Table 5.

Mechanism of action of curcumin on virus replication process

Process	Mechanism of action	Reference
Viral attachment/penetration	Curcumin could alter the surface protein structure in viruses and block the entry of viruses to the cell. In addition, the positively charged curcumin on the surface is subjected to electrostatic interactions with porcine epidemic diarrhea virus (PEDV) or cell membranes and competing with the virus to bind with the cells. A molecular ducking study indicated that curcumin possesses the better binding capability to the receptors and may inhibit the entry of COVID‐19 virus.	75
Viral replication	The effects of curcumin on negative‐strand RNA synthesis by using PEDV as a coronavirus model. They demonstrated that curcumin could inhibit PEDV at the replication step. This evidence supports the potential role of curcumin as a promising antiviral agent. The effect of curcumin on viral replication, by quantification of the number of spike proteins present in cultures of Vero E6 cells infected with SARS‐CoV. Their result demonstrated that the inhibitory effect of curcumin in half maximal concentration (EC50) values was higher than 10 μmol L−1 on SARS‐CoV replication.	75,76
Potential inhibitory effect of curcumin on viral protease	The drugs that are at present tried for the management of COVID‐19 are protease inhibitors that primarily act on the main protease curcumin that may have the potential to inhibit the COVID‐19 infection by molecular docking. Curcumin showed relatively low binding energies and inhibition constants. They suggested that curcumin could have a potential inhibitory effect on COVID‐19 and could potentially act as a therapeutic agent.	77
Potential effect of curcumin on interferons	Interferons play an essential role in the defense against coronavirus infection. These viruses could hinder the induction of interferon in humans. All types of interferons play a role in preventing viral infections. Treatment with cationic carbon dots based on curcumin can suppress PEDV model of coronavirus reproduction by stimulating the production of interferon‐stimulating genes (ISGs) and the cytokines (IL8 and IL6) of Vero cells by triggering the innate immunity of the host.	78