Mixing Propolis from Different Apiaries and Harvesting Years: Towards Propolis Standardization?

Abstract

Global demand for safe, effective and natural products has been increasing in parallel with consumers’ concerns about personal and environmental health. Propolis, a traditional and potentially medicinal product with several health benefits, is a beehive product with a worldwide reputation. However, despite the bioactivities reported, the low productivity and high chemical heterogeneity have been extensively hampering broader industrial uses. To assist in overcoming some of these problems, we prepared and characterized mixtures of ethanol extracts of a heterogeneous propolis sample (Pereiro) collected over a five-year period (2011–2015) and, additionally, we mixed two different propolis samples from distinct regions of Portugal (Pereiro and Gerês), also harvested at different times. An investigation of the antimicrobial and antioxidant properties, as well as characterization of the chemical composition of the eleven propolis blends were performed in this work. The antioxidant and antimicrobial activities of such blends of propolis samples, either from different localities and/or different years, were maintained, or even enhanced, when a comparison of the individual extracts was conducted. The differences in the chemical composition of the original propolis samples were also diluted in the mixtures. The results reemphasize the great potential of propolis and suggest that mixing different samples, regardless of provenance or harvesting date, can contribute to propolis standardization while simultaneously increasing its availability and adding value to this beehive byproduct.

An Insight on the Biomedical Potential of Portuguese Propolis from Gerês

“…Moreover, Peixoto et al [ 36 ] reported that blends of five ethanol extracts of propolis from Gerês collected over five different years are equally or even more interesting than the individual extracts, and a step towards standardization since combining less and more active extracts resulted in comparable bioactivities. Similar results were obtained later by the same team while combining ethanol extracts of propolis collected from different apiaries and harvesting years [ 37 ], which further highlights the usefulness of propolis blends to increase the availability and to value this beehive resource. Overall, these studies support the great potential of propolis mixtures and increase the interest and the valorization of this natural product.…”

“…This result revealed that mixing propolis retains the best antioxidant effect, which in turn might be related to the higher flavonoid content [ 28 ]. In comparison with the results previously reported for Gerês propolis mixtures extracted with absolute ethanol (mG.EE 100 ) (EC 50 values ranging from 11.8 to 13.7 µg/mL), mG.EE 70 presented a higher antioxidant capacity (EC 50 = 4.73 µg/mL), which can be related to the ethanol concentration used during the extraction process [ 36 , 37 ]. Not only the extraction solvent itself, but also its concentration may interfere with the chemical composition and, consequently, with the biological properties, e.g., the antioxidant potential, as has been reported [ 21 , 28 , 87 , 89 ].…”

“…It is a well-known fact that the Folin-Ciocalteu colorimetric assay generates higher polyphenol values in mixtures than in individual extracts [ 84 ]. Propolis blends can potentially minimize the variation observed within samples harvested in distinct years by attenuating the differences between individual samples and minimizing the heterogeneity, contributing to propolis normalization [ 37 ]. This evidenced potential of blends can be very useful for propolis applications in several areas, including the food sector and medicine.…”

“…Portuguese propolis is far from being completely characterized but results to date indicate that this natural product exhibits some biological properties, namely antimicrobial, mainly antibacterial, but also antifungal activities [ 35 , 36 , 37 , 38 , 39 ]; antioxidant potential [ 35 , 40 , 41 , 42 ]; as well as genotoxic [ 40 , 41 , 43 ] and antitumor [ 38 , 44 , 45 , 46 ] activities, renewing the interest in researching national propolis. More recently, Portuguese propolis samples from Gerês revealed constancy in biological and chemical profiles over the years [ 35 ], which seems to be a distinctive and particular feature of this kind of propolis.…”

Antimicrobial Natural Products

“…Propolis is a traditional, potentially medicinal product with several health benefits. Marta Peixoto and co-workers investigated the antimicrobial potential of ethanol extracts of propolis collected in Pereiro over a 5-year period (2011–2015) and two distinct apiaries/regions—Pereiro and Gerês—in selected years [ 2 ]. The results showed that a mixture of propolis and ethanol extracts had particularly interesting effects on Bacillus subtilis , Propionibacterium acnes , and Staphylococcus aureus .…”