**2. Turmeric**

Turmeric (rhizome of *Curcuma longa* L.), native to Tropical South Asia, is used as a condiment, food preservative and a traditional remedy for various diseases. This spice of Zingiberaceae family is widely cultivated in tropics and is known by different names such as Haldi, bhadra, pitika, mehagni, terre merite etc. To date various compounds of turmeric have been identified such as monoterpenes, sesquiterpenes, curcuminoids, alkaloids, sterols. Among these, most abundant is curcumin (77%) which is responsible for characteristic yellow color of turmeric and exhibits a wide spectrum of biological effects viz. antidiabetic, antimicrobial, anti-inflammatory, etc. (**Figure 1**) [9].

Anti-inflammatory and antioxidant effects of curcumin have proved to be beneficial against neurological diseases. Curcumin has the ability to bind amyloid β (Aβ) inhibiting fibrils formation [10] and, also enhance its cellular uptake [11], circumvent plaque deposition [12] thereby preventing Alzheimer's disease. Furthermore, curcumin is capable of decreasing Aβ serum levels and attenuating inflammation in Alzheimer's disease mouse models [13] along with rescuing altered neuritic morphology around Aβ plaques [14]. Additionally, studies have shown that curcumin decreased Huntington protein aggregation [15], suppressed cell death relieving disease symptoms [16]; modulated accumulation of α-synuclein which is the prime reason for Parkinson's disease [17]. It has been reported that intravenous and oral administration of curcumin modulates dopamine related damage, induces microglial activation, and improves locomotion [18]. Curcumin has, further, shown to increase docosahexaenoic acid (DHA) levels [19]; improve learning and mental ability in

#### **Figure 1.** *Biological properties and chemical constituents of Turmeric.*

#### *Spices-Reservoir of Health Benefits DOI: http://dx.doi.org/10.5772/intechopen.96471*

scopolamine induced amnesia in mice [20]. Moreover, numerous other compounds with potent antioxidant activity have also been isolated from turmeric [21].

Curcumin has been known to downregulate production of inflammatory cytokines such as MCP- 1, TNF α, IL6, IL-1β both in vitro and in vivo [22–24]. However, recent study have suggested that efficacy to reduce levels of pro-inflammatory cytokines is enhanced on administering liposomal curcumin [25]. Studies have reported upregulation of heme oxygenase-1 reducing oxidative stress and providing protection against acute vascular inflammation in vitro as well as in vivo [26, 27].

Anti-rheumatic effects of curcumin have also been reported as curcumin decreased β3 and β7 integrins expression (adhesion molecules) ultimately decreasing joint inflammation; downregulated expression of chemokines, pro-inflammatory cytokines and growth-related oncogene/keratinocyte chemoattractant [28]. Further, randomized trials have also shown the efficacy of oral administration of curcumin in treatment of Rheumatoid Arthritis [29, 30].

Curcumin is effective in the management of virus infections as it inhibited Zika and Chikungunya virus at a concentration of 5 μM (IC50 = 1.9 and 3.89 μM respectively) [31], herpes simplex virus [32] and dengue virus [33]. Further, it inhibited human immunodeficiency virus (HIV) integrase and protease suggesting its protective effects against AIDS [34, 35]. The pandemic, COVID-19 related mortality is mainly due to acute respiratory distress syndrome with extensive cytokine storm. It has been reported that curcumin upregulates peroxisome proliferator-activated receptor-γ induction leading to inhibition of nuclear factor-κB (NFkb) signaling eventually decreasing cytokine storm [36] which suggests that curcumin might ameliorate COVID associated symptoms. Bioinformatic analysis have further shown ability of curcumin to interact with ACE2 receptor [37] and main protease [38] thereby fighting against COVID-19.

Curcumin displays antiparasitic and anti-cancer effects too. At a dose of 5 μM, it altered *P. falciparum* microtubules leading to reduction of 70–90% of parasitemia (IC50 = 50 μM) [39] and further at 100 mg/kg showed 80–90% decrease in *P. berghei* parasitemia [40]. Curcumin, in synergistic effect with Mitomycin C (5 μmol/L) arrested growth of MCF 7 breast cancer cell lines at G0/G1 phase of the cell cycle at a concentration of 40 μmol/L [41], decreased sensitivity of NFκB in human pancreatic cells lines BxPC-3, Capan-1, Capan-2, ASPC-1, and HS766-T (73–95% inhibition) [42], induced apoptosis [43]; inhibited cyclo-oxygenase 2 (COX 2- its overexpression leads to carcinogenesis) production in HT-29 colon cancer cell lines [44]. This prompts the requirement of detailed investigation to understand the potential of curcumin in cancer biology. Apart from curcumin, non-curcuminoids have also been reported to exhibit potential anticancer activities too [45].

Regardless of its demonstrated efficacy, purified curcumin has also been reported as pan assay interference compounds (PAINS) that show activity by interfering with assay readouts [46]. Curcumin exhibits PAIN properties such as fluorescence interference [47], aggregation [48], metal chelation [49], redox reactivity [50]. It is a highly unstable compound as it degrades rapidly in alkaline solutions [51]. Another drawback of curcumin is its poor bioavailability, however, number of formulations of curcumin with enhanced bioavailability and absorption are now available such as BioPerine-20x [52], BCM-95CG [52], Longvida-67x [53], Meriva-29x [54]. Furthermore, it is advised, traditionally, to consume turmeric powder with warm milk and ghee (Milk fat) as it is believed that this combination boosts immunity, purifies blood, beats everyday fatigue and anxiety, relieves cold and cough, which all are requirement to fight against COVID-19. Moreover, this combination might also enhance bioavailability of curcumin due to the constituents of milk and ghee such as casein, fats, iodine, phosphorus, calcium, vitamins etc.
