Curcumin as an Antiviral Compound

Before we get into the therapeutic & antiviral effects of turmeric against viruses and viral infections let’s first talk about “What is a Virus?”, “What causes viral infection?” and “How to fight against viral infections?”.

Viruses are like tiny parasites containing genetic materials like DNA & RNA and can cause diseases as minor as cold or as major as HIV-AIDS. Since viruses contain genetic material they can reproduce themselves into the host cells and infect them, but they are metabolically immobile when outside the host body.

Our body has its own natural resistant mechanism(immune response) against viral infections, namely – Humoral Immunity & Cell Mediated Immunity. Humoral Immunity is for when the virus is present in the humors or body fluids. Cell Mediated Immunity does not involve antibodies and is associated with immunization of cells.

Due to the lack of preventive and therapeutic options for many viral infections, numerous studies have been conducted to investigate the antiviral potential of natural compounds. For curcumin, an antiviral activity was observed against several different viruses including hepatitis viruses, influenza viruses and emerging arboviruses like the Zika virus (ZIKV) or chikungunya virus (CHIKV).

Interestingly, it has also been reported that the molecule inhibits human immunodeficiency virus (HIV), herpes simplex virus 2 (HSV-2) and human papillomavirus (HPV), indicating that curcumin reduces the spread of sexually transmitted diseases.  
 

Curcumin Inhibits Influenza A Virus

Influenza viruses belong to the family Orthomyxoviridae and can be divided into three types: A, B, and C. The influenza A virus (IAV) mainly infects birds, but it can cause severe pandemics in domestic poultry and in humans, even though this happens rarely.

• Several studies tested the effect of curcumin on different IAV types in vitro and found it to inhibit virus uptake, replication and particle production. Experimental work and structure-relationship modeling suggested that the inhibition was due to the molecule interfering with binding of the viral glycoprotein hemagglutinin (HA) to its cellular receptor.
• A subsequent study confirmed this effect and explained it by curcumin’s ability to modulate the features of lipid bilayers. The compound alone was as effective in dampening IAV infection as pure curcumin and a synergistic effect of the two analogs was observed.

Curcumin Inhibits Herpes viruses (Herpes simplex Virus) HSV

The most famous herpes virus is probably the herpes simplex virus, which is categorized into two types: HSV-1, commonly associated with orofacial ulcer and HSV-2, which mainly causes genital ulcers.

• Several studies found that low micro molar, not cytotoxic amounts of curcumin dampened HSV-1 and HSV-2 infectivity. For HSV-1 this is associated with a considerably decreased expression of viral immediate early (IE) genes, which is due to a reduced RNA polymerase II recruitment to IE gene promoters.
• Intriguingly, similar to HIV, the pretreatment of human genital epithelial cells with the curcumin reduced the shedding of HSV-2 from these cells, a mechanism that might help to stop the spread of the sexually transmitted disease. Another highly prevalent Herpesviridae member is the human cytomegalovirus (HCMV).

Curcumin Inhibits Human Papilloma virus (HPV)

Human papillomaviruses cause persistent cutaneous or mucosal infections, and the infection with at least 13 HPV types is associated with the development of multiple types of cancer. Especially the cervical cancer, the fourth-most common cancer in women, is tightly linked to HPV infection and in over 60% of the cases the high-risk HPV types 16 and 18 are detected.

• The effect of curcumin on HPV infection and HPV-associated tumor growth has been extensively studied. Already in 1990 the group of scientists could show that the viral oncoprotein E6 of HPV-16 and 18 complexes with the tumor suppressor protein p53, targeting it for proteasomal degradation.
• In silico modeling suggested that curcumin binds to the p53 interaction site of E6, by prohibiting it from binding p53. In addition, in vitro studies showed that curcumin inhibited E6 and E7 expression and by this rescued p53 levels.

Ginger combats human respiratory syncytial virus (RSV)

Human respiratory syncytial virus (RSV) is one of the most common contagious virus infections that occur in children. Symptoms include fever, stuffy nose wheezing and runny nose. Many RSV illnesses are confused with the common cold. However a bout of RSV will typically last for longer, and will typically include wheezing. In younger children this can turn fatal

The inhibition of the virus occurred more readily among the alveolar (lung) cells – illustrating the potential for the ginger to inhibit RSV infections of the lungs.

Curcumin Inhibits Arboviruses

The group of arboviruses comprises different viruses which are transmitted by arthropod vectors like ticks and mosquitos. Nowadays arboviruses are rapidly re-emerging worldwide, as arthropod habitats are expanding due to climate change and the increase of global traffic.

For most arboviruses, except Japanese encephalitis virus and yellow fever virus (Flaviviridae), no vaccines are available and there is a lack of specific preventing or curing treatment for all of them.

• Recently, two studies revealed that curcumin blocks the entry of CHIKV (Tongaviridae) by inhibiting its binding to host cells. Incubation of cells with the natural compound also significantly dampened infection with Dengue virus, JEV and ZIKV (Flaviviridae) via the same mechanism. Similar as for HCV and IAV, this might be due to curcumin’s influence on membrane properties.
• In addition to inhibiting virus entry, curcumin treatment of cells already infected with DENV or JEV resulted in the intracellular accumulation of viral proteins and a reduction of viral particle production. Also Rift Valley fever virus (RVFV; Phenuiviridae) has been shown to be inhibited by curcumin: scientists observed that the molecule inhibits IKK-mediated phosphorylation of the viral NSs protein, resulting in reduced viral replication.

SUMMARY

• Turmeric is ancient Ayurvedic medicine. Its anti-inflammatory, anti-viral, anti-oxidant, anti-tumor, antibacterial, anti-fungal activities are responsible for its extensive use in the healthcare industry.
• All these important medicinal properties of turmeric are because of its primary polyphenolic compound Curcumin obtained from its roots.
• Despite the body’s immune responses against viral infections, they are still easily contracted and are difficult to treat.
• Most often, the virus cannot be destroyed once a viral disease is contracted.
• The symptoms of viral infections are difficult to detect in the early stages and this usually worsens the conditions.
• Curcumin has been found effective against a number of life- threatening viral infections like HIV- AIDS, Herpes, Influenza, Hepatitis, Ebola, Human Papillomavirus and Rift Valley Fever Virus, etc.
• It produces anti-viral activity by inhibiting the interaction of viral proteins with cellular receptors on host cells.