Extracts of Poplar Buds (Populus balsamifera L., Populus nigra L.) and Lithuanian Propolis: Comparison of Their Composition and Biological Activities

Abstract

Balsam poplar and black poplar (Populus balsamifera L. and Populus nigra L.) buds that grow in Lithuania are the primary source of propolis, therefore it is proper to evaluate and compare the composition of these raw plant materials and propolis quantitatively and qualitatively. Propolis and balsamic poplar bud extract are dominated by p-coumaric acid and black poplar-caffeic acid. Antioxidant activity was evaluated by DPPH (2,2-diphenyl-1-picrylhydrazyl), ABTS (2,2-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid), FRAP (ferric-reducing antioxidant power) and CUPRAC (cupric reducing antioxidant capacity) methods and all extracts showed antioxidant activity, and obtained results correlated with the obtained amounts of phenolic compounds and flavonoids in the extracts. Studies of antimicrobial activity have shown that all extracts have a growth inhibitory effect against Staphylococcus aureus and Candida albicans, but the extract of balsam poplar buds showed the most significant effect of such kind. Considering the results of the research, it can be stated that balsam poplar buds cultured in Lithuania are the primary raw material of propolis, which is rich in phenolic compounds with antioxidant properties and is a promising raw material for pharmaceutical purposes.

Geographic Area of Collection Determines the Chemical Composition and Antimicrobial Potential of Three Extracts of Chilean Propolis

“…According to the direct comparison with commercial standards and the time of retention (Tr), the pinocembrin was verified as the most abundant compound present. In the three samples we identified the presence of other polyphenols such as galangin, quercetin, apigenin and caffeic acid phenethyl ester (CAPE); these results were similar to previous studies [ 13 , 14 , 15 ].…”

“…Chromatographic and spectrometric studies aimed at quantifying total compounds showed differences in the results in previous studies, where calibration curves were performed with caffeic acid and not gallic acid or catechin and not using a mixture of pinocembrin–galangin (2:1 proportion) using the Folin–Ciocalteu method. These flavanones and dihydroflavonols are the main components in poplar-type propolis, as described by several authors [ 3 , 15 ]…”

“…We used the serial dilution method, following the NCCLS guidelines [ 15 ]. The strains of Staphylococcus aureus ATCC 29213 and Escherichia coli ATCC 35218 determined the Minimum Inhibitory Concentration (MIC).…”

Ophthalmic In Situ Gels with Balsam Poplar Buds Extract: Formulation, Rheological Characterization, and Quality Evaluation

“…No statistically significant difference (p > 0.05) was determined between the amounts of active ingredients in the tested gels. The test results confirmed that the main components in poplar buds are phenolic acids and flavonoids [25]. The results of quantitative analysis showed that in situ gels with poplar buds extract could be used in ophthalmology as sources of polyphenolic compounds [81].…”

“…Balsam poplar buds, as with propolis, are a source of phenolic acids and flavonoids. Researchers have found that p -coumaric acid predominates in both ethanolic propolis and balsam poplar buds extracts collected in Lithuania [ 25 ]. Poplar buds, due to their antibacterial [ 26 ], antioxidant [ 27 ], and anti-inflammatory [ 28 ] action, are a potential active material in the production of eye drops.…”