Propolis extract shows antiviral activity against Zika, Chikungunya and Mayaro

Research conducted at the Butantan Institute seeks to identify a compound that can be used in both the prevention and treatment of arboviruses.

By Fernanda Bassette  |  Agência FAPESP – Research carried out by scientists from the Butantan Institute in the city of São Paulo (Brazil) has shown that an aqueous extract of propolis is capable of combating the replication of the Zika, Chikungunya and Mayaro viruses. The three pathogens are transmitted by the bite of mosquitoes that circulate in Brazil and cause infectious diseases (arboviruses) for which there is still no vaccine or specific treatment available, motivating the search for compounds with antiviral potential. The extract was tested in vitro and significantly reduced the viral load of the three viruses.

The study was carried out at the Center for Research on Toxins, Immune Response and Cell Signaling (CeTICS), one of the Research, Innovation and Dissemination Centers (RIDC) supported by FAPESP, under the direction of researchers Pedro Ismael Silva Júnior, from the Laboratory for Applied Toxinology, and Ronaldo Mendonça, from the Butantan’s Laboratory of Parasitology. The results were published in the journal Scientific Reports.

This is not the first time that the group has studied the antiviral and antibacterial potential of propolis. The team’s previous study, carried out with a hydroalcoholic extract of the substance, had already indicated intense activity against the herpes, influenza and rubella viruses. Based on the initial results, the scientists decided to evaluate whether the aqueous extract would have the same activity on other types of viruses that are also important from a public health point of view in the country.

Extract preparation and analysis

To obtain the results, the group used propolis produced by native stingless bee Scaptotrigona aff. postica, originating from a colony in the region of Barra do Corda, in Maranhão, a state in the northeast of Brazil. The propolis was obtained by scraping the meliponiculture box, forming a kind of paste. This material was transported and frozen at -20 °C, forming a frozen propolis stone.

This stone was manually macerated until it became a granular material that was passed through sieves. The product was then ground into an even finer compound, which was again passed through sieves and turned into a powder. Finally, the researchers added ultra-purified water to the powder, and the material was centrifuged for 30 minutes to separate the wax from the liquid medium. The supernatant (the liquid phase on top) was filtered and the product was considered 100% purified.

(image: researchers’ collection)

In order to determine the antiviral activity of the propolis extract, the researchers infected VERO cells (a strain derived from monkey kidneys and often used in this type of study) cultured at 37 °C in microplates. The team monitored the growth and morphology of these cells on a daily basis. “We contaminated the cultures with the three viruses of interest and added the substance we wanted to analyze only once, at a level of 10% of the volume. From then on, we made serial dilutions, in other words, we reduced the amount of this solution to see how much would stop the virus from multiplying,” explained Silva Júnior.

The researchers observed that the purified aqueous propolis extract promoted a 16-fold reduction in the viral load of the Zika virus and a 32-fold reduction in that of the Mayaro virus. In the case of Chikungunya, the reduction was even more significant, 512 times.

Further research

For the time being, the results obtained are limited to the laboratory environment, but the research continues. In a second phase of the work, the group collected propolis month by month, in order to associate the final product with the flowering of each period. This is because the Scaptotrigona aff. postica bee uses plants from the Maranhão region, which are different from those found in São Paulo, located in the southeast of Brazil, and so the propolis obtained probably has specific components related to the species endemic to the area.

“We’ve already observed that there are differences throughout the year. Now we want to identify when the substance with antiviral activity appears, because we want to associate it with the plant that the bee uses to produce propolis,” Silva Júnior explained.

It is important to note that the propolis in the study is different from the commercial propolis found in pharmacies. The product sold to consumers is usually an alcoholic extract that mixes all the components of propolis, and in most cases comes from the species Apis mellifera (European bee), which is the dominant bee in apiaries. The propolis used in this research comes from the native Brazilian bee Scaptotrigona aff. postica, and the compounds with antiviral activity are separated, purified and isolated.

Bioactive compounds

The search for potential medicines in nature – the famous bioactive compounds – is one of the great focuses of science. Brazil has a very large area with extremely diverse flora and fauna, and the use of substances from its forests is very important, both scientifically and economically, as it can reduce the cost of the final product.

The researcher emphasizes that the goal of the research is to try to identify a compound that can be used both to prevent and to treat people infected with the virus. “We don’t yet have the elements to reach that point, but the idea is to achieve both objectives,” Silva Júnior said.

But there is still a long way to go. “If we’re thinking of creating a potential drug, many more studies need to be done. This is a very important discovery, but the results were obtained in vitro. In vivo research with mice and guinea pigs is still needed to confirm the antiviral effect, and only then can research be carried out in humans,” he concluded.

The article “Antiviral action of aqueous extracts of propolis from Scaptotrigona aff. postica (Hymenoptera; Apidae) against Zika, Chikungunya, and Mayaro virus” can be read at: www.nature.com/articles/s41598-024-65636-7.