Propolis has proved to be a product with ability to have beneficial effects for health

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Propolis (Pro-before, Polis-city = defence of the city), is the resinous substance that bees gather from the leaf buds of trees and certain vegetables. The bee gathers this and transforms it in order to disinfect the beehive, seal cracks, build panels, as well as using it as a microbiocidal agent, disinfectant and also for embalming intruders otherwise difficult to expel due to their size. Propolis is, thus, directly responsible for guaranteeing the asepsis of the beehives, locations prone to developing viruses and bacteria, given their conditions of temperature and humidity.

Although the precise composition of propolis depends on the zone of beehive activity (climate, surrounding vegetation, and so on), as a rough guide, we can mention the following: resins and balsams (50-60%), waxes (20-25%), essential oils (5-10%), pollen (5%), others (minerals, enzymes, etc. 5%).

The fraction of resins and balsams is the one that contains most of the biologically active compounds, mainly phenolic ones derived from the vegetable kingdom and having proven pharmacological abilities. Due to the great number of active ingredients present, tincture (alcoholic extract) of propolis is well-known and used for its therapeutic properties, principally for its stimulant action on the organism's defence system. Notable amongst its properties are its antioxidant and anti-microbial action, its activity as a stimulant and its healing, analgesic, anaesthetic and anti-inflammatory activity.

The study of the biological activity of this product was undertaken following two lines of work: (a) a study of the antioxidant activity and (b) a study of the anti-microbial action.

Antioxidant properties

The antioxidant activity trials provided knowledge about the capacity of the product under study (propolis) for neutralising free radicals. These radicals represent damaged molecules, generated both in endogenous and exogenous ways, capable of causing damage at cell level, and causing the onset of future degenerative illnesses, such as cancer, Alzeheimer, and so on.

A diet rich in antioxidants minimises the risk of the onset of this kind of illness, and so the evaluation of the antioxidant activity of a product when establishing its preventative potential is of great interest.

This type of trial involves the artificial generation of free radicals in the laboratory and which are subsequently made to react with the sample to which the antioxidant properties are attributed, in order to estimate their capacity for neutralisation. To this end, three spectrophotometric techniques were applied.

Antimicrobial properties

The test for anti-microbial action enables the evaluation of the inhibition exercised on the growth of certain microorganisms by the product under study. The MIC (Minimum Inhibitory Concentration) methodology involved the diffusion of the substance under study in a medium in which the growth of the microorganisms is optimum. If the substance diffused has a capacity to impede the growth of the chosen microorganism, a halo will appear around the central point where the product has been deposited. Otherwise, the medium will remain unaltered.

To carry out this trial the strains were activated in an optimum medium containing the necessary nutrients for the growth/development of the microorganism. When growth reached the Macfarlane index, close to 0.5, agar was added and seeded in rectangular plaques. Once solidified, the plaques were drilled and, by means of templates, various concentrations of propolis (0.1-50%) were deposited. All the concentrations were tested in triplicate. The plaques were incubated at 37 °C and, after this, the presence/absence of the halos of inhibition was detected and which provided a visualised measurement of the inhibition exercised by the propolis on the growth of the microorganism used. These halos of inhibition were measured with calibres and the values obtained were extrapolated using as a template a plaque seeded with various concentrations of phenol (1-10%), which has a powerful biocide activity.

The MIC trials were undertaken with the following microorganisms:

* Streptococcus mutans (dental caries)
* Candida albicans (vaginal infections)
* Salmonella tiphy (salmonellosis)
* Helicobacter pylori (stomach ulcer)
* Saccharomyces cerevisiae (opportunistic role in asepsis of Aids sufferers, leukemia-)

The microorganisms selected were bacteria, yeasts and fungi responsible for common and very heterogeneous complaints.

Antioxidant capacity

The antioxidant activity trials were carried out dissolving propolis in two types of solvent: 70% ethanol and propylenglycol.

The results coincided with what was expected, as this product has a high quantity of biologically active components, outstanding amongst these being the flavonoids (known for their high antioxidant power). The flavonoids are in fact most responsible for all the medicinal properties attributable to propolis: antibacterial, antimycotic, antifungal, antiviral, antitubercular, cytostatic, antiallergic, antioxidant, antitoxic, hypotensor, haemostatic, immunogenetic and antiparasitical.

The prepared ethanol extracts showed a high inhibition of the radicals employed. The values were within the established ranges. Although there were significant differences between them, these may have been due to the location of the hives as well as the degree of impurities present in the same.

As can be seen from the results, there were small differences between the different extracts (ethanol and propylenglycol), although these were not significant. The values fluctuate and, in the case of propylenglycol, they were less, but this variation did not appear to affect the composition of the final product in any drastic manner.

To date, in the literature consulted, no antioxidant capacity values have been found greater than those obtained for propolis, for any of the products/foods analysed, using this type of methodology.

Antimicrobial capacity

The development and growth of all these microorganisms studied were seen to be inhibited in the presence of different concentrations of propolis. The minimum inhibitory concentrations were produced at very low concentrations of the product, thus corroborating the high antimicrobial potential of the product. These results show that propolis is made up of compounds with high antimicrobiological activity, probably derived from its high content of phenolic, flavonoid compounds - originating from the vegetable kingdom.

Elhuyar Fundazioa