A new study reviews the potential for curcumin and nanosystems to treat COVID-19. Curcumin has been characterized and studied thoroughly, as a natural molecule with medicinal properties. Its tolerability and safety have been well documented, with a maximum dose of 12 g/day. Curcumin inhibits viral enzymes due to its ability to inhibit the virus itself, as well as to modulate inflammatory pathways.
It regulates viral transcription and regulation, binds with high potency to the viral main protease (Mpro) enzyme that is key to replication, and inhibits viral attachment and entry into the host cell. It may also disrupt viral structures. It has been reported to inhibit the 3C-like protease (3CLpro) more effectively than other natural products, including quercetin, or drugs like chloroquine and hydroxychloroquine. It also inhibits papain-like protease (PLpro) with a 50% inhibitory concentration (IC50) of 5.7 µM that surpasses quercetin and other natural products. Modeling studies have shown that curcumin inhibits this virus-receptor interaction in two ways, by inhibiting both the spike protein and the ACE2 receptor. Nanostructured carries can be used to deliver curcumin as it has low bioavailability when administered orally and undergoes rapid metabolism by the gut and the liver.
Three or more nanostructure-based curcumin products are already commercially available, but few studies have examined their efficacy against COVID-19 in vivo. These showed the ability of the formulations to modulate immune responses and to reduce the symptoms of the disease, and perhaps hasten recovery. Earlier studies show that silver NPs loaded with curcumin led to increased antiviral activity compared to either curcumin or silver NPs in isolation, with reduction of cell-cell fusion and syncytium formation.
Curcumin-carbon dots are another option found to be effective in inhibiting entry by the porcine epidemic diarrhea virus, again a coronavirus. These findings indicate the potential for the investigation of both curcumin and nanosystems for the treatment of SARS-CoV-2. Further studies are needed to validate the anti-SARS-CoV-2 activity of both these molecules.