Growing concerns about health has caused the scientific community to focus their interest on investigating functional foods which contribute to boosting the prevention and reduction of the risk of suffering from certain illnesses. The benefits of this product lies in its composition and, thus, its study, identification and subsequent extraction provides a useful tool which enables making high added-value products, given their high concentration of biologically active compounds.
Over the past 5 years, Neiker-Tecnalia, in collaboration with the Fundación Kalitatea, apicultural associations in the Autonomous Community of the Basque Country, honey producing plants and Basque governmental bodies, has undertaken R+D projects associated with the beekeeping sector. Various products derived from the beehive have been studied and propolis has proved to be a product having beneficial results for human health.
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.
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.
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 ºC 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.