Potential use of turmeric in COVID-19.

Turmeric (Curcuma longa L.) is a spice that is an integral part of Asian cooking and culture, and has been used in traditional medicine systems such as Ayurveda, Unani and Siddha for centuries, owing to its wide array of medicinal properties. Curcumin, the predominant curcumoid in turmeric, influences multiple signalling pathways and been found to possess anti‐inflammatory, antioxidant, antimicrobial, hypoglycaemic, wound‐healing, chemopreventive, chemosensitizing and radiosensitizing properties. To enhance the bioavailability of curcumin, newer technologies such as adjuvant, nanoparticles, liposomes, micelles and phospholipid complexes have been evaluated in the process of drug development. It is documented to be most efficacious in high doses at approximately 6–7 g/day orally, which is well tolerated. It has been widely used as a common household remedy for cough, sore throat and respiratory ailments in Asia.

Since December 2019, coronavirus disease 2019 (COVID‐19), caused by severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) virus, has spread rapidly throughout the world and the World Health Organization (WHO) declared it a global pandemic on 11 March 2020. As of May 2020, more than 212 countries across the world had reported over 4 million cases and over 280 000 deaths. So far, no specific medicine has been recommended for its cure or prevention, although antiretroviral drugs and hydroxychloroquine have been used in a few centres.

Numerous curcumin derivatives have been evidenced to have antiviral properties. Studies using neuraminidase activation assay showed that five active curcumin derivatives decreased H1N1‐induced neuraminidase activation in H1N1‐infected lung epithelial cells. Tetramethylcurcumin and curcumin even downregulates nucleoprotein expression., Various researchers have found turmeric derivatives useful in the management of influenza virus infections. Richart et al. observed that monoacetylcurcumin and curcumin both inhibited influenza virus infection, but via different pathways. Significant antiviral activity of turmeric against H5N1 (highly pathogenic avian influenza) virus in Madin–Darby canine kidney (MDCK) cells in vitro by interfering with viral haemagglutination (HA) activity has also been observed. The effects of anti‐H5N1 virus activity by turmeric extracts were demonstrated by upregulation in the tested MDCK cells of the mRNA expression of the genes for tumour necrosis factor‐α and interferon‐β, which are potent antiviral agents. Curcumin has been found to be beneficial in other viral disorders such as AIDS due to its inhibitory activity against HIV protease and integrase along with its synergistic action on other therapeutic drugs. It has also been shown to inhibit other viruses such as hepatitis B, hepatitis C, zika, chikungunya and dengue. Respiratory distress syndrome with fulminant hypercytokinaemia and multiorgan failure is the leading cause of mortality with COVID‐19. Curcumin has been found to attenuate influenza A virus‐induced lung tissue injury by blocking nuclear factor κB signalling and inhibiting the production of inflammatory cytokines. Curcumin is a natural ligand of peroxisome proliferator‐activated receptor‐γ, which represses the inflammatory process by reducing cytokine production; therefore, it might play a similar role in protecting against lung injury associated with COVID.

Turmeric has been used for centuries with a good safety profile. It has shown promising efficacy against influenza A viral infections by regulating the immune response to prevent injury to pulmonary tissue. Well‐defined randomized studies should be performed to evaluate the efficacy of turmeric derivatives against SARS‐CoV‐2 and assess its value as a possible treatment for this deadly virus.

Conflict of interest

The authors declare that they have no conflicts of interest.