Anti-Viral Compounds in Neem

 In Rumors We Hear

From the common cold and flu that sweep through neighborhoods every winter to West Nile, Dengue and Ebola, viral infections are among the most challenging facing researchers around the world. Unlike bacteria, which is a living cell, a virus is just a fragment of DNA in a protective coat. When it comes in contact with a cell, it can inject its DNA into the cell, which then reproduces new virus particles.

That makes it difficult to kill a virus, and even the most modern antiviral drugs do not destroy the infected cells. Instead they inhibit reproduction rates of the virus to minimize its spread.


Neem brings a potent one-two punch as a potential antiviral agent. First, and perhaps most importantly — as in how soon will I feel better? — neem boosts your body’s immune system, kicking your cell-mediated immune system into overdrive. Killer-T cells destroy microbes, viruses and cancer cells by injecting toxic chemicals into the invaders.

While researchers still have not pinpointed how neem works as an antiviral agent, it appears to make it difficult for the virus to reproduce, thus minimizing the impact of an infection. Over the past 50 years, researchers have shown that neem inhibits the growth of many viruses, including polio, HIV, coxackie B group, and dengue in the early stages of their replication.

Most recently a study published in the peer-reviewed BMC Complementary Medicine and Therapy used a technique called molecular docking to identify compounds that provide “universal” protection against influenza. While several synthetic compounds are effective against the various strains of the flu, no single agent addresses the multiple variations in the virus — one of the reasons it’s so difficult to control them.

They looked at three compounds in neem (nimbalflavone, rutin and hyperoside) against an influenza virus nucleoprotein, and then compared their action against six other drugs known to inhibit the growth of viruses. Hyperoside from neem leaf extract compared favorably with the synthetic compounds. More importantly, hyperoside worked against all strains of influenza rather than specific variations impacted by the synthetic drug. (Learn more here.)

First Reports on Anti-Viral Compounds Date to 1969

One of the first modern reports of neem being used as a medicinal herb focuses on the use of a neem leaf extract as an effective antiviral. It was published in 1969 by the Indian Journal of Medical Research. A series of reports after that documented that neem extracts significantly inhibited the polio virus, HIV, coxackie B group virus, and dengue virus at an early stage of viral genome replication (Badam et al., 1999; Parida et al., 2002; Rai and Sethi, 1972, Rao et al., 1969, Reddy and Sethi, 1974; Upadhyay et al., 1993; Sai Ram et al., 2000). However, they were all pre-Internet and links aren’t readily available.

Nearly 20 years later, researchers at Johns Hopkins University published a report in the journal Contraception showing that neem “provided significant protection” against the herpes simplex virus-2 in mice infected with the highly infectious virus.

A second study on herpes, published in Phytotherapy Research in 2010, focused on the role of neem bark as an entry inhibitor on the HSV-1 strain of herpes. Pretreatment of target cells most likely to become infected significantly blocked the virus from entering. The researchers took their work a step further and tested the ability of neem to block different and more virulent strains of the virus. Again, neem bark extract blocked entrance even on the more virulent strains.

That was followed by a 2002 study published in the Journal of Ethnopharmacology reporting that neem leaf extract inhibits the growth of Dengue virus, type 2, a viral hemorrhagic fever related to Ebola. The study used water extracts of neem at maximum non-toxic concentrations. In vitro (test tube) tests showed it completely inhibited the virus. In vivo tests conducted on mice showed the neem extract resulted in inhibition of the virus as confirmed by the absence of symptoms.

Another report published in the Journal of Communicable Diseases indicates that neem leaf extract inactivated and interfered with the reproduction of the coxsackie B virus in test tubes. One of a group of enteroviruses that are second only to the “common cold” as the most infectious viral agents in humans, the enteroviruses cause an estimated 10 to 15 million or more infections a year, including respiratory, neurological and muscular diseases.

In the study, neem leaf extract inhibited plaque formation in six types of the Coxsackie virus at concentrations of 1000 micrograms per milliliter. The reports note that the neem leaf extract was most effective as a viricidal agent, and also interfered with the virus’s reproductive cycle at an early stage. Additionally, researchers say the evidence suggests that the entire “battery” of compounds in neem have antiviral action for the coxsackie B group of viruses.

Anti-Viral Compounds Focus of Ongoing Research

Much of the research over the years has been done in India and Pakistan where neem is traditionally used as an antiviral agent and researchers are working to document its efficacy. The Indian Journal of Experimental Biology has reported that neem “significantly enhanced” antibodies against the Newcastle Disease virus – a highly contagious and generally fatal disease affecting all species of birds.

One of the few human studies on neem as an antiviral agent was partially funded through an agency of the US government in Nigeria in 2007. Sixty AIDS patients given neem leaf extract for 30 days gained an average of three kilograms – more than 6.5 pounds – plus saw significant increases in key parameters including CD4+, hemoglobin and platelet counts. The researchers also found that neem leaf extract protected 75% of human cells in a test tube from the HIV virus.

We’ll continue to monitor research specifically related to viruses, but you may want to check out how it boosts immune systems. Here’s a link to the National Institutes of Health; we’ll “translate” those reports over the next few weeks and post them in a new blog.

And while this post focuses on neem’s antiviral compounds, its antibacterial activity comes in really handy this time of year. It’s typically challenging to tell the difference between an infection and the flu. Most of the current research focuses on its use in preventing gum disease. Here’s a link to the National Institutes of Health on its antibiotic properties.

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