BALTIMORE, Md. — Leafy greens are not only good for your health, they may help end the coronavirus pandemic as well. Researchers from Johns Hopkins Children’s Center have collected compelling evidence that a chemical found within broccoli and other cruciferous vegetables may offer a potent new way of fighting both COVID-19 and the common cold.

Scientists call the plant-derived chemical (phytochemical) in question sulforaphane. Prior work has already connected sulforaphane with cancer preventing benefits. Now, this latest work reports it can also inhibit the replication of SARS-CoV-2 (the virus responsible for COVID-19), and other coronaviruses across both cell and mice samples.

To be clear, while these results are very promising, study authors caution against running to the grocery store and cleaning out your local produce section. Additional studies focusing specifically on the impact of sulforaphane on humans are necessary before scientists can tell if the chemical is totally safe and effective.

The natural compound in leafy greens which turns into sulforaphane is especially abundant within broccoli, Brussels sprouts, kale, and cabbage. This compound was first discovered and identified as a “chemopreventive” by scientists at Johns Hopkins decades ago.

“When the COVID-19 pandemic started, our multidisciplinary research teams switched our investigations of other viruses and bacteria to focus on a potential treatment for what was then a challenging new virus for us,” says senior study author and Children’s Center microbiologist Lori Jones-Brando, Ph.D., an assistant professor of pediatrics at the Johns Hopkins University School of Medicine, in a media release. “I was screening multiple compounds for anti-coronavirus activity and decided to try sulforaphane since it has shown modest activity against other microbial agents that we study.”

Leafy greens even work against new COVID strains

The team notes people can derive natural sulforaphane from numerous common food sources, including broccoli seeds, sprouts, various mature plants, as well as sprout infusions or seeds for drinking. Meanwhile, it’s worth noting that additional work conducted by Johns Hopkins researchers suggests sulforaphane can help prevent cancer and infections by interfering with certain cellular processes. In the new study, every experiment used purified, synthetic sulforaphane acquired from commercial chemical suppliers.

Specifically, one experiment entailed exposing cells to sulforaphane for one or two hours before infecting the cells with SARS-CoV-2 and the common cold coronavirus HCoV-OC43. This process led to the observation that low micromolar (µM) concentrations of sulforaphane (2.4–31 µM) lowered virus replication by 50 percent among six distinct strains of SARS-CoV-2 — including the Delta and Omicron variants. Researchers discovered similar results among cells previously infected with the viruses. In these cases, the protective effects of sulforaphane were apparent even in reference to already established virus infections.

Pairing sulforaphane with a proven COVID treatment

Study authors also investigated the effect of mixing sulforaphane with remdesivir, an antiviral medication approved for use against COVID-19. This experiment resulted in remdesivir inhibiting 50 percent of the replication of HCoV-OC43 at 22 µM and SARS-CoV-2 at 4 µM, respectively. Furthermore, researchers believe sulforaphane and remdesivir interacted in a synergistic manner at several combination ratios to reduce the viral burden by 50 percent among cells infected with HCoV-OC43 or SARS-CoV-2.

For this research, synergism refers to particularly low doses of sulforaphane (1.6–3.2 µM) and remdesivir (0.5–3.2 µM) being more effective against a pathogen as a tandem as opposed to working alone.

“Historically, we have learned that the combination of multiple compounds in a treatment regimen is an ideal strategy to treat viral infections,” adds first study author Alvaro Ordonez, M.D., an assistant professor of pediatrics at the Johns Hopkins University School of Medicine. “The fact that sulforaphane and remdesivir work better combined than alone is very encouraging.”

The treatment works well in mice

From there, researchers conducted further tests using a mouse model of SARS-CoV-2 infection. That process led to the revelation that giving the animals 30 milligrams of sulforaphane per kilogram of body weight before infecting them with SARS-CoV-2 notably decreased the typical loss of body weight seen among infected rodents (7.5%).

This sulforaphane pretreatment also produced a statistically significant drop in the rodents’ viral loads within their lungs (17% decrease) and upper respiratory tracts (9% decrease). Lung injuries were also less frequent than the norm among COVID-infected mice not given any sulforaphane (29% decrease). Lung inflammation decreased as well, seemingly due to added cell protection against a “hyperactive immune response” that has been associated with many COVID-19 deaths.

“What we found is that sulforaphane is antiviral against HCoV-OC43 and SARS-CoV-2 coronaviruses while also helping control the immune response,” Dr. Ordonez says. “This multifunctional activity makes it an interesting compound to use against these viral infections, as well as those caused by other human coronaviruses.”

Moving forward, the research team is planning on conducting further sulforaphane studies with humans. The chemical may soon become a go-to option for preventing or treating COVID-19 cases and other viral infections.

“Despite the introduction of vaccines and other medications that can have side effects, effective antiviral agents are still necessary to prevent and treat COVID-19, particularly considering the potential effects of new coronavirus variants arising in the population,” Dr. Jones-Brando concludes. “Sulforaphane could be a promising treatment that is less expensive, safe and readily available commercially.”

The study is published in the journal Communications Biology.