**2. Bioactive compounds and health benefits of spices**

#### **2.1 Turmeric (***Curcuma longa* **L)**

#### *2.1.1 Bioactive compounds*

Turmeric is an orange-yellow-colored rhizomes which has been used as spice and health care additives since the ancient times. Turmeric is rich in polyphenolic compounds. Curcumin is the major polyphenolic compounds in turmeric followed by demethoxycurcumin and bisdemethoxycurcumin. Some other bioactive compounds found in the rhizome of turmeric are *α*-turmerone, and *β*-turmerone [15, 16]. Moreover, turmeric contains volatile compounds like camphor, eucalyptol, *β*-pinene phenyl propionoids, monoterpenes, sesquiterpenes, *α*-pinene, camphene, α-phellandrene, 3-carene, *β*-cymene, *β*-elemene, *α*-santalene, caryophyllene, α-farnesene, zingiberene, *β*-cedrene, *α*-bisabolol, and *β*-sesquiphellandrene [15, 16].

*Bioaccessibility, Bioavailability, Antioxidant Activities and Health Beneficial Properties of Some… DOI: http://dx.doi.org/10.5772/intechopen.109774*

#### *2.1.2 Antioxidant activities*

Various research studies indicated that turmeric possesses moderate to strong antioxidant activities due to the presence of curcuminoids. The antioxidant potential of curcuminoids arises from its structural composition with functional groups including the β-diketo group and phenyl rings containing varying amounts of hydroxyl and methoxy substituents [15, 16]. Due to its potential antioxidant activities curcumins have been reported to have significant role in maintaining oxidative stress mediated pathological conditions [15–17]. It also protects biomembranes against peroxidative damage via scavenging of free radical activities involved in the peroxidation [15–17]. For very long-time number research is carried out to oversee the mechanism of antioxidant activities of curcumin. Jovanovic et al. reported that the central methylenic group of curcumin can donate H- rather than from the phenolic group [18]. However, some other studies proposed that phenolic group of curcumin better H donor to act as strong free radical scavenger [19, 20]. In addition to the free radical scavenging pathways curcuminoids displayed antioxidant activities stimulating the activities of antioxidant enzymes such as glutathione peroxidase, superoxide dismutase, and catalase [15, 16, 21]. Moreover, curcumin displayed antioxidant activities by preventing the inhibition of Nrf2, NFĸB translocation and IĸB degradation which are involved in regulating antioxidant activity [15–17].

#### *2.1.3 Anti-inflammatory activities*

Numerous *in vitro* and *in vivo* research studies on anti-inflammatory activity of curcumin derivatives reported that curcumin exhibited anti-inflammatory activities by interacting with various biomolecules related to inflammation such as cyclooxygenase 2, phospholipase, lipoxygenase, leukotrienes, thromboxane, prostaglandins, nitric oxide, collagenase, elastase, hyaluronidase, monocyte chemoattractant protein-1 (MCP-1), interferon-inducible protein, tumor necrosis factor (TNF), and interleukin-12 (IL-12) [15, 16, 21, 22]. Curcumin suppresses the regulation of proinflammatory interleukins (IL-1, −2, −6, −8, and − 12), cytokines (tumor necrosis factor-alpha (TNF-α), monocyte chemoattractant protein-1) by causing down-regulation of janus kinase and signal transducer and activator of transcription (JAK/STAT) signaling pathway which can contribute to the anti-inflammatory activity in the brain [15, 16, 21–23].

#### *2.1.4 Anticancer activities*

Curcumins have been shown to prevent carcinogenesis by affecting many phases of cancer including development, transformation, invasion, angiogenesis, and metastasis [15, 24]. It is effective for decreasing or preventing various cancer types such as colon, pancreas, breast, prostates, and lung cancers [15, 24–28]. Curcumin has been reported to suppress the growth of tumor cells via cell proliferation pathway (cyclin D1, c-myc), cell survival pathway (Bcl-2, Bcl-xL, cFLIP, XIAP, and cIAP1), caspase activation pathway (caspase -8, -3, and -9), tumor suppressor pathway (p53, p21), death receptor pathway (DR4, DR5), protein kinase pathway, adenosine monophosphate-activated protein kinase (AMPK) pathway [27–30].

#### *2.1.5 Antidiabetic effect*

Curcumin exhibited antidiabetic activities by decreasing hepatic glucose production, suppressing inflammatory response stemming from hyperglycemia, increasing GLUT2, GLUT3, and GLUT4 gene expression, increasing glucose intake of cells, and activating AMPK [31]. It could decrease blood glucose decreasing insulin resistance. Curcumin also played significant role to control of hyperglycemia by downregulating alpha-glucosidase and alpha-amylase activity [32]. After being treated diabetic rats with curcumin the glucose tolerance and insulin sensitivity of diabetic rats were enhanced [33].
