Poplar Buds—A Spring Salve for Wounds and Aches?

Aim of the study: Populus nigra L. (family Salicaceae) is one of the most common trees found in deciduous forests.

Results: Several studies have described its antioxidant, anti-inflammatory, antibacterial, antifungal, antidiabetic, antitumor, and hepatoprotective properties, its ability to lower uric acid, and its effects on melanin production. These findings suggest that black poplar buds are a valuable and important source of bioactive compounds responsible for a wide range of therapeutic uses. They are a promising complementary and/or alternative source for addressing many health problems. This review aims to gather existing information and provide an up-to-date account of the phytochemical and therapeutic uses of Populus nigra L. buds.

Aim of the study: The aim of this study was to assess the wound-healing potential of black poplar ointment containing 10 or 20% ethanolic extract of Populus nigra flower buds, using an excision model in rats.

Results: The results showed that the extract contained high amounts of total phenols (89.5 ± 7.7 mg caffeic acid equivalent/g of extract) and hydrolysable tannins (142.05 ± 2.55 mg tannic acid equivalent/g of extract), in correlation with strong DPPH (2,2-diphenyl-1-picrylhydrazyl) radical-scavenging activity and beta-carotene bleaching, with values of 96.31 ± 3.42 and 85.27 ± 1.79%, respectively. Anti-inflammatory potential was shown by inhibition of lipoxygenase and cyclooxygenase (52.80 ± 0.2 and 53.88 ± 2.55%, respectively). Treatment with Populus nigra ointment (10 and 20%) promoted wound contraction of 97.37 ± 1.19 and 97.28 ± 0.91%, respectively. The activities of the antioxidant marker enzymes catalase (0.10 ± 0.001; 0.08 ± 0.003 U/mg protein) and superoxide dismutase (363.34 ± 24.37; 317.82 ± 53.83 U/mg protein) in granulation tissue increased with treatment using 10 or 20% ointment, respectively.

Aim of the study: Poplar leaf buds (Populi gemmae) are traditionally used as anti-inflammatory agents to treat skin injuries or coughs. They differ in their chemical composition and types of activity, whose mechanisms are not fully understood. Evaluation and comparison of the anti-inflammatory activity of leaf-bud extracts from Populus nigra, P. × berolinensis and P.

Results: Several flavanones and phenolic acids with radical-scavenging properties were found in all the poplar bud extracts analyzed. Treatment with certain flavanones or extracts from buds of P. × berolinensis and P. nigra reduced the release of IL-6 and IL-1β in HGF-1 cells, and downregulated mRNA for both cytokines. COX-2 protein expression was observed with pinocembrin and P. × berolinensis buds. These effects were not observed with buds of P. lasiocarpa, which do not contain flavonoids. The study revealed the potential protective role of pinocembrin, pinostrobin, and extracts from P. nigra and P. × berolinensis buds against AgNP-induced inflammation and cytotoxicity in HGF-1 cells. The antioxidant properties of poplar bud extracts were also demonstrated. P. × berolinensis buds showed the highest activity in both the in vitro model and the bioautographic tests.

Aim of the study: Hydroalcoholic extracts obtained from buds of P. nigra, P.

Results: ABTS and DPPH assays showed that P. nigra had the strongest antioxidant activity, in line with its highest total phenolic content. Analysis of anti-inflammatory activity clearly showed that all extracts suppressed the production of key pro-inflammatory cytokines (IL-6, IL-1β, and TNF-α) and the inflammatory danger signal HMGB1. These results show that the extracts have antioxidant and significant anti-inflammatory activity, highlighting their potential as therapeutic agents.

Results: EECP and EEPB showed strong free-radical-scavenging activity and significant anti-inflammatory effects in vitro. They acted by regulating key inflammatory mediators of mRNA transcription, inhibiting the production of specific inflammatory cytokines, and blocking activation of nuclear factor (NF)-κB. Administration of EECP and EEPB (25 and 100 mg/kg) provided significant protection by reducing histopathological changes in the lungs and suppressing the production of LPS-stimulated inflammatory cytokines, including interleukin-6 (IL-6), IL-10, MCP-1, TNF-α, and IL-12p70, in mice with endotoxemia. The results show that Chinese propolis and poplar buds have potent anti-inflammatory properties and provide biological information that may help develop suitable substitutes for propolis in preventing and treating inflammatory diseases.

Aim of the study: The aim of this study was to evaluate the antioxidant potential, antimicrobial activity, in vitro anticancer effect (tested on the MCF-7 breast cancer cell line), and anti-angiogenic and immunomodulatory potential of Populus nigra L. bud (Pg) extract collected in western Romania.

Results: Populus nigra L. bud extract has significant antioxidant activity due to its rich phytochemical composition. Regarding biological activity, the results showed that poplar bud extract significantly inhibited Gram-positive bacteria and reduced MCF-7 tumor cell viability in a dose-dependent manner, with an IC50 of 66.26 μg/mL, while not affecting healthy cells. Early apoptotic events were detected by Annexin V-PI double staining at the maximum tested concentration (150 μg/mL). The extract induced G0/G1 phase cell-cycle arrest. In addition, Pg extract showed anti-angiogenic potential on the chorioallantoic membrane. At the highest concentration (150 μg/mL), it was well tolerated and showed no signs of toxicity to the vascular plexus. At low concentrations, Pg extract also had immunomodulatory activity in primary human dendritic cells by increasing IL-12 and IL-23 subunits.

Aim of the study: Poplar buds are characterized by a high content of phenolic compounds, which have a broad range of biological activities. However, the relationship between Chinese propolis and poplar buds, based on their antioxidant capacities and underlying mechanisms, remains unclear.

Results: They also reduced levels of reactive oxygen species (ROS) and malondialdehyde (MDA), while increasing the activity of antioxidant enzymes (SOD, CAT). PBE and CP treatment increased the expression of the key genes daf-16, sod-3, hsp-16.2, and skn-1 in nematodes. This suggests that the antioxidant activity of PBE and CP depends on the daf-16 and skn-1 signaling pathways. In conclusion, poplar bud extracts have the potential to become a substitute for propolis and a potential therapeutic agent for treating diseases associated with oxidative damage.

Aim of the study: Balsam poplar (Populus balsamifera L.) buds growing in Lithuania are a plant material rich in polyphenols, with a chemical composition similar to that of propolis. To potentially adapt extracts of this plant material for therapeutic purposes, detailed studies of the chemical composition and biological activity of balsam poplar buds are important.

Results: According to our research, extracts of balsam poplar buds collected in Lithuania are dominated by p-coumaric acid (496.9–13,291.2 µg/g), cinnamic acid (32.9–11,788.5 µg/g), pinobanksin (34.9–1775.5 µg/g), and salicin (215.3–1190.7 µg/g). The antioxidant activity of poplar buds was evaluated using ABTS (2,2-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)), DPPH (2,2-diphenyl-1-picrylhydrazyl), and FRAP (ferric-reducing antioxidant power) methods. All extracts showed antioxidant activity, and the results correlated with the amounts of total phenolic compounds in the extracts (ABTS r = 0.974; DPPH r = 0.986; FRAP r = 0.955, p < 0.01). Studies of antimicrobial activity showed that ethanolic extracts inhibited Staphylococcus aureus, Enterococcus faecalis, and Escherichia coli. The extracts had stronger antimicrobial activity against Gram-positive bacteria.

Aim of the study: Balsam poplar and black poplar (Populus balsamifera L. and Populus nigra L.) buds growing in Lithuania are the primary source of propolis. It is therefore appropriate to evaluate and compare the composition of these raw plant materials and propolis, both quantitatively and qualitatively.

Results: Propolis and balsam poplar bud extract are dominated by p-coumaric acid, while black poplar is dominated by caffeic acid. Antioxidant activity was evaluated using 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. All extracts showed antioxidant activity, and the results correlated with the amounts of phenolic compounds and flavonoids in the extracts. Studies of antimicrobial activity showed that all extracts inhibited the growth of Staphylococcus aureus and Candida albicans, with balsam poplar bud extract showing the strongest effect.

Aim of the study: The purpose of this study was to evaluate the tyrosinase-inhibiting capacity of Populus nigra bud absolute (PBA) and compare it with kojic acid (KA), a controversial reference tyrosinase inhibitor. Populus nigra buds were extracted with hexane and ethanol to obtain PBA.

Results: PBA reduces intracellular melanin levels, with a 50% decrease at 39±9ppm. Finally, PBA at 1000ppm lightens RHE and reduces their melanin content by 20%. PBA is a strong inhibitor of tyrosinase and reduces melanogenesis in B16F10 melanocytes. Thus, PBA may have applications in skin-lightening cosmetics.