Introduction

Turmeric is a perennial (Curcuma longa) of the ginger family and the source of curcumin, the major active ingredient in the curcuminoid family. The therapeutic properties of turmeric have been known for millennia and primarily attributable to its antioxidant and anti-inflammatory properties. A polyphenol antioxidant, curcumin is well known in Asia for its anti-inflammatory, antimutagenic, antimicrobial, and anticancer properties. Besides, it alleviates the symptoms of metabolic syndrome (MetS), pain and degenerative eye conditions. Despite established benefits, gastrointestinal absorption is poor. An active ingredient in black pepper, piperine, increases absorption 20-fold. Turmeric has diverse applications. It is widely used in Indian cuisine. In Japan, it is served in tea whereas the in Thais used it in cosmetics and food. It is used as drink flavorant in Korea. Whereas in Malaysia, it is used as an antiseptic, in Pakistan, it is used as an anti-inflammatory agent.[1]

Mechanisms of Action

Antioxidant

By virtue of its antioxidant and anti-inflammatory capacity, curcumin exert its therapeutic effects. Among some of the antioxidant effects are increasing the activity of three major enzymes. They are superoxide dismutase (SOD) catalase and glutathione peroxidase (GSH). In concert with GSH, catalase and SOD, curcumin neutralizes the ROS/RNS species of free radicals. Also inhibited by curcumin are the ROS-generating enzymes lipoxygenase/cyclooxygenase and xanthine hydrogenase/oxidase. In addition, curcumin is an efficient scavenger of peroxyl radicals. Among them are the superoxide (O2-.) and hydroxyl (.OH) radicals. These potentially cause lipid peroxidation which is deleterious to proteins, DNA and cell membrane.[2]^,[3]

Anti-Inflammatory

Oxidative stress is the underlying cause of several chronic diseases. Their pathologies are causally related to inflammation which demonstrably triggers conditions such conditions as Alzheimer’s disease (AD), Parkinson’s disease, colitis, arthritis, psoriasis, diabetes, obesity, multiple sclerosis, epilepsy, cardiovascular disease, cancer, allergy, asthma, bronchitis, depression and fatigue. Inflammatory cells are known to liberate free radicals at the site of inflammation suggesting a cause-effect relationship between oxidative stress and inflammation. In addition, a number of ROS/RNS free radicals stimulate the release of pro-inflammatory factors. Prominent among them is tumor necrosis factor α (TNF-α)[4] which activates NF-κB, another inflammatory factor. But NF-κB is also activated by a host of other factors: namely, gram-negative bacteria, viral pathogens, environmental pollutants, psychological stress, high sugar levels, fatty acids, UVR and cigarette smoke. It is, therefore, logical to infer that suppression NF-κB would be effective against several inflammatory diseases. Among naturally occurring compounds that has been shown to block NF-κB is curcumin [5]. Well-known chronic inflammatory diseases are osteoarthritis (OA) and rheumatoid arthritis. Once considered a degenerative and non-inflammatory, osteoarthritis is now recognized as an inflammatory condition having elevated cytokine levels, as well as being connected to systemic inflammation. Turmeric dosages of 1000 mg/day has been found to reduce arthritis symptoms.

Metabolic Syndrome

Metabolic syndrome (MetS) is a cluster of symptoms often manifested as CVDs, type 2 diabetes, hypertension, high blood sugar, excess visceral fat, low HDL but high LDL and triglyceride levels. People afflicted with this condition also suffer from excessive blood clotting and chronic low-grade inflammation. Contributory conditions are fatty livers, polycystic ovarian syndrome, gallstones and breathing problems during sleep[6]. Because of its ability to neutralize oxidative stress, curcumin is capable of improving insulin sensitivity, suppressing fat-cell multiplication, reducing hypertension and inflammation. In addition, curcuminoids – the entire family of active compounds within turmeric - decreases circulating triglycerides and total cholesterol but elevate good cholesterol. MetS patients on diets supplemented with a curcuminoid-piperine[7], showed reduced levels of oxidative stress, inflammation and C-Reactive Protein (CRP). The latter is a marker of inflammation and indicative of several disease conditions including cancer. High CRP levels is also an indicator of inflammation in the arteries of the heart.

Chronic low-grade inflammation is a common feature of overweight/obese people. Dietary intake of curcumin demonstrably reduces the secretion of pro-inflammatory factors. It raises good cholesterol while diminishing bad cholesterol, triglycerides and lipoprotein a (Lp(a) - a risk factor for atherosclerosis, coronary heart disease and stroke. In overweight/obese subjects treated with curcumin, significant reduction in malonaldehyde (MDA) and C-reactive protein (CRP) concentrations were observed. Under normal conditions, MDA readily interacts with proteins, lipoproteins, DNA, and RNA causing cellular injury. MDA is involved in the induction of type-2 diabetes, aging and neurodegenerative diseases. Excessive MDA reduces blood flow to the brain. This situation leads to poor oxygen supply causing death of brain tissue, impairment of vision, body movement and speech[8]. Because MDA interacts with collagen, it hastens skin-wrinkling and other aging features. Moreover, dietary supplementation with curcumin improves SOD activities which is known to diminish the accumulation harmful free radicals generated during normal metabolism[9].

Effect of Curcumin on Healthy Individuals

In healthy adults, 80 mg curcumin/day has induced improvement in the profile of nitric oxide (NO): a vasodilator, causing the vessels to distend increasing blood flow and lowering blood pressure. The test group, given curcumin, also showed an increase in catalase activity thereby increasing the neutralizing potential of free radicals. In addition, curcumin intake decreased beta amyloid plaques which augurs well for those predisposed to Alzheimer’s disease. In an older group, over 60 years, 80 mg curcumin was shown to improve sustained attention, memory and mood. Curcumin-piperine supplementation reduced muscle soreness after an intense workout in rugby players. Players who received up to 1.0 g of curcumin reported less muscular pain. MRI evidence revealed less muscle injury and inflammation in athletes taking this dosage. Of significance is that curcumin is found abundantly in beets, garlic, dark chocolate, leafy greens, citrus fruits and pomegranate[10].

References

[1] Jane Higdon, Victoria J. Drake, Barbara Delage, Lynne Howells. 2005-2016. Linus Pauling Institute. Curcumin.

[2] https://www.sciencedirect.com/topics/pharmacology-toxicology-and-pharmaceutical-science/peroxy-radical

[3] https://en.wikipedia.org/wiki/Hydroperoxyl

[4] Tumor Necrosis Factor alpha (TNF-α): an inflammatory factor produced by macrophages/monocytes during acute inflammation leading to necrosis or apoptosis. It triggers the release of several immune factors, including interleukin-1 and interleukin-6 which can cause inflammatory diseases, including arthritis.

[5] Anlys Olivera, Terry W. Moore, Fang Hu, Andrew P. Brown, Aiming Sun, Dennis C. Liotta, James P. Snyder, Younghyoun Yoon, Hyunsuk Shim, Adam I. Marcus, Andrew H. Miller, and Thaddeus W. W. Pacea. 2012. Feb; 12(2): Inhibition of the NF-κB signaling pathway by the curcumin analog, 3,5-Bis(2-pyridinylmethylidene)-4-piperidone (EF31): anti-inflammatory and anti-cancer properties. Int. Immunopharmacol. 368–377.

[6] https://www.nhlbi.nih.gov/health-topics/metabolic-syndrome

[7] Piperine: The bioactive compound found in black pepper. It is also the active component found in chili powder and cayenne pepper. It has been shown to help relieve nausea, headaches and poor digestion. Of utmost significance is its ability to boost the absorption of curcumin.

[8] https://en.wikipedia.org/wiki/Brain_ischemia Retrieved October 29 2020

[9] https://www.sciencedirect.com/topics/medicine-and-dentistry/malonaldehyde Retrieved October 29 2020

[10] Susan J. Hewlings, and Douglas S. Kalman. 2017. Curcumin: A Review of Its’ Effects on Human Health. . Foods.

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