**3.7 Effect on skin**

Due to its antioxidant properties, it has photoprotective properties. Unsaturated lipids make up a sizable portion of the lipids on the skin's surface. As a result, they are frequently targeted by free radicals. The sun's UV rays penetrate the epidermis, accelerating the oxidative damage produced by free radicals. Prolonged exposure to these radiations may damage the lipids, resulting in a loss of skin texture. Turmeric extract has been proven in laboratory experiments to reduce inflammation and protect epidermal cells from the damage caused by ultraviolet B radiation. Curcumin has been proven to protect against chromosomal damage caused by gamma radiation in tiny dosages of turmeric [38].

### **3.8 Anti-cancer effect**

Curcumin has been found to inhibit carcinogenesis via two distinct mechanisms: angiogenesis and cancer cell proliferation. Additionally, it inhibits cancer cell metastasis and promotes apoptosis in cancer cells [39]. Curcumin has been demonstrated to inhibit angiogenic factor stimulators such as VEGF and primary fibroblast growth factor. Indeed, curcumin has been shown to inhibit VEGF expression via NF-kB and AP-1 regulation, inhibiting IL-8 expression [40]. Curcumin is also capable of inducing apoptosis in cancer cells via a p53-dependent mechanism. p53 is a well-characterized tumor suppressor protein that regulates cell proliferation, necrosis, and DNA damage [41]. Curcumin has also been shown to reduce colon cancer by suppressing the Wnt/b-catenin signaling pathways via miR-130a [42]. In cancer models, curcumin has also been shown to inhibit and suppress the PI3K/Akt signaling pathway [43, 44].

### **3.9 Immunological activity**

Curcumin demonstrates a broad range of biological activities that benefit human health. Apart from these functions, curcumin's primary property is immunological activity, which is why it has been demonstrated to be effective against anti-immune diseases. When the effect of curcumin on the immunological profiles of the blood was explored, it was shown that white blood cells (WBCs) and especially lymphocytes produced increased levels of immunoglobulins (IgG and IgM) [45]. Curcumin has been shown to attenuate bradykinin-induced coughing [46, 47]. It inhibits chemokine release and, therefore, may protect against acute lung injury [46, 48]. Patients with severe respiratory sickness exhibit a hyper-immune response manifested by extensive alveolar destruction, epithelial apoptosis, fibrin accumulation, and the creation of a hyaline membrane. A low neutrophil to lymphocyte ratio is a poor prognostic predictor for COVID-19 at the cellular and molecular level [49, 50].

### **3.10 Antimicrobial properties**

The rhizome of *C. longa* has traditionally been employed as an antibacterial agent [51]. Numerous studies have demonstrated curcumin's antimicrobial activity, which includes antibacterial, antiviral, and antifungal properties:

### *3.10.1 Antibacterial activity*

Antibacterial activity against Staph. Epidermis ATCC 12228, Staph. aureus ATCC 25923, *Klebsiella pneumoniae* ATCC 10031, and *E. coli* ATCC 25922 were demonstrated using an aqueous extract of *C. longa* rhizome minimum inhibitory concentration values of 4–16 g/L and minimum bactericidal concentration values of 16–32 g/L [52]. Likewise, it was demonstrated that adding 0.3 percent (w/v) aqueous curcumin extract to cheese reduced *Salmonella typhimurium*, *Pseudomonas aeruginosa*, and *E. coli* 0157:H7 bacterial counts. Additionally, it reduced *Staph. Aureus, Bacillus cereus*, and *Listeria monocytogenes* contamination following a 14-day cold storage period [53]. Turmeric oil was also efficient against *B. subtilis*, *B. coagulans*, *B. cereus*, Staph. aureus, *E. coli*, and *P. aeruginosa* as a byproduct of curcumin synthesis [54].

#### *3.10.2 Antiviral activity*

Curcumin, a plant product, has been shown to exhibit a broad spectrum of antiviral action against various viruses. Due to its rate-limiting action in the de novo synthesis of guanine nucleotides, the inosine monophosphate dehydrogenase (IMPDH) enzyme has been proposed as a therapeutic target for antiviral and anticancer agents. Among the 15 specific polyphenols, curcumin has been recommended as a powerful antiviral agent via its inhibitory activity against IMPDH in either a non-competitive or competitive way [55]. Additionally, curcumin dramatically suppressed the acetylation of the HIV Tat protein by p300, which is related to the inhibition of HIV-1 replication. Curcumin is a potent chemical for combinatorial HIV treatments because it targets the p300/CREBbinding protein (CBP) acetyltransferase proteins [56].

### *3.10.3 Antifungal activity*

Historically, extracts from various natural resources, mainly plants, served as an effective armament for battling fungal infections and rotting. Curcumin inhibited the growth of two phytophagous fungi, *Fusarium solani and Helminthosporium oryzae*. Turmeric oil was highly effective against *F. solani* and *H. oryzae*, with an IC50 of 19.73 and 12.7 g/mL, respectively [57]. Turmeric powder was applied at concentrations of 0.8 and 1.0 g/L to plant tissue culture and showed a substantialinhibitory effect against fungal contaminations [58]. Curcumin also inhibited *Cryptococcus neoformans* and *Cryptococcus dubliniensis*, with a minimum inhibitory concentration (MIC) of 32 mg/L [59]. Curcumin was discovered to be a highly effective fungicide against 14 Candida strains, including four ATCC strains and ten clinical isolates, with MIC values ranging from 250 to 2000 g/mL [60].
