Study demonstrates antioxidant and antimicrobial activities of organic Brazilian propolis

Research investigated 78 samples collected in various apiaries in the states of Paraná and Santa Catarina.

By José Tadeu Arantes

Agência FAPESP – Brazil is the world’s second largest producer of propolis, surpassed only by China. Of the 700 to 800 tons of propolis consumed annually in the world, Brazil accounts for 150 to 170 tons, meeting the needs of 80% of the Japanese market, among others. However, the number of Brazilian patents for the product is still extremely low. Indeed, it is estimated that more than 43% of the world’s patents on Brazilian propolis have been deposited by Japanese institutions or companies.

The European market is currently showing a strong interest in certified organic propolis produced in Brazil because the product is free of heavy metals and microbial contaminants and offers a distinctive, delicate taste. To date, however, there have been no studies carried out that attest to the fact that this propolis is able to meet the expectations of consumers who seek the product for its potential antioxidant, antimicrobial, anti-inflammatory, anticariogenic and even anticarcinogenic properties.

A study that confirmed the antioxidant and antimicrobial properties of certified organic propolis produced in the southern region of Brazil was recently completed by agronomist Severino Matias de Alencar, associate professor of the Luiz de Queiroz College of Agriculture (Esalq) of the University of São Paulo (USP), with support from FAPESP.

In collaboration with pharmacist Pedro Luiz Rosalen, full professor of Pharmacology, Anesthesiology and Therapeutics at the Piracicaba Dental School (FOP) of the University of Campinas (Unicamp), and with participation by doctoral candidate Ana Paula Tiveron (Esalq) and post-doctoral fellow Bruno Bueno Silva (Institute of Biomedical Sciences, USP), both recipients of FAPESP scholarships, Alencar analyzed 78 samples collected from different apiaries in the south of Paraná and north of Santa Catarina.

In all, seven varieties of organic propolis were identified to have antioxidant activities (as assessed using sequestration techniques for superoxide radicals, peroxide radicals and hypochlorous acid radicals) and antimicrobial activities (with regard to the bacteria Streptococcus mutans, Streptococcus sobrinus, Staphylococcus aureus, Streptococcus oralis and Pseudomonas aeruginosa).

“This determination was significant because there was some doubt with regard to this organic propolis due to the very low levels of flavonoids, which are substances known to be responsible for the antioxidant and antimicrobial properties of propolis, especially in temperate climates. However, we verified that these same properties are also demonstrated by phenolic acids,” Alencar told Agência FAPESP. “In the varieties studied, we determined high levels of gallic, caffeic and coumaric acids, among other types of phenolic acids.”

Phenolic acids and flavonoids belong to the same chemical class, phenolic compounds, the principal feature of which is the presence of at least one hydroxyl radical bonded to a benzene ring as its molecule.

“The antioxidant activity arises from the donation of hydrogen electrons or ions (H+) originating from the hydroxyl, which reduces oxidant free radicals. The antimicrobial activity arises from one of the three following modes of action: (1) reaction with the cell membrane, altering its permeability and causing the loss of cell constituents or structural changes in the membrane’s fatty acids; (2) inactivation of enzyme systems or essential enzymes such as H+-ATPase or (3) supra- or infra-regulation, involving stress adaptation genes, glucose and other factors,” Alencar and Rosalen explained.

Protective activity

The antimicrobial activity of propolis was already empirically known by ancient Egyptian priests, who used it in the embalming process to protect mummies from fungi and bacteria. It is reported that propolis was also used in the Middle Ages to prevent infections in the umbilical cords of newborns. Furthermore, even up to the Second World War, propolis was used as a healing agent and antimicrobial in treating soldiers in some hospitals in the former Soviet Union.

The product basically consists of a resin exuded by plants and collected from the buds of flowers by bees found in a given biome. The bees gather up the resin and carry it to the hive where it performs a series of useful functions, such as sealing, waterproofing and environmental asepsis. These essential functions for hive preservation were what led this material to being called “propolis” (from the Greek pro, “to the benefit of” and polis, “city”).

“Many plants secrete resins to protect their growing buds and leaves. Due to its constitution, which is rich in phenolic compounds, these resins have extensive antioxidant, antifungal and antibacterial abilities. The bees scrape the plants and carry off the resins,” Alencar explained.

“Once back at the hive, the function of propolis is above all physical protection because the bees do not like light and use the resin to seal cracks and create a shadowy, thermally insolated environment. As a result of its antimicrobial action, the material also works as a powerful sterilizer, causing the air inside the hive to be more sterile than the air outside.”

The producers remove the propolis by creating side openings, two to three centimeters high, in the resinous covering of the hive – openings that are then closed again by the bees with more resin.

“The samples we collected were produced in reforested areas or areas of native forest. This gives the production of organic propolis additional merit in that it acts to preserve the environment, which is indispensable to the success of this undertaking,” the researcher affirmed.

“Doctoral candidate Ana Paulo Tiveron is currently using semi-preparative HPLC techniques and mass spectrometry to analyze the bioactive compounds responsible for the antioxidant activity. We hope that by identifying these biologically active compounds, we will be able to obtain chemical markers for propolis,” Alencar said.

“Our work is well underway, and we will soon be filing patents associated with organic propolis, thereby safeguarding Brazil’s intellectual property,” he added.

The next step, already planned by Alencar and Rosalen, will be to study the potential anti-inflammatory and anti-nociceptive (analgesic) activity, cytotoxicity and anti-proliferative (anticancer) action of organic propolis.

In addition to this, the researchers are planning to study the possible differences between aqueous and alcoholic solutions of propolis. The research conducted thus far has been carried out using the alcohol solution, which is easier to produce. However, as many consumers cannot or do not wish to ingest alcohol, there is a growing demand for an aqueous extract. “The company that makes the product in the region of União da Vitória, in Paraná State, is very interested in supplying this market segment and has asked us for a study about it,” Alencar said.