1. Introduction
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 [1]. 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 have only recently been investigated [2]. Curcumin (1,7-bis(4-hydroxy-3-methoxyphenyl)-1,6-heptadiene-3,5-dione), also called diferuloylmethane, is the main natural polyphenol found in the rhizome of Curcuma longa (turmeric) and in others Curcuma spp. [3]. Curcuma longa has been traditionally used in Asian countries as a medical herb due to its antioxidant, anti-inflammatory [4], antimutagenic, antimicrobial [5,6], and anticancer properties [7,8].
Curcumin, a polyphenol, has been shown to target multiple signaling molecules while also demonstrating activity at the cellular level, which has helped to support its multiple health benefits [2]. It has been shown to benefit inflammatory conditions [9], metabolic syndrome [10], pain [11], and to help in the management of inflammatory and degenerative eye conditions [12,13]. In addition, it has been shown to benefit the kidneys [14].
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 [2]. Curcuminoids have been approved by the US Food and Drug Administration (FDA) as “Generally Recognized As Safe” (GRAS) [2], and good tolerability and safety profiles have been shown by clinical trials, even at doses between 4000 and 8000 mg/day [15] and of doses up to 12,000 mg/day of 95% concentration of three curcuminoids: curcumin, bisdemethoxycurcumin, and demethoxycurcumin [16]
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| Figure 1: Chemical structure of curcuminoids (include curcumin, demethoxycurcumin, and bisdemethoxycurcumin) |
2. Health Effects of Curcumin
2.1. Anti-Inflammatory Mechanism of Curcumin
The inflammatory pathway consists of four parts: inducers, sensors, mediators and effectors. The physiological and pathological mechanisms of inflammation caused by different Inflammatory triggers are different and have not yet been clarified [17]. In general, the anti-inflammatory effects of drugs mainly include: acting on receptors and signaling pathways, regulating the response of target tissues to inflammatory mediators; reversing the effect of the medium on the target tissue; producing anti-inflammatory mediators, and so on [18]. Curcumin exerts anti-inflammatory effects by regulating inflammatory signaling pathways and inhibiting the production of inflammatory mediators (Figure 2).
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| Figure 2: The regulatory effect of curcumin on inflammatory signaling pathway. |
2.2. The effect of Curcumin on Cancer Treatment
Curcumin has been found to affect cancer cells in a variety of ways leading to the prevention of cancer formation. Its most prominent effects on cancer are summarized in Figure 3 and Figure 4
v Lung cancer: Curcumin exhibits its therapeutic potential in lung cancer treatment by acting on the Wnt/β-catenin-dependent pathway in the human lung cancer cell line A549 [19]. Curcumin also suppresses the vascular endothelial growth factor (VEGF0 and NF-κB expression in the same cell line [20]. In addition, curcumin has been shown to inhibit the expression of enhancer of zeste homolog 2 (EZH2) in lung cancer cells, which was followed by a decrease in the expression of the Notch 1 gene [21]. Curcumin also induces ROS production, thus activating the DNA damage signaling pathway [22].
v Breast Cancer: Curcumin was found to inhibit the phosphorylation of Akt, mTOR and their downstream proteins, resulting in cell cycle arrest of various breast cancer cell lines, including T47D and MCF7 [23].
v Prostate Cancer: everal in vitro studies have identified curcumin as an effective agent in the treatment of prostate cancer. Curcumin interferes with various molecular signaling pathways, including the NF-κB, mitogen-activated protein kinase (MAPK) and epidermal growth factor (EGFR) pathways [63]. Moreover, curcumin downregulates C-X-C motif chemokine ligand 1 (CXCL-1) and CXCL-2 by targeting the NF-κB pathway in androgen independent prostate cancer (AIPC) cells [24].
v Gastric Cancer: Recent evidence indicates promising anticancer effects of curcumin via its ability to inhibit several signal transduction pathways, such as the p53, Ras, Wnt-β, extracellular signal-regulated kinases (ERK), PI3K, MAPKs and protein kinase B (Akt) in gastric cancer cells [25].
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| Figure 4: Oncogenic signaling targets many levels curcumin |
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Hoang Viet Giang