Propolis Efficacy: The Quest for Eco-Friendly Solvents

Abstract

Propolis, a natural product made by bees with resins and balsams, is known for its complex chemical composition and remarkable bioactivities. In this study, propolis extraction was studied seeking extracts with strong bioactivities using less orthodox solvents, with some derived from apiary products. For that, a propolis sample collected from Gerês apiary in 2018 (G18) was extracted by maceration with six different solvents: absolute ethanol, ethanol/water (7:3), honey brandy, mead, propylene glycol and water. The solvent influence on the chemical composition and antioxidant and antimicrobial activities of the extracts was investigated. Antioxidant potential was assessed by the DPPH free-radical-scavenging assay and the antimicrobial activity by the agar dilution method. Chemical composition of the extracts was determined in vitro by three colorimetric assays: total ortho-diphenols, phenolics and flavonoids contents and the LC-MS technique. To our knowledge, this is the first time that solvents such as honey brandy and mead have been studied. Honey brandy showed considerable potential to extract propolis active compounds able to inhibit the growth of bacteria such as the methicillin-sensitive Staphylococcus aureus and Propionibacterium acnes (MIC values of 100 and 200 µg/mL, respectively) and the fungi Candida albicans and Saccharomyces cerevisiae (MIC = 500 µg/mL, for both). Mead extracts displayed high antioxidant capacity (EC50 = 1.63 ± 0.27 µg/mL) and great activity against resistant bacteria such as the methicillin-resistant Staphylococcus aureus and Escherichia coli (MIC = 750 µg/mL, for both). The production of such solvents made from beehive products further promotes a diversification of apiary products and the exploration of new applications using eco-friendly solutions.

Phenolic Compounds Contribution to Portuguese Propolis Anti-Melanoma Activity

“…The G18 propolis extract was prepared with absolute ethanol (Fisher Chemical) to obtain G18.EE, as previously described by Freitas et al [ 40 ]. The ethanol extract (EE) was then dried by solvent evaporation (62% yield [ 41 ]) and stored at 4 °C, in the dark, until further use.…”

“…Propolis from Gerês, one of the most studied Portuguese propolis [ 40 , 41 , 42 , 43 , 44 , 45 , 46 ], displays high antioxidant and antimicrobial activities, regardless of the harvesting year [ 40 ]. An ethanol extract of propolis from Gerês collected in 2018 (G18.EE) and its three fractions—ethyl acetate (G18.EE-EtOAc), n -hexane (G18.EE- n -hexane), and n -butanol (G18.EE- n -BuOH)—promoted apoptosis mediated by ROS (reactive oxygen species) in melanoma, thus demonstrating to be cytotoxic to BRAF -mutated melanoma cell lines.…”

Modelling the In Vitro Growth of Phytopathogenic Filamentous Fungi and Oomycetes: The Gompertz Parameters as Robust Indicators of Propolis Antifungal Action

“…The results of TPC and TFC characterization are in line with the values reported by Silva et al [58] for an EE from The ethanolic extraction yield of sample A16 fits within the range of yields obtained by our research group for Portuguese propolis samples being closer to the upper limit (61.6% to 96.4%) (from a collection of unpublished studies of our investigation group). Lower yield values for propolis samples from the north of Portugal-61.6% [34] and 62% [55]were found. Similarly, the yield reported in this study is higher in comparison to the values of ethanol extracts from propolis samples of other countries, such as from China (51.03%) [56] and from Taiwanese green propolis (66.75%) [57].…”

“…Therefore, propolis is a natural product with biopesticide potential [28,29]. Portuguese propolis is generally included in the poplar European temperate type [26], produced from poplar exudates, mainly Populus nigra L., rich in flavonoid aglycones (flavones and flavanones), phenolic acids and their esters [20,25,[30][31][32][33][34]. However, Portugal exhibits a great botanical diversity and two different types of propolis were identified: a common temperate propolis type, observed in the north, central coast and Azores, with a high phenolic content, and a less common propolis, with lower phenolic content and an unusual composition in quercetin and kaempferol glycosides, characteristic of the central interior and south, with Cistus ladanifer L. being the main botanical source content [35][36][37].…”

Unlocking the Full Potential of Green Propolis: A Novel Extraction Approach Using Eutectic Solvents for Improved Phenolic Compound Recovery

“…Ethanol is the primary solvent used to produce propolis extracts on a large scale. ,, Unfortunately, ethanol has some drawbacks, such as residual flavor and inadequate application in some medical fields, including ophthalmology and pediatrics. , Additionally, it is not recommended for specific populations, such as Muslims, pregnant women, children, and people with alcohol intolerance. , Water is often used as an alternative solvent to ethanol, but it does not have an equivalent extraction performance. ,, Therefore, new strategies must be explored, considering the search for new solvents.…”