China, it is used as a colorant; in Korea, it is served in drinks; in Malaysia, it is used as an antiseptic; in Pakistan, it is used as an anti-inflammatory agent; and in the United States, it is used in mustard sauce, cheese, butter, and chips as a preservative and a coloring agent, in addition to capsules and powder forms. Curcumin is available in several forms including capsules, tablets, ointments, energy drinks, soaps, and cosmetics.[10]

Oral cancer is the sixth most common form of cancer worldwide. Its incidence is particularly high in India, other Asian countries, and in certain places in the Western hemisphere, for example, parts of France and Brazil, where smoking and alcohol consumption are major risk factors. In India, the chewing and smoking of tobacco products in various forms is primarily responsible for the high incidence.

The World Health Organization has estimated that 90% of oral cancers in India among men are attributable to chewing and smoking habits.[15] About 48.2% of cancers in men and 20.5% of cancers in women are related to tobacco, a major proportion of which is in the oral cavity, pharynx, larynx, and esophagus (74.7%), while lung cancers account only for 15%. Control of cancers of the head and neck, lung, cervix, and breast, which account for 50%–55% of the cancer load in India, will thus have a measurable effect on the incidence of cancer.

Oral squamous cell carcinoma develops through a multistep process of genetic, epigenetic, and metabolic changes resulting from exposure to carcinogens. The initial presence of a precursor subsequently developing into cancer is well established in oral cancer. Oral leukoplakia and submucous fibrosis are two major precancerous lesions, but only 8%–10% of these lesions ultimately become malignant.[16] The ability to clinically predict malignant transformation is limited and routine histopathological diagnosis has limited prognostic value. The presence of epithelial dysplasia is an important parameter used in the prognostication of leukoplakia. However, there are limitations in its usage; the diagnosis is essentially subjective, all lesions exhibiting dysplasia do not eventually become malignant and some may even regress, and carcinoma can develop from lesions in which epithelial dysplasia was not diagnosed in previous biopsies. Therefore, it is necessary to develop other methods for predicting the malignant potential of premalignant lesions and preventive measures.

Free radical-mediated lipid peroxidation is involved in various cancers, and several studies have described the role of free radicals in oral cancers. Low salivary lipid peroxidation products such as malonaldehyde (MDA) and 8-hydroxydeoxyguanosine (8-OHdG) have also been reported in oral cancer.[17] Increases in lipid peroxidation products and decreases in antioxidant activity in cancer have been reported in the literature, and randomized controlled trials have shown that antioxidant (Vitamins C and E) supplementation may be beneficial in the prevention of cancer. Various research over the past half-century has indicated that curcumin (also called diferuloylmethane), a yellow coloring agent present in turmeric, is an antioxidant more potent than <Symbol>α</Symbol>-tocopherol. Curcumin has been linked with the suppression of mutagenesis and has been used as a chemopreventive agent in a wide variety of cancers, including those of the colon, breast, prostate, esophagus, lung, and oral cavity, as well as in inhibition of atherosclerosis and inhibition of viral and bacterial growth.[18]

It has been demonstrated that curcumin downregulates (khaini) or NNK-induced nuclear factor-kappa B and cyclooxygenase-2 in oral premalignant and cancer cells in vitro. In the study, they hypothesized that curcumin may suppress or prevent oral precancerous and cancerous lesions and conditions by inhibiting free radicals. To test this hypothesis, they examined the effects of curcumin in patients with leukoplakia, oral submucous fibrosis, and lichen planus by measuring salivary and serum levels of MDA, 8-OHdG, and Vitamins C and E, before and after curcumin administration. Serum and salivary Vitamin C and E levels were found to increase, while MDA and 8- OHdG levels decreased in oral leukoplakia, submucous fibrosis, and lichen planus patients after intake of curcumin, as compared to pretreatment levels. Furthermore, the changes in these values were found to be significant after clinical cure. Pain and lesion size diminished significantly in oral leukoplakia, submucous fibrosis, and lichen planus, while in submucous fibrosis, mouth opening recovered significantly. The results suggest that curcumin significantly increases the local and systemic antioxidant status and the levels of Vitamins C and E, while it decreases the lipid peroxidation and DNA damage of patients with precancerous lesions. This could be due to curcumin-induced production of Vitamins C and E and preventive DNA damage by decreasing the oxidation stress. This suggests that the anti-precancerous effects of curcumin are mediated through pro-oxidant and antioxidant pathways.

The mechanisms by which curcumin mediates its prooxidant effects remain unclear. It has been suggested that mitochondria play a role in curcumin-induced apoptosis. It is possible that curcumin activates the mitochondrial enzymes that lead to the production of ROS. The induction of ROS by curcumin may occur through its interaction with thioredoxin reductase, thus altering its activity to NADPH oxidase, which could then lead to the production of ROS.[19] There have also been reports suggesting that curcumin quenches ROS production and thus acts as an antioxidant, while others have reported that curcumin quenches ROS production at low concentrations and induces ROS production at high concentrations.[20]

It has also been stated that micronutrients enhance the levels of Vitamins A and C, as well as selenium, in the supplemented groups, with a concomitant regression of precancerous lesions present on the palate. They did not record any treatment-related toxic effects at doses up to 8 g/d, as reported previously.[21] The oral leukoplakia, submucous fibrosis, and lichen planus were cured in almost the same period of time. The antioxidant status of healthy subjects also improved with curcumin intake. Median salivary and serum MDA, 8-OHdG, and Vitamin C and E levels changed in precancerous patients before intake of curcumin and after clinical cure, and after 209 days in healthy subjects, although the changes were higher in precancerous patients. A significant correlation was observed in serum and salivary markers in all groups.

As saliva can be easily collected in a noninvasive manner, measurement of salivary disease biomarkers may prove vital in early detection of oral cancer risk. Moreover, salivary analysis for oral diagnosis may prove to be a cost-effective method for screening large populations. Curcumin has shown worldwide used for its complete benefits for health, which appear to act primarily through its antioxidant and anti-inflammatory mechanisms, anticancer, and antiandrogenic effects.[22] The administration of piperine with curcumin may enhance the efficacy of curcumin on antioxidant defense system. The findings suggest the use of curcumin as a cheap and safe adjunct therapy in individuals with oxidative-associated metabolic or neurological diseases.[23] Furthermore, regarding its constituents' bioavailability and drug delivery systems, developing modern formulations (e.g., nanoparticles, liposomes, and microspheres) and assessing their efficacy are suggested.[24]

  Conclusion Top

Curcumin has gained worldwide recognition for its various health benefits, which tend to function mainly through its anti-oxidant and anti-inflammatory mechanisms. These advantages are best accomplished when curcumin is paired with agents such as piperine, which improves its bioavailability significantly. Research suggests that curcumin can help in the treatment of oxidative and inflammatory conditions. Further studies are needed in larger samples to establish the relationship between curcumin, biomarkers, and oral cancer and to further contribute to the understanding of the mechanisms of action.

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Conflicts of interest

There are no conflicts of interest.

  References Top

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