Propolis volatile compounds: chemical diversity and biological activity: a review

Characterisation of New Zealand Propolis from Different Regions Based on Its Volatile Organic Compounds

Propolis is a bee product mainly consisting of plant resins and is used by bees to maintain the structural integrity of the colony. Propolis is known to contribute to bee health via its antimicrobial activity and is a valued product for human use owing to its nutritional and medicinal properties. Propolis is often characterised into seven categories depending on the resin source. New Zealand propolis is typically assumed as being poplar-type propolis, but few studies have chemically characterised New Zealand propolis to confirm or reject this assumption. Here, for the first time, we characterise propolis originating from different regions in New Zealand based on its volatile organic compounds, using gas chromatography coupled with mass spectrometry (GC-MS). To support this characterisation, we also collected and analysed resin samples from a variety of resin-producing plants (both native to New Zealand and introduced). Our findings suggest that bees mainly use poplar as a resin source, but also utilize native plant species to produce propolis. While regional variation did not allow for clear separation between samples, some patterns emerged, with samples from some regions having more chemical complexity and a higher contribution from native species (as suggested by a higher number of compounds unique to native species resin). Further studies are needed to accurately identify the botanical sources contributing to these samples. It may be also of interest to explore the biological activity of regional propolis samples and their potential nutritional or medicinal benefits.

Natural antibiotics against antimicrobial resistance: sources and bioinspired delivery systems

The current burden associated to multidrug resistance, and the emerging superbugs, result in a decreased and even loss of antibiotic efficacy, which poses significant challenges in the treatment of infectious diseases. This situation has created a high demand for the discovery of novel antibiotics that are both effective and safe. However, while antibiotics play a crucial role in preventing and treating diseases, they are also associated with adverse effects. The emergence of multidrug-resistant and the extensive appearance of drug-resistant microorganisms, has become one of the major hurdles in healthcare. Addressing this problem will require the development of at least 20 new antibiotics by 2060. However, the process of designing new antibiotics is time-consuming. To overcome the spread of drug-resistant microbes and infections, constant evaluation of innovative methods and new molecules is essential. Research is actively exploring alternative strategies, such as combination therapies, new drug delivery systems, and the repurposing of existing drugs. In addition, advancements in genomic and proteomic technologies are aiding in the identification of potential new drug targets and the discovery of new antibiotic compounds. In this review, we explore new sources of natural antibiotics from plants, algae other sources, and propose innovative bioinspired delivery systems for their use as an approach to promoting responsible antibiotic use and mitigate the spread of drug-resistant microbes and infections.

Extraction Kinetics of Brazilian Green Propolis and Chemical Characterization of its Volatiles

Propolis is a natural resinous product produced by Apis mellifera bees from the exudates of various plants. The color of propolis (green) is a consequence of its botanical origin, as bees collect young tissues and leaves of Baccaris dracunculifolia. This study evaluated the chemical composition and extraction kinetics of essential oils obtained from Brazilian green propolis by hydrodistillation. Hydrodistillation was performed for 360 min and analyzed at different times (30, 60, 120, 240, and 360 min), allowing the calculation of the accumulated content (% w/w) and the identification of the essential oil chemical profile. The GC/FID and GC/MS analysis led to the annotation of 60 compounds with estragole (13.30 %), benzyl propanoate (14.59 %), and (E)-nerolidol (13.57 %) as the main compounds. The optimum conditions for extraction of phenylpropanoids (PP), hydrocarbons (HD), monoterpenes (MT), and oxygenated monoterpenes (OMT) are between 30 and 120 min. In comparison, sesquiterpenes (ST) and oxygenated sesquiterpenes (OST) are extracted more efficiently between 240 and 360 min. The optimal extraction speed determination is essential for industrial-scale processing to obtain components such as sesquiterpenes, which have a high economic value in the cosmetic/perfumery and pharmaceutical industries.

Exploring Propolis as a Sustainable Bio-Preservative Agent to Control Foodborne Pathogens in Vacuum-Packed Cooked Ham

The search for natural food additives makes propolis an exciting alternative due to its known antimicrobial activity. This work aims to investigate propolis' behavior as a nitrite substitute ingredient in cooked ham (a ready-to-eat product) when confronted with pathogenic microorganisms of food interest. The microbial evolution of Listeria monocytogenes, Staphylococcus aureus, Bacillus cereus, and Clostridium sporogenes inoculated at known doses was examined in different batches of cooked ham. The design of a challenge test according to their shelf life (45 days), pH values, and water activity allowed the determination of the mesophilic aerobic flora, psychotropic, and acid lactic bacteria viability. The test was completed with an organoleptic analysis of the samples, considering possible alterations in color and texture. The cooked ham formulation containing propolis instead of nitrites limited the potential growth (δ < 0.5 log10) of all the inoculated microorganisms until day 45, except for L. monocytogenes, which in turn exhibited a bacteriostatic effect between day 7 and 30 of the storage time. The sensory analysis revealed the consumer's acceptance of cooked ham batches including propolis as a natural additive. These findings suggest the functionality of propolis as a promising alternative to artificial preservatives for ensuring food safety and reducing the proliferation risk of foodborne pathogens in ready-to-eat products.

Volatile profile of bee bread

Bee bread is one of the least studied bee products. In this study, ten bee bread samples were characterized using palynology and HS-SPME-GC-MS (headspace solid-phase microextraction gas chromatography-mass spectrometry). In total, over one hundred different volatile components were identified, belonging to different chemical groups. Only ten common components were detected in all the samples. These volatiles were ethanol, ethylene chloride, ethyl acetate, acetic acid, α-pinene, furfural, nonane, nonanal, n-hexane and isovaleric acid. Several other components were commonly shared among various bee bread samples. Over sixty detected compounds have not been previously reported in bee bread. The analysis required a mild extraction temperature of 40 °C, as higher temperatures resulted in the Maillard reaction, leading to the production of furfural. The profile of volatile compounds of the tested bee pollen samples was complex and varied. Some relationships have been shown between botanical origin and volatile organic compound profile.

Evaluation of calcium hydroxide mixed with propolis by ultrasonic activation as root canal dressing in delayed tooth replantation

Background

In cases of tooth avulsion, in which the neurovascular bundle responsible for nourishing the dental pulp is break, endodontic treatment is necessary before proceeding with tooth replantation. In this process, various substances have been tested in combination with calcium hydroxide Ca(OH)2 in an attempt to improve its effectiveness. This study aimed to examine the effects of using a mixture of Ca(OH)2 and 10% propolis, with subsequent application of ultrasonic treatment, on the delayed replantation of teeth in rats.

Material and Methods

Twenty-four rats underwent a surgical procedure to extract the upper right incisor, leaving it on a surface to dry for one hour. The pulp and periodontal ligament were removed and the teeth were submerged in a 2% sodium fluoride acidulated phosphate solution. The canals were dehydrated using paper cones and the teeth were divided into four groups, according to the type of intracanal dressing: Ca(OH)2 group, Ca(OH)2 group with ultrasonic agitation, Ca(OH)2 and propolis group, Ca(OH)2 and propolis group with ultrasonic agitation. The root canals were irrigated with saline solution and the teeth were reimplanted. Sixty days after reimplantation, the animals were euthanized.

Results

With regard to the presence of acute and chronic inflammatory infiltrate in the periodontal ligament, there was no statistically significant difference among some of the groups. Root resorption was identified in all groups, and there was no significant difference between them.

Conclusions

It is concluded that the application of intracanal dressing containing Ca(OH)2 associated with 10% propolis, followed by ultrasonic agitation, did not prove to be more effective than the use of Ca(OH)2 alone in the repair process in the delayed replantation of rat teeth. Key words:Tooth replantation, Calcium hydroxide, Propolis, Ultrasound, Intracanal dressing.

Effects of caatinga propolis from Mimosa tenuiflora and its constituents (santin, sakuranetin and kaempferide) on human immune cells

ETHNOPHARMACOLOGICAL RELEVANCE

Propolis is a bee product used in folk medicine to treat inflammatory diseases. Diverse types of propolis are produced worldwide depending on the local flora. Recently, research has been focused on a propolis sample produced in the northeast Brazilian "caatinga" from Mimosa tenuiflora, popularly known as "jurema-preta".

AIM OF THE STUDY

A possible immunomodulatory/anti-inflammatory action was analyzed to verify the potential of M. tenuiflora propolis (MP) and its constituents (santin, sakuranetin and kaempferide) in human immune cells under baseline conditions or in LPS-stimulated cells.

METHODS

Cell viability, cytokine (TNF-α, IL-1β, IL-6, IL-8, IL-10) production and intracellular pathways (NF-kB and p38 MAPK) were evaluated.

RESULTS

Under basal conditions, MP and sakuranetin did not affect cytokine production; santin enhanced TNF-α, IL-1β, IL-6, while kaempferide inhibited IL-8 and IL-10. In LPS-stimulated cells, MP and its compounds exerted an inhibitory activity on TNF-α and IL-1β, while no effects were seen on IL-6 and IL-8. Santin and kaempferide inhibited IL-10 production. No significant differences were seen on NF-kB and p38 MAPK intracellular pathways.

CONCLUSION

Data indicated the immunomodulatory action of caatinga propolis and its constituents at noncytotoxic concentrations, specifically an anti-inflammatory activity in LPS-treated cells by inhibiting cytokine production. Santin, sakuranetin and kaempferide appeared to be involved in MP activities.

Comparative evaluation of propolis mouthwash with 0.2% chlorhexidine mouthwash as an adjunct to mechanical therapy in improving the periodontitis among perimenopausal women: a randomized controlled trial

OBJECTIVE

To evaluate the efficacy of Propolis mouthwash compared to chlorhexidine mouthwash as an adjunct to mechanical therapy in improving clinical parameters in perimenopausal women with chronic periodontitis.

METHODOLOGY

A double-blind, randomized, controlled clinical trial was conducted by recruiting 144 subjects with mild to moderate chronic periodontitis. After scaling and root planning, subjects were allocated to two treatment groups: 0.2% chlorhexidine mouthwash and 20% propolis mouthwash twice daily for six weeks. Clinical parameters such as pocket probing depth (PPD), clinical attachment loss (CAL) and bleeding on probing (BOP) were analysed at baseline, six weeks, and 12 weeks.

RESULT

The mean value of PPD in the propolis group was 4.67 at baseline, reduced to 4.01 at six weeks and 3.59 at 12 weeks. While in the chlorhexidine group, the baseline value of 4.65 reduced to 4.44 and 4.25 at six weeks and 12 weeks, respectively. The baseline value of the mean CAL in the propolis group was 4.45. This value was reduced to 4.15 at six weeks and 3.77 at 12 weeks. For the chlorhexidine group, the baseline value of CAL was 4.80, which was reduced to 4.50 and 4.19 at six weeks and 12 weeks. The mean value of bleeding on probing in the propolis group was 77.20, which decreased to 46.30 at six weeks and 14.60 at the final visit. In the chlorhexidine group, the mean value of 77.30 was reduced to 49.60 and 22.80 at subsequent visits.

CONCLUSION

This study concludes that both propolis and chlorhexidine mouthwash positively improve clinical parameters; however, propolis is significantly more effective in improving BOP.

TRIAL REGISTRATION

ID: NCT05870059, Date of Registration: 02/02/2022. ( https://beta.

CLINICALTRIALS

gov/study/NCT05870059 ).

The Identification of Bee Comb Cell Contents Using Semiconductor Gas Sensors

Beekeeping is an extremely difficult field of agriculture. It requires efficient management of the bee nest so that the bee colony can develop efficiently and produce as much honey and other bee products as possible. The beekeeper, therefore, must constantly monitor the contents of the bee comb. At the University of Warmia and Mazury in Olsztyn, research is being carried out to develop methods for efficient management of the apiary. One of our research goals was to test whether a gas detector (MCA-8) based on six semiconductor sensors-TGS823, TGS826, TGS832, TGS2600, TGS2602, and TGS2603 from the company FIGARO-is able to recognize the contents of bee comb cells. For this purpose, polystyrene and wooden test chambers were created, in which fragments of bee comb with different contents were placed. Gas samples were analyzed from an empty comb, a comb with sealed brood, a comb with open brood, a comb with carbohydrate food in the form of sugar syrup, and a comb with bee bread. In addition, a sample of gas from an empty chamber was tested. The results in two variants were analyzed: (1) Variant 1, the value of 270 s of sensor readings from the sample measurement (exposure phase), and (2) Variant 2, the value of 270 s of sensor readings from the sample measurement (measurement phase) with baseline correction by subtracting the last 600 s of surrounding air measurements (flushing phase). A five-time cross-validation 2 (5xCV2) test and the Monte Carlo cross-validation 25 (trained and tested 25 times) were performed. Fourteen classifiers were tested. The naive Bayes classifier (NB) proved to be the most effective method for distinguishing individual classes from others. The MCA-8 device brilliantly differentiates an empty comb from a comb with contents. It differentiates better between an empty comb and a comb with brood, with results of more than 83%. Lower class accuracy was obtained when distinguishing an empty comb from a comb with food and a comb with bee bread, with results of less than 73%. The matrix of six TGS sensors in the device shows promising versatility in distinguishing between various types of brood and food found in bee comb cells. This capability, though still developing, positions the MCA-8 device as a potentially invaluable tool for enhancing the efficiency and effectiveness of beekeepers in the future.

Differences in the biochemical content and radical scavenging activity of propolis from different parts of a Meliponula ferruginea hive

Research on stingless bee products has increased in recent years, and of particular interest is propolis because of its biological activities such as antioxidant and antimicrobial. However, there is paucity of information regarding intra-hive variations in the biochemical composition and biofunctional properties of this propolis. In this study, we investigated the phytochemicals and radical scavenging activity (RSA) of Meliponula ferruginea propolis from 10 wooden hives (n = 49). The samples were collected from five different locations comprising the entrance, involucrum, pillars, pots and sealant. Principal component analysis showed that there is an intra-hive variation in phytochemical content and RSA. Phenolic content constituted the highest phytochemical content in all the locations. The sealant and entrance had the highest amounts of phytochemicals compared to the involucrum, pillars and pots. Further analysis of propolis extracts by gas chromatography-mass spectrometry revealed occurrence of different compounds such as monoterpenoids, hydrocarbons, triterpenoids and alkaloids. Hydrocarbons were common in all parts while monoterpenes and triterpenes were present in the entrance. The findings of our study indicates that there is an intra-hive variation in propolis of M. ferruginea and hence this information will provide further insight into better understanding of stingless bee propolis.

Examination of Raw Samples and Ethanol Extracts of Gerês Propolis Collected in Different Years

Propolis, a natural resin created by bees, has garnered significant attention from both the scientific community and industry due to an impressive range of bioactivities. Nonetheless, the intrinsic variability in its chemical composition and bioactive profiles has been hindering propolis' full potential use. We previously showed that ethanol extracts (EEs) of a Portuguese propolis sample (Gerês) collected over four consecutive years displayed similar chemical and biological profiles, a constancy never documented before. However, the characteristics of the unprocessed samples of Gerês propolis were never described. Hence, the central objective of this study is to assess the quality parameters of unprocessed propolis samples collected from Gerês (G), over a four-year period (2019-2022), alongside the analysis of the chemical composition and bioactivities of the EEs prepared with the same raw samples. The ash, wax, balsam and water contents of the unprocessed samples-G19 to G22-showed minor fluctuations, likely attributed to uncontrollable natural events impacting the propolis source and collection process. On the other hand, the antimicrobial and antioxidant activities of all the four ethanol extracts (G19.EE-G22.EE) consistently align with prior studies. Furthermore, the Gerês propolis extracts showed remarkable uniformity in chemical composition parameters too, particularly concerning total polyphenol, flavonoid and ortho-diphenol contents. In summary, our research reinforces the beneficial properties of propolis and show that extracts' bioactivities remain within the reference ranges for Gerês propolis, despite minor differences in unprocessed samples, suggesting a consistent action over time. Thus, this work could be instrumental towards the establishment of standard parameters for propolis applications, offering valuable insights to this field of propolis research.

Activity of propolis from Mexico on the proliferation and virulence factors of Candida albicans

BACKGROUND

This research evaluated the anti-Candida albicans effect of Mexican propolis from Chihuahua. Chemical composition of the ethanolic extract of propolis was determined by GC-MS, HPLC-DAD, and HPLC-MS. The presence of anthraquinone, aromatic acid, fatty acids, flavonoids, and carbohydrates was revealed.

RESULTS

The anti-Candida activity of propolis was determined. The inhibitions halos were between 10.0 to 11.8 mm; 25% minimum inhibitory concentration (0.5 mg/ml) was fungistatic, and 50% minimum inhibitory concentration (1.0 mg/ml) was fungicidal. The effect of propolis on the capability of C. albicans to change its morphology was evaluated. 25% minimum inhibitory concentration inhibited to 50% of germ tube formation. Staining with calcofluor-white and propidium iodide was performed, showing that the propolis affected the integrity of the cell membrane. INT1 gene expression was evaluated by qRT-PCR. Propolis significantly inhibited the expression of the INT1 gene encodes an adhesin (Int1p). Chihuahua propolis extract inhibited the proliferation of Candida albicans, the development of the germ tube, and the synthesis of adhesin INT1.

CONCLUSIONS

Given the properties demonstrated for Chihuahua propolis, we propose that it is a candidate to be considered as an ideal antifungal agent to help treat this infection since it would not have the toxic effects of conventional antifungals.

Exploring the Functional Properties of Propolis, Geopropolis, and Cerumen, with a Special Emphasis on Their Antimicrobial Effects

Bee propolis has been touted as a natural antimicrobial agent with the potential to replace antibiotics. Numerous reports and reviews have highlighted the functionalities and applications of the natural compound. Despite much clamor for the downstream application of propolis, there remain many grounds to cover, especially in the upstream production, and factors affecting the quality of the propolis. Moreover, geopropolis and cerumen, akin to propolis, hold promise for diverse human applications, yet their benefits and intricate manufacturing processes remain subjects of intensive research. Specialized cement bees are pivotal in gathering and transporting plant resins from suitable sources to their nests. Contrary to common belief, these resins are directly applied within the hive, smoothed out by cement bees, and blended with beeswax and trace components to create raw propolis. Beekeepers subsequently harvest and perform the extraction of the raw propolis to form the final propolis extract that is sold on the market. As a result of the production process, intrinsic and extrinsic factors, such as botanical origins, bee species, and the extraction process, have a direct impact on the quality of the final propolis extract. Towards the end of this paper, a section is dedicated to highlighting the antimicrobial potency of propolis extract.

Bee Species, Botanical Sources and the Chemical Composition of Propolis from Yucatan, Mexico

Propolis is used by corbiculated bees to protect the bee hive; it is mostly used to seal cracks, to reduce or prevent microbial growth and to embalm invaders. Different factors have been reported to influence the chemical composition of propolis, including bee species and the flora surrounding the hive. Nevertheless, the majority of the studies are focused on propolis produced by Apis mellifera, while studies on the chemical composition of propolis produced by stingless bees are still limited. In this investigation, the chemical composition of 27 propolis samples collected in the Yucatan Peninsula from A. mellifera beehives, together with 18 propolis samples from six different species of stingless bees, were analyzed by GC-MS. Results showed that lupeol acetate and β-amyrin were the characteristic triterpenes in propolis samples from A. mellifera, while grandiflorenic acid and its methyl ester were the main metabolites present in samples from stingless bees. Multivariate analyses were used to explore the relationship between bee species and botanical sources on the chemical composition of the propolis samples. Differences in body size and, therefore, foraging abilities, as well as preferences for specific botanical sources among bee species, could explain the observed variation in propolis chemical composition. This is the first report on the composition of propolis samples from the stingless bees Trigona nigra, Scaptotrigona pectoralis, Nannotrigona perilampoides, Plebeia frontalis and Partamona bilineata.

Composition, Antibiofilm, and Antibacterial Potential of Volatile Oils from Geopropolis of Different Stingless Bees' Species

We aimed to characterize and investigate the antibacterial potential of the native stingless bees geopropolis volatile oils (VO) for the search of potentially new bioactive compounds. Geopropolis samples from Melipona bicolor schencki, M. compressipes manaosensis, M. fasciculata, M. quadrifasciata, M. marginata and M. seminigra merrillae were collected from hives in South Brazil. VO were obtained by hydrodistillation and characterised by gas chromatography coupled to mass spectrometry (GC/MS). Antimicrobial activity was assessed by microplate dilution method. The lowest MIC against cell walled bacteria was 219±0 μg mL-1 from M. quadrifasciata geopropolis VO with Staphylococcus aureus. The M. b. schencki geopropolis VO minimal inhibition concentration (MIC) was 424±0 μg mL-1 against all the mycoplasma strains evaluated. Fractionation resulted in the reduction of 50 % of the MIC value from the original oil. However, its compounds' synergism seems to be essential to this activity. Antibiofilm assays demonstrated 15.25 % eradication activity and 13.20 % inhibition of biofilm formation after 24 h for one subfraction at 2× its MIC as the best results found. This may be one of the essential mechanisms by which geopropolis VOs perform their antimicrobial activity.

Botanical Origins and Antioxidant Activities of Two Types of Flavonoid-Rich Poplar-Type Propolis

(1) Background: Propolis has attracted attention in recent years due to its important pharmacological effects. The present study aimed to investigate the botanical origins of 39 propolis samples and evaluate their antioxidant activities; (2) Methods: A HPLC-PDA system was used to analyze the phenolic compositions of propolis and poplar bud resin samples. The antioxidant activities of propolis samples were evaluated by oxygen radical absorption capacity (ORAC) and superoxide anion free radical scavenging capacity assay; (3) Results: Our study shows that 17 propolis samples were characterized by five predominant flavonoids, including 5-methoxy pinobanksin, pinobanksin, pinocembrin, pinobanksin-3-acetate, and chrysin, while 22 propolis samples were characterized by four flavonoids (pinobanksin, pinocembrin, pinobanksin-3-acetate, and chrysin). The average contents of characteristic flavonoids reached up to over 70% and 65% of total phenolics, respectively. Furthermore, the botanical origins of the two types of propolis samples were identified as Populus × euramericana cv. 'Neva' and Populus Simonii × P. nigra, respectively; (4) Conclusions: Most notably, our results reveal that these propolis samples presented excellent antioxidant activities due to their high contents of flavonoid. These flavonoid-rich propolis samples can thus be used to develop low-allergen and high-antioxidant nutraceuticals.

An in vitro anti-inflammatory effect of Thai propolis in human dental pulp cells

OBJECTIVE

To explore the potential for development of Thai propolis extract as a pulp capping agent to suppress pulpal inflammation from dental pulp infections. This study aimed to examine the anti-inflammatory effect of the propolis extract on the arachidonic acid pathway, activated by interleukin (IL)-1β, in cultured human dental pulp cells.

METHODOLOGY

Dental pulp cells, isolated from three freshly extracted third molars, were first characterized for their mesenchymal origin and treated with 10 ng/ml of IL-1β in the presence or absence of non-toxic concentrations of the extract from 0.08 to 1.25 mg/ml, as determined by the PrestoBlue cytotoxic assay. Total RNA was harvested and analyzed for mRNA expressions of 5-lipoxygenase (5-LOX) and cyclooxygenase-2 (COX-2). Western blot hybridization was performed to investigate COX-2 protein expression. Culture supernatants were assayed for released prostaglandin E2 levels. Immunofluorescence was conducted to determine involvement of nuclear factor-kappaB (NF-kB) in the inhibitory effect of the extract.

RESULTS

Stimulation of the pulp cells with IL-1β resulted in the activation of arachidonic acid metabolism via COX-2, but not 5-LOX. Incubation with various non-toxic concentrations of the propolis extract significantly inhibited upregulated COX-2 mRNA and protein expressions upon treatment with IL-1β (p<0.05), resulting in a significant decrease in elevated PGE2 levels (p<0.05). Nuclear translocation of the p50 and the p65 subunits of NF-kB upon treatment with IL-1β was also blocked by incubation with the extract.

CONCLUSIONS

Upregulated COX-2 expression and enhanced PGE2 synthesis upon treatment with IL-1β in human dental pulp cells were suppressed by incubation with non-toxic doses of Thai propolis extract via involvement of the NF-kB activation. This extract could be therapeutically used as a pulp capping material due to its anti-inflammatory properties.

A Systematic Review of the Potential Effects of Propolis Extracts on Experimentally-induced Diabetes

Oxidative stress (OS) is involved in the development of diabetes mellitus (DM) and its complications. Thus, OS reduction may be an important strategy for DM therapy. Propolis is bee resins with high antioxidant activity and is used in the treatment of different diseases, including DM. Therefore, in this systematic review, we evaluated the impact of propolis administration in diabetic animals. We used the PRISMA strategy to collect preclinical studies published in English up to November 2021 in three databases (PubMed/Medline, Scopus, and Web of Science). We used the SYRCLE tool to analyze the risk of methodological bias. Our primary search returned 198 studies, of which 14 were considered eligible to be included in this review. The administration of propolis induced a hypoglycemic effect in the treated animals, which is probably due to the reduction of OS. The animals showed restoration of endogenous antioxidant defenses and reduced levels of markers for OS. The administration of propolis resulted in improvement in the lipid profile of treated animals. Our risk of bias assessment showed a methodological quality score of less than 30% due to a lack of randomization, blinding, and proper allocation of animals. Heterogeneity in treatments, lack of results, and use of non-standard extracts are limitations in our data analysis. Despite these limitations, propolis induced a significant hypoglycemic effect in diabetic animals when compared to untreated controls. This effect was associated with a reduction in OS, a process mediated by ROS neutralization and restoration of endogenous antioxidant defenses.

Elemental Profile of Propolis from Different Areas of Serbia

Propolis is a resinous natural substance collected by honeybees from different plant sources. The element content of propolis is influenced by the content of elements in the soil, climatic factors, and the degree of pollution. The aim of the study was to characterize element composition and content of toxic elements in 51 propolis collected from different locations in Serbia and to evaluate the differences among them. Determination of the 21 elements were performed using Inductively coupled plasma - optical emission spectrometry. K was the most abundant element, followed by Ca, Mg, Si, Fe, Zn, and Al. The microelements B, Ba, Mn, Na, Pb, and Ti were also present in propolis, while Co, Cr, Cu, Mo, Ni, Sr, and V were found in trace. Toxic elements such as Pb, As, and Cd were found in the trace. Kruskal-Wallis tests differentiate groups of samples by geographical origin. The presence of B, Fe, Sr, Ti, Zn, and As demonstrated statistical significance between six regions of Serbia.

Preparation and Investigation of Thermally Annealed Zein-Propolis Electrospun Nanofibers for Biomedical Applications

Zein, a corn-derived protein, has a variety of applications ranging from drug delivery to tissue engineering and wound healing. This work aims to develop a biocompatible scaffold for dermal applications based on thermally annealed electrospun propolis-loaded zein nanofibers. Pristine fibers' biocompatibility is determined in vitro. Next, propolis from Melipona quadrifasciata is added to the fibers at different concentrations (5% to 25%), and the scaffolds are studied. The physicochemical properties of zein/propolis precursor dispersions are evaluated and the results are correlated to the fibers' properties. Due to zein's and propolis' very favorable interactions, which are responsible for the increase in the dispersions surface tension, nanometric size ribbon-like fibers ranging from 420 to 575 nm are obtained. The fiber's hydrophobicity is not dependent on propolis concentration and increases with the annealing procedure. Propolis inhibitory concentration (IC₅₀ ) is determined as 61.78 µg mL^-1 . When loaded into fibers, propolis is gradually delivered to cells as Balb/3T3 fibroblasts and are able to adhere, grow, and interact with pristine and propolis-loaded fibers, and cytotoxicity is not observed. Therefore, the zein-propolis nanofibers are considered biocompatible and safe. The results are promising and provide prospects for the development of wound-healing nanofiber patches-one of propolis' main applications.

Advances in the Elemental Composition Analysis of Propolis Samples from Different Regions of Turkey by X-Ray Fluorescence Spectrometry

In this study, it was aimed to determine the elemental composition of 47 propolis samples collected from different regions of Turkey by X-ray fluorescence spectroscopy. According to the results, the most abundant elements in propolis samples were the Ca, K, and Si with the mean values as 1556, 1383, and 731 mg/kg, respectively. Additionally, there were high degrees of positive and strong correlations of Al with S (0.925) and Fe (0.926) and Ca with Mg (0.970). According to cluster analysis results, the Aegean, Marmara, and Mediterranean regions showed strong similarities, whereas Southeastern Anatolia propolis samples were remarkably different. The elements considered as toxic for human and environmental health such as Mn, Ni, Pb, Sn, and W were at the trace amounts as < 10 mg/kg. When assuming 1 g raw propolis is consumed daily by a 60-kg adult, the analyzed propolis samples were not a source carrying the negative effects of these elements. However, they could be an indicator of environmental pollution.

Determination of Botanical Origin and Mineral Content of Propolis Samples from Balveren (Şırnak) Beekeepers Accommodation Areas

Researches on bee products have become popular in recent years. In fact, the content and component of bee products varies depending on many ecological and floristic factors and its nutritional and therapeutic properties are directly related to its content. Balveren (Şırnak province) beekeepers place their hives in locations with different geographical structure, floristic and topographic characteristics. This variability not only affects the quality of honey but also changes the properties of propolis. Studies on propolis, known as bee glue, have gained importance in recent years. As with other bee products, the propolis content also depends on the floristic characteristics of the region. In this study, propolis samples were collected from the regions where Balveren beekeepers stayed and their botanical origins, wax ratios, phenolic content, and mineral substance contents were analyzed. In the microscopic analysis, pollen grains belonging to 14 different families used by bees were determined. It was determined that the total phenolic and mineral contents of propolis vary completely depending on the location. With this study, the propolis properties of the hives in the region were tried to be revealed and it was aimed that this study would help the region's propolis to be used for technological and therapeutic purposes.

Antimicrobial Activity of Propolis from the Brazilian Stingless Bees Melipona quadrifasciata anthidioides and Scaptotrigona depilis (Hymenoptera, Apidae, Meliponini)

Melipona quadrifasciata anthidioides and Scaptotrigona depilis are species of stingless bees capable of producing propolis, which has considerable bioprospecting potential. In this context, the objective of this study was to determine the chemical compositions and evaluate the antimicrobial activity of propolis produced by M. q. anthidioides and S. depilis. The ethanolic extracts of propolis of M. q. anthidioides (EEP-M) and S. depilis (EEP-S) were prepared, and their chemical constituents were characterized by HPLC-ESI-MS. The antimicrobial activity was evaluated against bacteria and fungi, isolated from reference strains and hospital origin resistant to the action of antibiotics. From EEP-M, phenolic compounds were annotated, including gallic acid, ellagic acid, and flavonoids, as well as diterpenes and triterpenes. EEP-S showed mainly triterpene in its chemical composition. Both extracts inhibited the growth of medically relevant bacteria and fungi, including hospital-acquired and antimicrobial-resistant. In general, EEP-S showed better antimicrobial activity compared to EEP-M. The MIC of EEP-S against vancomycin-resistant Enterococcus faecalis was 3.50 mg/mL, while the MIC of EEP-M was 5.33 ± 0.16 mg/mL. In conclusion, this study shows that propolis produced by M. q. anthidioides and S. depilis has the potential to be used for the prevention or treatment of microbial infections.

Biological Activity and Chemical Composition of Propolis from Various Regions of Poland

Propolis is one of the bee products, with multiple biological properties used in numerous applications. The research objective was to determine the chemical composition and biological properties (antibacterial, antifungal, antiviral, antioxidant, and cytoprotective activity) of propolis extracts collected from various regions of Poland. The results indicated that the total content of phenols (116.16-219.41 mg GAE/g EEP) and flavonoids (29.63-106.07 mg QE/g EEP) in propolis extracts depended on their geographic origin. The high content of epicatechin, catechin, pinobanksin, myricetin, and acids: vanillic and syringic in propolis samples was confirmed by chromatographic analysis. Moreover, the presence of caffeic acid phenethyl ester was confirmed in all samples. The origin of propolis also influenced the biological properties of its extracts. The propolis extracts were characterized by moderate DPPH free radical scavenging activity (29.22-35.14%), and relatively low ferrous iron chelating activity (9.33-32.32%). The results indicated also that the propolis extracts showed high activity in the protection of human red blood cells against free radicals generated from 2,2'-azobis(2-methylpropionamidine) dihydrochloride (AAPH). The extracts exhibited diversified activity against the tested pathogenic bacteria and limited activity against fungal strains. The research of selected propolis extracts showed that only 2 of 5 examined samples showed moderate activity against HPV (human papillomaviruses) and the activity depended on its geographical distribution.

Evaluation of Chemical Composition, Sun Protection Factor and Antioxidant Activity of Lithuanian Propolis and Its Plant Precursors

The growing interest in polyphenols of natural origin and their plant sources encourages the study of their chemical composition and biological activity. Propolis is widely used as a source of phenolic compounds. The aim of this study is to evaluate and compare the chemical composition, antioxidant activity and sun protection factor (SPF) of the ethanolic extracts of the poplar buds, birch buds and pine buds of propolis plant precursors collected in Lithuania. The IC50 concentration of the extracts was evaluated using DPPH and ABTS methods. Extracts of poplar buds, birch buds and propolis showed a lower IC50 concentration by ABTS and DPPH methods compared with pine buds extracts. Poplar buds and propolis extracts showed the highest SPF value, while birch and pine buds extracts showed a lower SPF value. High-performance liquid chromatography (HPLC) analysis results showed that phenolic acids, such as p-coumaric acid and cinnamic acid, and flavonoids, such as pinobanksin and pinocembrin, were identified in all the tested extracts. Salicin has been identified only in poplar buds extracts. The results of antioxidant activity showed that propolis poplar and birch buds are a promising source of biologically active polyphenols.

Neutrophil Immunomodulatory Activity of Nerolidol, a Major Component of Essential Oils from Populus balsamifera Buds and Propolis

Propolis is a resinous mixture of substances collected and processed from various botanical sources by honeybees. Black poplar (Populus balsamifera L.) buds are one of the primary sources of propolis. Despite their reported therapeutic properties, little is known about the innate immunomodulatory activity of essential oils from P. balsamifera and propolis. In the present studies, essential oils were isolated from the buds of P. balsamifera and propolis collected in Montana. The main components of the essential oil from P. balsamifera were E-nerolidol (64.0%), 1,8-cineole (10.8%), benzyl benzoate (3.7%), α-terpinyl acetate (2.7%), α-pinene (1.8%), o-methyl anisol (1.8%), salicylaldehyde (1.8%), and benzyl salicylate (1.6%). Likewise, the essential oil from propolis was enriched with E-nerolidol (14.4%), cabreuva oxide-VI (7.9%), α-bisabolol (7.1%), benzyl benzoate (6.1%), β-eudesmol (3.6%), T-cadinol (3.1%), 2-methyl-3-buten-2-ol (3.1%), α-eudesmol (3.0%), fokienol (2.2%), nerolidol oxide derivative (1.9%), decanal (1.8%), 3-butenyl benzene (1.5%), 1,4-dihydronaphthalene (1.5%), selina-4,11-diene (1.5%), α-cadinol (1.5%), linalool (1.4%), γ-cadinene (1.4%), 2-phenylethyl-2-methyl butyrate (1.4%), 2-methyl-2-butenol (1.3%), octanal (1.1%), benzylacetone (1.1%), and eremoligenol (1.1%). A comparison between P. balsamifera and propolis essential oils demonstrated that 22 compounds were found in both essential oil samples. Both were enriched in E-nerolidol and its derivatives, including cabreuva oxide VI and nerolidol oxides. P. balsamifera and propolis essential oils and pure nerolidol activated Ca²⁺ influx in human neutrophils. Since these treatments activated neutrophils, the essential oil samples were also evaluated for their ability to down-regulate the neutrophil responses to subsequent agonist activation. Indeed, treatment with P. balsamifera and propolis essential oils inhibited subsequent activation of these cells by the N-formyl peptide receptor 1 (FPR1) agonist fMLF and the FPR2 agonist WKYMVM. Likewise, nerolidol inhibited human neutrophil activation induced by fMLF (IC₅₀ = 4.0 μM) and WKYMVM (IC₅₀ = 3.7 μM). Pretreatment with the essential oils and nerolidol also inhibited human neutrophil chemotaxis induced by fMLF, again suggesting that these treatments down-regulated human neutrophil responses to inflammatory chemoattractants. Finally, reverse pharmacophore mapping predicted several potential kinase targets for nerolidol. Thus, our studies have identified nerolidol as a potential anti-inflammatory modulator of human neutrophils.

Honeycomb, a New Food Resource with Health Care Functions: The Difference of Volatile Compounds found in Apis cerana and A. mellifera Honeycombs

The honeycomb composition is very complex, containing honey, royal jelly, pollen, and propolis, and thus contains a large number of bioactive ingredients, such as polyphenols and flavonoids. In recent years, honeycomb as a new functional food resource has been favored by many bee product companies, but the basic research on honeycomb is lacking. The aim of this study is to reveal the chemical differences between A. cerana honeycombs (ACC) and A. mellifera honeycombs (AMC). In this paper, we studied the volatile organic components (VOCs) of ACC and AMC by solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME/GC-MS). A total of 114 VOCs were identified in 10 honeycombs. Furthermore, principal component analysis (PCA) revealed that the chemical composition of ACC and AMC were different. Additionally, orthogonal partial least squares discrimination analysis (OPLS-DA) revealed that benzaldehyde, octanal, limonene, ocimene, linalool, α-terpineol, and decanal are the significant VOCs in AMC extracts, which are mainly derived from propolis. OPLS-DA model also identified 2-phenylethanol, phenethyl acetate, isophorone, 4-oxoisophorone, betula, ethyl phenylacetate, ethyl palmitate, and dihydrooxophorone as potential discriminatory markers of ACC, which likely contribute to protecting the hive against microorganisms and keep it clean.

Propolis efficacy on SARS-COV viruses: a review on antimicrobial activities and molecular simulations

This current study review provides a brief review of a natural bee product known as propolis and its relevance toward combating SARS-CoV viruses. Propolis has been utilized in medicinal products for centuries due to its excellent biological properties. These include anti-oxidant, immunomodulatory, anti-inflammatory, anti-viral, anti-fungal, and bactericidal activities. Furthermore, studies on molecular simulations show that flavonoids in propolis may reduce viral replication. While further research is needed to validate this theory, it has been observed that COVID-19 patients receiving propolis show earlier viral clearance, enhanced symptom recovery, quicker discharge from hospitals, and a reduced mortality rate relative to other patients. As a result, it appears that propolis could probably be useful in the treatment of SARS-CoV-2-infected patients. Therefore, this review sought to explore the natural properties of propolis and further evaluated past studies that investigated propolis as an alternative product for the treatment of COVID-19 symptoms. In addition, the review also highlights the possible mode of propolis action as well as molecular simulations of propolis compounds that may interact with the SARS-CoV-2 virus. The activity of propolis compounds in decreasing the impact of COVID-19-related comorbidities, the possible roles of such compounds as COVID-19 vaccine adjuvants, and the use of nutraceuticals in COVID-19 treatment, instead of pharmaceuticals, has also been discussed.

Propolis Contra Pharmacological Interventions in Bees

In addition to wax, propolis is a mixture of resins, terpenes, and etheric and aromatic oils. This composition supports its very strong biochemical activity that affects bee health. Bee colonies are externally exposed to the activity of other different pharmacologically active substances and toxic agents used in beekeeping procedures, veterinary interventions, and the environment. Even if free form common diseases, they may suffer from parasites or toxins. In any such case the abundance and variety of honeyflow, besides proper therapy, is crucial for the maintenance of bee health. Propolis itself cannot be considered as food but can be considered as micro-nutrients for bees. This is due to the fact that some of its compounds may penetrate different bee products, and this way be consumed by bees and their larvae, while stored in the hive. This perspective shows propolis as natural agent reducing the toxicity of pyrethroid acaricides, stimulating production of detoxification enzymes, enhancing the action of antibiotics, and increasing expression of genes that encode proteins responsible for detoxication. The aim of this review is to summarize current data on the possible impact on veterinary public health of the introduction into propolis of residues of pharmacological agents approved in the EU for use in the treatment of bee colonies and their environment.

Chemical Profiling, Antioxidant, and Antimicrobial Activity of Saudi Propolis Collected by Arabian Honey Bee (Apis mellifera jemenitica) Colonies

Propolis (bee glue) is a complex, phyto-based resinous material obtained from beehives. Its chemical and biological properties vary with respect to bee species, type of plants, geographical location, and climate of a particular area. This study was planned with the aim of determining the chemical composition and to investigate various properties (against oxidants and microbes) of different extracts of Saudi propolis collected from Arabian honey bee (Apis mellifera jemenitica) colonies headed by young queens. Chemical analysis of propolis extracts with different solvents, i.e., ethyl acetate (Eac), methanol (Met), butanol (BuT), and hexane (Hex) was done through colorimetry for the total phenolic content (TPC) and total flavonoid content (TFC) evaluation. For separation and extensive characterization of the Met extract, chromatography and 1H NMR were deployed. Six different microorganisms were selected to analyze the Saudi-propolis-based extract’s antimicrobial nature by measuring zones of inhibition (ZOI) and minimum inhibitory concentration (MIC). Molecular docking was done by utilizing AutodDock, and sketching of ligands was performed through Marvin Chem Sketch (MCS), and the resultant data after 2D and 3D clean were stored in .mol format. The highest TFC (96.65 mg quercetin equivalents (QE)/g of propolis) and TPC (325 mg gallic acid equivalents (GAE)/g of propolis) were noted for Met. Six familiar compounds were isolated, and recognition was done with NMR. Met extract showed the greatest 1,1-diphenyl-2-picrylhydrazyl radical (DPPH) free radical scavenging activity and Ferric Reducing Antioxidant Power (FRAP). Met showed max microbial activity against Staphylococcus aureus (ZOI = 18.67 mm, MIC = 0.625 mg/mL), whereas the minimum was observed in Hex against E. coli (ZOI = 6.33 mm, MIC = 2.50 mg/mL). Furthermore, the molecular docking process established the biological activity of separated compounds against HCK (Hematopoietic cell kinase) and Gyrase B of S. aureus. Moreover, the stability of protein–ligand complexes was further established through molecular dynamic simulation studies, which showed that the receptor–ligand complexes were quite stable. Results of this research will pave the way for further consolidated analysis of propolis obtained from Arabian honey bees (A. m. jemenitica).

Antimicrobial activity of volatile oils from Brazilian stingless bees Melipona quadrifasciata quadrifasciata and Tetragonisca angustula propolis

Few studies were performed on the volatile components' properties of propolis from native Brazilian stingless bees. This work sought to extract, chemically characterize, and evaluate of the antimicrobial properties of volatile oils from propolis of the stingless bees Melipona quadrifasciata quadrifasciata (MQ) and Tetragonisca angustula (TA). The volatile oils from the pulverized propolis samples were obtained in a Clevenger apparatus and characterized by gas chromatography coupled to mass spectrometry (GC-MS) and to flame ionization detector (GC-FID). All samples showed promising activity against Mycoplasma pneumoniae , with MICs from 103 to 224 µg mL -1 , nonetheless, they were less active against cell walled bacteria. Activity against Candida species was moderate, but one MQ sample showed a MIC value of 103 µg mL -1 against C. tropicallis . Oils' fractionation showed no improvement in antibacterial activity. The promising antibacterial effect against this microorganism is likely related to the synergism between the components of the volatile oils.

Application of Nanocomposites from Bees Products and Nano-Selenium in Edible Coating for Catfish Fillets Biopreservation

Bee products, e.g., chitosan and propolis (Pro), have extraordinary importance in many disciplines including food biopreservation. Fish meat is highly susceptible to vast spoilage, especially catfish (Clarias gariepinus) products. The current work involved the extraction of bees’ chitosan nanoparticles (BCht), Pro, Pro-mediated SeNPs and their composites, to evaluate them as potential antimicrobial and preservative nano-compounds, for the preservation of catfish fillets and augment their quality. BCht was extracted from bees (Apis mellifera) corpses and had a 151.9 nm mean particle diameter. The Pro was used for biosynthesis of SeNPs, which had 11.2 nm mean diameters. The entire compounds/composites exhibited powerful antibacterial acts against Escherichia coli, Staphylococcus aureus and Salmonella typhimurium, where S aureus had the uppermost resistance. BCht/Pro/SeNPs were the most forceful toward all bacterial strains. The constructed edible coatings (ECs) from produced compounds/composites (BCht, Pro, Pro/SeNPs, Pro/BCht and BCht/Pro/SeNPs) had elevated efficiency for preserving catfish fillets during cold storages for 7 days. The microbiological (total counts, psychrophilic bacteria, yeast and molds), spoilage chemical parameters (TVB-N, TBARS) and sensorial attributes (appearance, odor, color, overall quality) of ECs-treated fillets indicated the nanocomposite’s efficiency for protecting the fish from microbial growth, the progress of chemical spoilage indicators and maintaining the sensorial quality of treated stored fillets. The most effective nanocomposite for maintaining the entire fillet’s quality was the BCht/Pro/SeNP. The based ECs on BNCt, Pro/SeNPs and their nanocomposites could be endorsed for prospective employment in the biopreservation of various seafoods.

A study of the antibacterial mechanism of pinocembrin against multidrug-resistant Aeromonas hydrophila

Aeromonas hydrophila is a common pathogen in fish that has caused severe economic losses in aquaculture worldwide. With the emergence of bacterial resistance, it is necessary to develop new drugs to combat bacterial infection, particularly for multidrug-resistant bacteria. In this study, the antibacterial activity of pinocembrin was investigated by observing bacterial growth and microscopic structure, and its mechanism of action was identified by investigating its effect on protein and DNA. The antibacterial susceptibility test indicated that pinocembrin inhibits A. hydrophila growth. The minimal inhibitory concentration and minimum bactericidal concentration were 256 μg/mL and 512 μg/mL, respectively. Ultrastructurally, the bacteria treated with pinocembrin showed surface roughness and plasmolysis. When bacteria were treated with 512 μg/mL pinocembrin, lactate dehydrogenase activity and soluble protein content decreased significantly, and electrical conductivity and DNA exosmosis levels increased by 4.21 ± 0.64% and 15.98 ± 1.93 mg/L, respectively. Staining with 4', 6-Diamidino-2-phenylindole showed that the nucleic acid fluorescence intensity and density decreased after the treatment with pinocembrin. Pinocembrin may inhibit the growth of A. hydrophila by increasing cell membrane permeability and affecting protein and DNA metabolism. Thus, pinocembrin is a candidate drug for the treatment of A. hydrophila infection in aquaculture.

Propolis characterization and antimicrobial activities against Staphylococcus aureus and Candida albicans: A review

Propolis is a plant-based sticky substance that is produced by honeybees. It has been used traditionally by ancient civilizations as a folk medicine, and is known to have many pharmaceutical properties including antioxidant, antibacterial, antifungal, anti-inflammatory, antiviral, and antitumour effects. Worldwide, researchers are still studying the complex composition of propolis to unveil its biological potential, and especially its antimicrobial activity against a variety of multidrug-resistant microorganisms. This review explores scientific reports published during the last decade on the characterization of different types of propolis, and evaluates their antimicrobial activities against Staphylococcus aureus and Candida albicans. Propolis can be divided into different types depending on their chemical composition and physical properties associated with geographic origin and plant sources. Flavonoids, phenols, diterpenes, and aliphatic compounds are the main chemicals that characterize the different types of propolis (Poplar, Brazilian, and Mediterranean), and are responsible for their antimicrobial activity. The extracts of most types of propolis showed greater antibacterial activity against Gram-positive bacteria: particularly on S. aureus, as well as on C. albicans, as compared to Gram-negative pathogens. Propolis acts either by directly interacting with the microbial cells or by stimulating the immune system of the host cells. Some studies have suggested that structural damage to the microorganisms is a possible mechanism by which propolis exhibits its antimicrobial activity. However, the mechanism of action of propolis is still unclear, due to the synergistic interaction of the ingredients of propolis, and this natural substance has multi-target activity in the cell. The broad-spectrum biological potentials of propolis present it as an ideal candidate for the development of new, potent, and cost-effective antimicrobial agents.

Antibacterial Activity of Chinese Red Propolis against Staphylococcus aureus and MRSA

The antibacterial activity of propolis has long been of great interest, and the chemical composition of propolis is directly dependent on its source. We recently obtained a type of propolis from China with a red color. Firstly, the antibacterial properties of this unusual propolis were determined against Staphylococcus aureus and methicillin-resistant Staphylococcus aureus (MRSA). Studies on its composition identified and quantified 14 main polyphenols of Chinese red propolis extracts (RPE); quantification was carried out using liquid chromatography triple quadrupole tandem mass spectrometry (LC-QQQ-MS/MS) and RPE was found to be rich in pinobanksin, pinobanksin-3-acetate, and chrysin. In vitro investigations of its antibacterial activity revealed that its activity against S. aureus and MRSA is due to disruption of the cell wall and cell membrane, which then inhibits bacterial growth. Despite its similar antibacterial activities against S. aureus and MRSA, metabolomic analysis further revealed the effects of RPE on bacteria metabolism were different. The untargeted metabolomic results showed that a total of 7 metabolites in 12 metabolic pathways had significant changes (Fold change > 2, p < 0.05 *) after RPE treatment in S. aureus, while 11 metabolites in 9 metabolic pathways had significant changes (Fold change > 2, p < 0.05 *) after RPE treated on MRSA. Furthermore, RPE downregulated several specific genes related to bacterial biofilm formation, autolysis, cell wall synthesis, and bacterial virulence in MRSA. In conclusion, the data obtained indicate that RPE may be a promising therapeutic agent against S. aureus and MRSA.

Chemical Variability and Pharmacological Potential of Propolis as a Source for the Development of New Pharmaceutical Products

This review aims to analyze propolis as a potential raw material for the development and manufacture of new health-promoting products. Many scientific publications were retrieved from the Scopus, PubMed, and Google Scholar databases via searching the word "propolis". The different extraction procedures, key biologically active compounds, biological properties, and therapeutic potential of propolis were analyzed. It was concluded that propolis possesses a variety of biological properties because of a very complex chemical composition that mainly depends on the plant species visited by bees and species of bees. Numerous studies found versatile pharmacological activities of propolis: antimicrobial, antifungal, antiviral, antioxidant, anticancer, anti-inflammatory, immunomodulatory, etc. In this review, the composition and biological activities of propolis are presented from a point of view of the origin and standardization of propolis for the purpose of the development of new pharmaceutical products on its base. It was revealed that some types of propolis, especially European propolis, contain flavonoids and phenolic acids, which could be markers for the standardization and quality evaluation of propolis and its preparations. One more focus of this paper was the overview of microorganisms’ sensitivity to propolis for further development of antimicrobial and antioxidant products for the treatment of various infectious diseases with an emphasis on the illnesses of the oral cavity. It was established that the antimicrobial activity of different types of propolis is quite significant, especially to Gram-negative bacteria and lipophilic viruses. The present study could be also of interest to the pharmaceutical industry as a review for the appropriate design of standardized propolis preparations such as mouthwashes, toothpastes, oral drops, sprays, creams, ointments, suppositories, tablets, and capsules, etc. Moreover, propolis could be regarded as a source for the isolation of biologically active substances. Furthermore, this review can facilitate partially overcoming the problem of the standardization of propolis preparations, which is a principal obstacle to the broader use of propolis in the pharmaceutical industry. Finally, this study could be of interest in the area of the food industry for the development of nutritionally well-balanced products. The results of this review indicate that propolis deserves to be better studied for its promising therapeutic effects from the point of view of the connection of its chemical composition with the locality of its collection, vegetation, appropriate extraction methods, and standardization.

Monitoring of Hazelnut oil quality during thermal processing in comparison with extra virgin olive oil by using ATR-FTIR spectroscopy combined with chemometrics

Hazelnut oil (HO), which is not widely used because its healthy properties are not fully known yet, is an excellent nutrient due to its high content of monounsaturated fatty acids and antioxidants. In this study, the effects of thermal processing on the quality of HO in comparison to extra virgin olive oil (EVOO), which is one of the healthiest and heat-resistant oils, were investigated using Attenuated Total Reflection-Fourier Transform Infrared (ATR-FTIR) spectroscopy. Oil samples were heated at a frying temperature (180 °C) for 24 h in periods of 8 h per day and alterations in the spectra of these oils sampled every 2 h were evaluated. The heating process caused decreases in the areas of the bands at 3007 and 722 cm^-1 and the area ratios of 3007/2854 and 722/2854 cm^-1 and increases in the areas of the bands at 987 and 965 cm^-1 and the area ratio of 965/2854 cm^-1 in both oils suggesting the conjugation and cis-trans isomerization of unsaturated fatty acids. In addition, heating caused increases in the areas of the bands at 3475 and 1744 cm^-1 and the ratios of 3475/2854 cm^-1 and 1744/2854 cm^-1, a shift to a lower value in the wavenumber and a broadening of the 1744 cm^-1 band indicating the formation of primary and secondary oxidation products in the heated oils, which were also supported by chemical studies. Most of these changes began earlier in EVOO and all occurred to a higher extent, revealing that HO has a higher thermal stability than EVOO. Principal component analysis and hierarchical cluster analysis confirmed that HO is more resistant to heat than EVOO. These results showed that HO is superior to EVOO and it could be used for frying as a healthier and cheaper oil alternative. This study also indicated that oil oxidation could be monitored easily and rapidly via ATR-FTIR spectroscopy.

Propolin G-Suppressed Epithelial-to-Mesenchymal Transition in Triple-Negative Breast Cancer Cells via Glycogen Synthase Kinase 3β-Mediated Snail and HDAC6-Regulated Vimentin Degradation

Triple-negative breast cancer (TNBC) is a highly aggressive breast cancer with a poor prognosis. The incidence and mortality rate of TNBC are frequently found in younger women. Due to the absence of a good therapeutic strategy, effective remedies for inhibiting TNBC have been developed for improving the cure rate. Epithelial-to-mesenchymal transition (EMT) is a critical mechanism to regulate cancer cell motility and invasion. Furthermore, ectopic expression of EMT molecules correlates with the metastasis and poor prognosis of TNBC. Targeting EMT might be a strategy for the therapy and prevention of TNBC. Propolin G, an active c-prenylflavanone in Taiwanese propolis, has been shown to possess anti-cancer activity in many cancers. However, the anti-metastasis activity of propolin G on TNBC is still unclear. The present study showed that the migration and invasion activities of TNBC cells was suppressed by propolin G. Down-regulated expression of Snail and vimentin and up-regulated expression of E-cadherin were dose- and time-dependently observed in propolin G-treated MDA-MB-231 cells. Propolin G inhibited Snail and vimentin expressions via the signaling pathways associated with post-translational modification. The activation of glycogen synthase kinase 3β (GSK-3β) by propolin G resulted in increasing GSK-3β interaction with Snail. Consequently, the nuclear localization and stability of Snail was disrupted resulting in promoting the degradation. Propolin G-inhibited Snail expression and the activities of migration and invasion were reversed by GSK-3β inhibitor pretreatment. Meanwhile, the outcomes also revealed that histone deacetylase 6 (HDAC6) activity was dose-dependently suppressed by propolin G. Correspondently, the amounts of acetyl-α-tubulin, a down-stream substrate of HDAC6, were increased. Dissociation of HDAC6/Hsp90 with vimentin leading to increased vimentin acetylation and degradation was perceived in the cells with the addition of propolin G. Moreover, up-regulated expression of acetyl-α-tubulin by propolin G was attenuated by HDAC6 overexpression. On the contrary, down-regulated expression of vimentin, cell migration and invasion by propolin G were overturned by HDAC6 overexpression. Conclusively, restraint cell migration and invasion of TNBC by propolin G were activated by the expression of GSK-3β-suppressed Snail and the interruption of HDAC6-mediated vimentin protein stability. Aiming at EMT, propolin G might be a potential candidate for TNBC therapy.

Bio-based and bio-inspired adhesives from animals and plants for biomedical applications

With the "many-headed" slime mold Physarum polycelphalum having been voted the unicellular organism of the year 2021 by the German Society of Protozoology, we are reminded that a large part of nature's huge variety of life forms is easily overlooked - both by the general public and researchers alike. Indeed, whereas several animals such as mussels or spiders have already inspired many scientists to create novel materials with glue-like properties, there is much more to discover in the flora and fauna. Here, we provide an overview of naturally occurring slimy substances with adhesive properties and categorize them in terms of the main chemical motifs that convey their stickiness, i.e., carbohydrate-, protein-, and glycoprotein-based biological glues. Furthermore, we highlight selected recent developments in the area of material design and functionalization that aim at making use of such biological compounds for novel applications in medicine - either by conjugating adhesive motifs found in nature to biological or synthetic macromolecules or by synthetically creating (multi-)functional materials, which combine adhesive properties with additional, problem-specific (and sometimes tunable) features.

Propolis: chemical diversity and challenges in quality control

Propolis is a resinous natural product produced by honeybees using beeswax and plant exudates. The chemical composition of propolis is highly complex, and varies with region and season. This inherent chemical variability presents several challenges to its standardisation and quality control. The present review was aimed at highlighting marker compounds for different types of propolis, produced by the species Apis mellifera, from different geographical origins and that display different biological activities, and to discuss strategies for quality control. Over 800 compounds have been reported in the different propolises such as temperate, tropical, birch, Mediterranean, and Pacific propolis; these mainly include alcohols, acids and their esters, benzofuranes, benzopyranes, chalcones, flavonoids and their esters, glycosides (flavonoid and diterpene), glycerol and its esters, lignans, phenylpropanoids, steroids, terpenes and terpenoids. Among these, flavonoids (> 140), terpenes and terpenoids (> 160) were major components. A broad range of biological activities, such as anti-oxidant, antimicrobial, anti-inflammatory, immunomodulatory, and anticancer activities, have been ascribed to propolis constituents, as well as the potential of these compounds to be biomarkers. Several analytical techniques, including non-separation and separation methods have been described in the literature for the quality control assessment of propolis. Mass spectrometry coupled with separation methods, followed by chemometric analysis of the data, was found to be a valuable tool for the profiling and classification of propolis samples, including (bio)marker identification. Due to the rampant chemotypic variability, a multiple-marker assessment strategy considering geographical and biological activity marker(s) with chemometric analysis may be a promising approach for propolis quality assessment.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s11101-022-09816-1.

Emerging Roles of Myeloid-Derived Suppressor Cells in Diabetes

Diabetes is a syndrome characterized by hyperglycemia with or without insulin resistance. Its etiology is attributed to the combined action of genes, environment and immune cells. Myeloid-derived suppressor cell (MDSC) is a heterogeneous population of immature cells with immunosuppressive ability. In recent years, different studies have debated the quantity, activity changes and roles of MDSC in the diabetic microenvironment. However, the emerging roles of MDSC have not been fully documented with regard to their interactions with diabetes. Here, the manifestations of MDSC and their subsets are reviewed with regard to the incidence of diabetes and diabetic complications. The possible drugs targeting MDSC are discussed with regard to their potential of treating diabetes. We believe that understanding MDSC will offer opportunities to explain pathological characteristics of different diabetes. MDSC also will be used for personalized immunotherapy of diabetes.

Analysis of bioactive compounds and chemical composition of Malaysian stingless bee propolis water extracts

Propolis is a resinous substance collected by stingless bees containing bioactive compounds which exert various biological properties. The present study focused on the evaluation of chemical profiles produced by three Indo-Malayan stingless bee propolis extracted using water. Fresh propolis was collected from the same area and ecosystem conditions in Selangor, Malaysia, namely Tetrigona apicalis, Tetrigona binghami, and Heterotrigona fimbriata. The bioactive compounds and chemical composition of propolis extracts were then analyzed using gas chromatography–mass spectrometry (GC–MS). Results showed that propolis from the three different stingless bee species consisted of major groups such as sugar (31.4%), carboxylic acid (17.1%), terpenoid (14.3%), sugar alcohol (11.4%), hydrocarbon (5.7%), aldehyde (5.7%) amino acid (2.9%) and other constituents (11.4%). Heterotrigona fimbriata displayed the highest amount for both total phenolics (13.21 mg/mL) and flavonoids (34.53 mg/mL) compared to other propolis extracts. There is also no significant difference detected between all samples since p ≤ 0.05. In conclusion, this study shows that Malaysian stingless bee propolis contain bioactive components that have great potential to be used for their therapeutic and medicinal benefits. However, more investigations and analysis of stingless bee propolis need to be carried out in order to enhance the understanding and applications of propolis in the future.

Antifungal Effects of Iranian Propolis Extract and Royal jelly Against Candida albicans In-Vitro

BACKGROUND

Candida albicans is the most important opportunistic fungal that can establish infection in susceptible individuals. Iranian Propolis and Royal jelly are bee products that are traditionally used against fungal infections. This study was aimed to evaluate the antifungal effects of Iranian Propolis extract and Royal jelly against C. albicans in vitro.

METHODS

Antifungal activities of the extracts were performed according to microbroth dilution method in 96-well microdilution plates. The amount of minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) based on counting the number of fungal colonies (CFU) were evaluated for each of Royal jelly and Iranian Propolis extracts against C. albicans compared with the control group.

RESULTS

In this study, the MIC, MIC₅₀, and MFC of Royal jelly on C. albicans were, respectively, 80, 103 ± 25, and 160 ± 34 mg/mL and for the Iranian Propolis alcoholic extract were, respectively, 0.030 ± 0.015, 0.0618 ± 0.027, and 0.0833 ± 0.0599 mg/mL.

CONCLUSIONS

The results indicate that both Royal jelly and Iranian Propolis alcoholic extract are effective against C. albicans, but the former species has higher antifungal activity. If the clinical trials confirm the results of this study, Iranian propolis, as a new antifungal agent by replacing chemical drugs, can be used to develop antifungal medicinal herbs.

Propolis - quality analysis and use in topical formulations

The aim of this study was to produce propolis extracts, assess their quality and effect on skin cells and determine the penetration of active ingredients from designed semi-solid topical formulations. The use of higher-concentration ethanol and a larger amount of raw material allows extracting a larger quantity of active ingredients from raw propolis. Ultrasound extraction is an effective method for the production of aqueous extracts of propolis. The results show that depending on concentration, propolis extracts reduce the viability of keratinocytes. The phenolic compounds under observation penetrated the epidermis and dermis from designed formulations. The base of semi-solid formulation influences the efficacy of propolis preparations. The overall quantity of phenolic compounds that penetrated the skin was around 2 % from the ointment and 1.5 % from the cream.

Processing Technologies for Bee Products: An Overview of Recent Developments and Perspectives

Increased demand for a more balanced, healthy, and safe diet has accelerated studies on natural bee products (including honey, bee bread, bee collected pollen royal jelly, propolis, beeswax, and bee venom) over the past decade. Advanced food processing techniques, such as ultrasonication and microwave and infrared (IR) irradiation, either has gained popularity as alternatives or combined with conventional processing techniques for diverse applications in apiculture products at laboratory or industrial scale. The processing techniques used for each bee products have comprehensively summarized in this review, including drying (traditional drying, infrared drying, microwave-assisted traditional drying or vacuum drying, and low temperature high velocity-assisted fluidized bed drying), storage, extraction, isolation, and identification; the assessment methods related to the quality control of bee products are also fully mentioned. The different processing techniques applied in bee products aim to provide more healthy active ingredients largely and effectively. Furthermore, improved the product quality with a shorter processing time and reduced operational cost are achieved using conventional or emerging processing techniques. This review will increase the positive ratings of the combined new processing techniques according to the needs of the bee products. The importance of the models for process optimization on a large scale is also emphasized in the future.

An insight into the botanical origins of propolis from permanent preservation and reforestation areas of southern Brazil

Brown propolis from permanent preservation and reforestation areas of southern Brazil have attracted international commercial interest and have a unique composition, although little is known about their botanical origins, which are the plant resins used by bee foragers to produce propolis. Hence, the volatile profiles of organic and non-organic brown propolis and resins of suspected botanical origins—Araucaria angustifolia, Pinus elliott and Pinus taeda—were determined using static headspace gas chromatography coupled to mass spectrometry (SHS-GCMS) and compared. Nighty nine volatiles were tentatively identified, and monoterpenes and sesquiterpenes were the most abundant classes. Principal component analysis (PCA) showed similarity between organic propolis and A. angustifolia volatile profiles (p < 0.05). Hierarchical clustering analysis showed singularities among propolis, even between propolis produced 1 km away from each other. Heatmaps were used to identify peaks present in similar relative intensities in both propolis and conifer resins. Hence, the approach using volatile profiles shed light to propolis botanical origins, which is important for authentication and traceability purposes.