Investigation of antioxidant capacity, bioaccessibility and LC-MS/MS phenolic profile of Turkish propolis

Carbohydrate-based co-encapsulation of spice oleoresin blends: Impact on flavor release profiles, storage stability, and sensory acceptance

The study highlights the impact of different carbohydrate-based wall materials on the encapsulation and release of flavors and physicochemical characteristics of spray-dried oleoresin blends. The inlet temperature and the wall material type significantly affected the spray drying yield, and Hi-Cap 100, at 150 °C, produced the highest yield. All the wall materials had high water solubility, and Hi-Cap 100 reported the best wettability. Gum Arabic denoted the highest encapsulation efficiency (77.3 ± 0.6%) and the best encapsulation capacity of pungent compounds, phytochemicals, and colors, being approximately two-fold higher than Hi-Cap 100. The blend of gum Arabic and Hi-Cap 100 produced the most efficient volatile release (31 compounds). Thermal treatments accelerated the release of pungent and aroma compounds, while 2% salt concentration delivered the maximum flavor release. Encapsulation retained more than 85% of compounds during 3 months of storage, and thus, the findings suggest industrial applications of encapsulated oleoresin powders would be favorable.

Liposomal propolis loaded xanthan gum-salep hydrogels: Preparation, characterization, and in vitro bioaccessibility of phenolics

Liposomes are gaining interest in food and pharmaceutical applications due to their biocompatibility and non-toxicity. However, they suffer from low colloidal stability, leakage of encapsulated substances, and poor resistance to intestinal digestive conditions. To address these issues, propolis extract (PE) was encapsulated within a hybrid system combining liposomes and hydrogels. PE encapsulated in phosphatidylcholine liposome formulations incorporated with two different food additives: polyethylene sorbitan monooleate (T80) and ammonium phosphatide (AMP) was embedded in xanthan gum-salep hydrogels. The embedded liposomes protected their structure and did not change the flow behaviour of the hydrogels. AMP-liposomal gels exhibited a stronger solid character. The mucoadhesiveness of liposomal gels was mostly governed by the higher xanthan gum ratio, while PE loading also yielded higher mucoadhesiveness. The bioaccessibility (BI%) of the phenolic compounds ranged from 10.13 to 582.75 % in the liposomal gel. The proposed hybrid encapsulation method not only provided enhanced solubility to hydrophobic PE but also protected its phenolic compounds against simulated digestion conditions. Moreover, converting aqueous liposomes into gel structures would also expand their application range in various functional food formulations.

Therapeutic Potential of Propolis and Royal Jelly in Encephalitozoon Intestinalis Infection: An in Vitro Study

PURPOSE

Encephalitozoon intestinalis is an obligate intracellular microsporidian fungus that causes severe gastrointestinal infections, particularly in immunocompromised individuals. Propolis (PROP), a resinous substance derived from bees, has antimicrobial, anti-inflammatory and antioxidant properties, while royal jelly (RJ) has immunomodulatory, antioxidant and antimicrobial activities. The aim of this study was to investigate the therapeutic potential of PROP and RJ against E. intestinalis.

METHODS

The phenolic composition of PROP was analysed by high-performance liquid chromatography with diode array detection, and the chemical components of RJ were evaluated according to ISO12824 standards. The cytotoxicity of PROP and RJ on HEK-293 cells was evaluated using the XTT assay. The three highest non-cytotoxic concentrations of each sample were tested for their effects on E. intestinalis spores by qRT-PCR. Trichrome-stained photomicrographs were used to assess spore density in HEK-293 cells treated with PROP and RJ.

RESULTS

PROP analysis revealed flavonoids such as quercetin, kaempferol, pinocembrin and galangin, as well as phenolic acids such as caffeic and cinnamic acids, known for their bioactive properties. RJ contained mainly proteins, lipids, carbohydrates and sugars, reflecting its role as a nutritionally and biologically active substance. According to the results of this first study evaluating the effect of PROP and RJ on E. intestinalis, all concentrations evaluated in the study showed a significant inhibitory effect on the growth of E. intestinalis spores compared to the control group.

CONCLUSION

In conclusion, we believe that PROP and RJ should be considered as an alternative option in the development of antimicrosporidial drugs due to their potential medicinal and pharmaceutical properties.

Paper-Based Device for Phenolic Content Determination in Tea Extracts

INTRODUCTION

Phenolic compounds garner interest in developing medicines, nutraceuticals, and cosmeceuticals based on natural products. The quantity of phenolic compounds in a sample is commonly determined via spectrophotometry; however, this instrumented technique is relatively laborious and time consuming and requires a large amount of reagents.

OBJECTIVE

This work aimed to develop a simple, point-of-need colorimetric sensor to rapidly determine total phenolic content (TPC) in tea extracts.

METHODOLOGY

We developed a radial paper-based analytical device (PAD) for TPC determination based on the established colorimetric reaction between the Folin-Ciocâlteu reagent and phenols. The PAD was designed to enable quantitative (with image capturing device and color processing software) and semiquantitative (using a color palette reference card) determinations. Analytical performance and stability of the PAD were evaluated based on the color responses.

RESULTS

The PAD was successfully applied for the determination of phenolics in tea extracts obtained using several polar protic solvents, including water, methanol, and ethanol, with satisfactory accuracy (recovery of 95.5%-104%, 110%-116%, and 104%-110%, respectively) and precision (RSD < 9%). The obtained TPC values also agreed with those from visible spectrophotometry. Semiquantitative determination using the color reference card with three categories of TPC level (i.e., 0-100, 100-500, and 500-1000 mg gallic acid equivalent/L) provided > 95% accuracy. The devices were the most stable when stored at 4°C in a light-protected, vacuum-sealed container. The proposed PAD is promising for simple, rapid (~10-20 min), and accurate estimation of TPC in plant extracts.

The Influence of Geographical Origin on Poplar Propolis Composition and the Impact of Human Microbiota

Ethanol extracts obtained from 13 poplar propolis samples originating from various European countries by traditional maceration were tested for total polyphenols, flavonoid content, and antioxidant activity. Moreover, the content of 18 polyphenolic compounds (from the group of phenolic acids and flavonoids) was determined using the HPLC method. The inhibitory effect of six selected extracts with the highest activity was assessed by well-diffusion method against five strains (Bifidobacterium spp., L. rhamnosus, L. acidophilus, E. coli, and Bacteroides spp.) of intestinal bacteria self-isolated from the faeces of obese probands with the use of selective media. It was found that the antioxidant activity of propolis varied depending on geographical origin and even among samples from the same region, which indicates that some other factors also influence propolis quality. The samples of different geographical origin varied mainly in the share of individual phenolic compounds, and it was not possible to find a characteristic marker of origin, excluding the galangin present in the Polish samples only. Assessing the inhibitory activity of propolis (in the range of 70 mg to 10 µg per mL) indicated that the concentration of 100 µg/mL was found as being safe for tested fecal bacteria (Bifidobacterium spp., L. rhamnosus, L. acidophilus, E. coli, and Bacteroides spp.). As no negative effect of low doses of propolis on the intestinal microflora was found, it can be suggested that its use in recommended doses brings only beneficial effects to the body.

Phenolic Composition, Antiradical, Antimicrobial, and Anti-Inflammatory Activities of Propolis Extracts from North East Spain

Antioxidant-related parameters and anti-inflammatory and antimicrobial activities against Listeria monocytogenes were assessed in eight North East Spain poplar propolis samples. Propolis extracts (PEs) were obtained using 70% ethanol (PEE) and methanol (PME). Yield and total phenol compounds were higher in PEE. Phenolic acids were analyzed by a high-performance liquid chromatograph-diode array detector. Caffeic and ferulic acids were quantified in all PEE and PME. All samples contained p-coumaric acid (quantified in 6 PEE and in 3 PME). Ascorbic acid was detected in all propolis, but mainly quantified in PME (≤0.37 mg/g PE). Biological properties were tested on PEE. As for antiradical activities, trolox equivalent antioxidant capacity (TEAC) [against 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)•+], ranged between 578 and 4620 µmol trolox/g, 2,2-diphenyl-1-picrylhydrazyl (DPPH) (against DPPH free radical), between 0.049 and 0.094 mg/mL, antioxidant activity against hydroxyl (•OH) radical (AOA), between 0.04 and 11.01 mmol uric acid/g, and oxygen radical absorbance capacity (ORAC) against peroxyl (ROO•) radical between 122 and 3282 µmol trolox/g. Results of TEAC, AOA, and ORAC were significantly correlated. IC50 anti-inflammatory activity ranged from 1.08 to 6.19 mg/mL. Propolis showed higher inhibitory activity against L. monocytogenes CECT934 and L. monocytogenes CP101 by agar well diffusion (P < .05) (10.5 and 10.2 mm, respectively) than against L. monocytogenes CP102 (7.0 mm). Data of this research show that North East Spain propolis may be of interest for pharmaceutical and food industry use.

The evaluation of L-arginine solution as a solvent for propolis extraction: The phenolic profile, antioxidant, antibacterial activity, and in vitro bioaccessibility

Ethanol has been widely used for the extraction of propolis. Due to its certain disadvantages, there has been an ongoing search to find alternative non-ethanolic extraction solvents. This study aimed to compare the phenolics, antioxidant, and antibacterial activity of propolis extracts prepared with 70% ethanol (EWE), propylene glycol (PGE), and L-arginine solution (BE). All extracts were subjected to an in vitro simulated digestion procedure, and the phenolic profile of non-digested and digested samples was determined by using LC-MS/MS. Additionally, the change in total phenolic (TPC), total flavonoid content (TFC), and antioxidant capacities were determined at each digestion phase. TPC and TFC of non-digested propolis extracts had similar values, although BE showed higher antioxidant capacity (p < .05). The amount of TPC reached or transformed at the intestinal stage was higher for BE and PG compared to EWE. BE also provided the highest antioxidant capacity assay in digested samples. The most common phenolics were pinocembrin, pinobanskin, galangin, and CAPE in non-digested extracts. However, their concentration was drastically reduced by digestion, and their recovery (R%) ranged from 0% to 9.38% of the initial amount detected in the non-digested extracts. Chrysin was the most bioaccessible flavonoid in all extracts. Among phenolic acids, the highest R% was determined for trans-cinnamic acid (22.14%) from BE. All extracts showed in vitro inhibitory activity against Escherichia coli and Staphylococcus aureus. This study suggests that an L-arginine solution could be used as an alternative solvent to ethanol and propylene glycol for propolis extraction.

Stability, Content of Bioactive Compounds and Antioxidant Activity of Emulsions with Propolis Extracts during Simulated In Vitro Digestion

The objective in this work was the evaluation of the stability and content of bioactive compounds (total phenols and total flavonoids) and antioxidant activity of emulsions of ethanolic extracts of propolis obtained by ultrasound, during simulated in vitro digestion. The emulsions prepared with propolis extracts were evaluated on certain properties: their emulsion efficiency, stability (zeta potential, particle size, electrical conductivity), content of bioactive compound (total phenolics and total flavonoids), antioxidant activity and their behavior during simulated in vitro digestion. Based on the total phenol content, an emulsification efficiency of 87.8 ± 1.9% to 97.8 ± 3.8% was obtained. The particle size of the emulsions was 322.5 ± 15.33 nm to 463.9 ± 33.65 nm, with a zeta potential of -31.5 ± 0.66 mV to -28.2 ± 1.0 mV and electrical conductivity of 22.7 ± 1.96 µS/cm to 30.6 ± 0.91 µS/cm. These results indicate good emulsion stability. During simulated in vitro digestion, the content of bioactive compounds (total phenolics, total flavonoids) and antioxidant activity were affected during 77 days of storage at 4 °C. It was concluded that the emulsion process fulfills the function of protecting the bioactive compounds and therefore their biological activity.

Effect of wax separation on macro- and micro-elements, phenolic compounds, pesticide residues, and toxic elements in propolis

Propolis, a natural product with many biological activities, is a resinous material produced by honeybees. It contains not only valuable components but also some possible contaminants in varying amounts. Hence, this study aimed to examine how the process step of wax separation affects certain elements, pesticide residues, and phenolic compounds in propolis. Total phenolics, elements, and some pesticide residues were analyzed in the crude propolis (CP samples), wax portion (W samples), and remaining propolis fraction (PF samples) after wax separation. Total phenolics of the CP samples were determined in the range of 31.90-45.00 mg GAE g-1 sample, while those of the PF samples were in the range of 54.97-162.09 mg GAE g-1 sample. Loss/reduction values by means of wax separation for phenolics were calculated as 10.88% and 17.89%, respectively. Pb contents of all PF samples were low (0.232-1.520 mg kg-1), but it was also noteworthy that nearly 40% or even more of Cr, As, Cd, and Pb were removed by wax separation. Removal of significant amounts of carbendazim (38.09%-67.35%), metalaxyl (81.57%-72.67%), tebuconazole (65.99%-78.36%), and propargite (88.46%-83.05%) was also achieved. Wax separation enables the removal of toxic substances from crude propolis without causing huge losses in phenolic compounds.

Techno-functional properties of active film based on guar gum-propolis and its application for "Nanguo" pears preservation

Guar gum (GG) composite films, incorporating the ethanolic extract of propolis (EEP), were prepared and subjected to a comprehensive investigation of their functional characteristics. The addition of EEP resulted in a discernible enhancement in the opacity, moisture barrier capacity, and elongation at break. Incorporating EEP led to a noteworthy increase in the total phenolic and total flavonoid content of the films, resulting in superior antioxidant capacity upon GG-EEP films. Remarkably, the addition of 5 % EEP yielded noteworthy outcomes, manifesting in a DPPH radical scavenging rate of 47.60 % and the ABTS radical scavenging rate of 94.87 %, as well as FRAP and cupric reducing power of 331.98 mmol FeSO4-7H2O kg-1 and 56.95 μg TE mg-1, respectively. In addition, GG-EEP films demonstrated antifungal effect against Penicillium expansum and Aspergillus niger, along with a sustained antibacterial effect against Escherichia coli and Staphylococcus aureus. GG-EEP films had superior inhibitory ability against Gram-positive bacteria than Gram-negative bacteria. Crucially, GG-EEP composite films played a pivotal role in reducing both lesion diameter and depth, concurrently mitigating weight loss and firmness decline during the storage period of "Nanguo" pears. Therefore, GG-EEP composite films have the considerable potential to serve as advanced and effective active packaging materials for food preservation.

Potential Antidiabetic Activity of Apis mellifera Propolis Extraction Obtained with Ultrasound

Recent studies have linked phenolic compounds to the inhibition of digestive enzymes. Propolis extract is consumed or applied as a traditional treatment for some diseases. More than 500 chemical compounds have been identified in propolis composition worldwide. This research aimed to determine Mexican propolis extracts' total phenolic content, total flavonoid content, antioxidant activity, and digestive enzyme inhibitory activity (ɑ-amylase and ɑ-glucosidase). In vitro assays measured the possible effect on bioactive compounds after digestion. Four samples of propolis from different regions of the state of Oaxaca (Mexico) were tested (Eloxochitlán (PE), Teotitlán (PT), San Pedro (PSP), and San Jerónimo (PSJ)). Ethanol extractions were performed using ultrasound. The extract with the highest phenolic content was PE with 15,362.4 ± 225 mg GAE/100 g. Regarding the flavonoid content, the highest amount was found in PT with 8084.6 ± 19 mg QE/100 g. ABTS•+ and DPPH• radicals were evaluated. The extract with the best inhibition concentration was PE with 33,307.1 ± 567 mg ET/100 g. After simulated digestion, phenolics, flavonoids, and antioxidant activity decreased by 96%. In contrast, antidiabetic activity, quantified as inhibition of ɑ-amylase and ɑ-glucosidase, showed a mean decrease in enzyme activity of approximately 50% after the intestinal phase. Therefore, it is concluded that propolis extracts could be a natural alternative for treating diabetes, and it would be necessary to develop a protective mechanism to incorporate them into foods.

Caffeic Acid Phenethyl Ester (CAPE): Biosynthesis, Derivatives and Formulations with Neuroprotective Activities

Neurodegenerative disorders are characterized by a progressive process of degeneration and neuronal death, where oxidative stress and neuroinflammation are key factors that contribute to the progression of these diseases. Therefore, two major pathways involved in these pathologies have been proposed as relevant therapeutic targets: The nuclear transcription factor erythroid 2 (Nrf2), which responds to oxidative stress with cytoprotecting activity; and the nuclear factor NF-κB pathway, which is highly related to the neuroinflammatory process by promoting cytokine expression. Caffeic acid phenethyl ester (CAPE) is a phenylpropanoid naturally found in propolis that shows important biological activities, including neuroprotective activity by modulating the Nrf2 and NF-κB pathways, promoting antioxidant enzyme expression and inhibition of proinflammatory cytokine expression. Its simple chemical structure has inspired the synthesis of many derivatives, with aliphatic and/or aromatic moieties, some of which have improved the biological properties. Moreover, new drug delivery systems increase the bioavailability of these compounds in vivo, allowing its transcytosis through the blood-brain barrier, thus protecting brain cells from the increased inflammatory status associated to neurodegenerative and psychiatric disorders. This review summarizes the biosynthesis and chemical synthesis of CAPE derivatives, their miscellaneous activities, and relevant studies (from 2010 to 2023), addressing their neuroprotective activity in vitro and in vivo.

Phenolic Constituents, Antioxidant and Antimicrobial Activity and Clustering Analysis of Propolis Samples Based on PCA from Different Regions of Anatolia

This study aimed to evaluate the biochemical composition and biological activity of propolis samples from different regions of Türkiye to characterize and classify 24 Anatolian propolis samples according to their geographical origin. Chemometric techniques, namely, principal component analysis (PCA) and a hierarchical clustering algorithm (HCA), were applied for the first time to all data, including antioxidant capacity, individual phenolic constituents, and the antimicrobial activity of propolis to reveal the possible clustering of Anatolian propolis samples according to their geographical origin. As a result, the total phenolic content (TPC) of the propolis samples varied from 16.73 to 125.83 mg gallic acid equivalent per gram (GAE/g) sample, while the number of total flavonoids varied from 57.98 to 327.38 mg quercetin equivalent per gram (QE/g) sample. The identified constituents of propolis were phenolic/aromatic acids (chlorogenic acid, caffeic acid, p-coumaric acid, ferulic acid, and trans-cinnamic acid), phenolic aldehyde (vanillin), and flavonoids (pinocembrin, kaempferol, pinobanksin, and apigenin). This study has shown that the application of the PCA chemometric method to the biochemical composition and biological activity of propolis allows for the successful clustering of Anatolian propolis samples from different regions of Türkiye, except for samples from the Black Sea region.

Bioaccessibility of phenolic compounds using the standardized INFOGEST protocol: A narrative review

The INFOGEST protocol creation was a watershed for phenolic bioaccessibility studies. Because of this important initiative to standardize bioaccessibility studies, data comparisons between different laboratories are now expedited. It has been eight years since the INFOGEST protocol creation, and three from the latest update. However, the current status in terms of phenolic bioaccessibility and how far different laboratories are from reaching a consensus are still unrevealed. In this sense, this narrative review considered an evaluation of different studies that applied the INFOGEST protocol to investigate the bioaccessibility of phenolic compounds. The central objective was to compile the main findings and consensus and to identify possible gaps and future opportunities. This approach intends to further facilitate the use of this protocol by professionals in the field of food science and technology and related areas, generating a reflection on the actual level of standardization of the method. Despite the differences in phenolic compounds from diverse food matrices, and their peculiar behavior, some trends could be elucidated, in terms of phenolic release, stability, and/or transformation upon in vivo digestion. In contrast, there was no general consensus regarding sample preparation, how to report results and the form to calculate bioaccessibility, making it difficult to compare different studies. There is still a long road to effectively standardize the results obtained for phenolic bioaccessibility using the INFOGEST protocol, which is also an opportunity in terms of food analysis that can impact the food industry, especially for the development of nutraceuticals and functional foods.

Chemical characterization and antioxidant potential of ecuadorian propolis

The chemical composition and the antioxidant potential of Ecuadorian propolis samples (n = 19) collected in different provinces were investigated. HPLC-DAD-ESI/MSⁿ and GC-EI-MS analysis of the methanol extracts enabled us to define six types of Ecuadorian propolis based on their secondary metabolite composition. 68 compounds were identified, 59 of which are reported for the first time in Ecuadorian propolis. The detected compounds include flavonoids, diterpenes, triterpenes, organic acid derivatives, alkylresorcinol derivatives and nemorosone. Plants belonging to genera Populus, Mangifera and Clusia seemed to be vegetable sources employed by bees to produce Ecuadorian propolis. Total phenolic content and antioxidant activity of propolis extracts were determined by the Folin-Ciocalteu assay and 2,2-diphenyl-1-picrylhydrazyl and ferric reducing/antioxidant potential assays, respectively. As expected, the variable chemical composition affected the differences in terms of antioxidant potential.

Enhancement of the Antioxidant Capacity of Thyme and Chestnut Honey by Addition of Bee Products

Honey consumption and imports have increased in recent years, and it is considered by consumers to be a healthy alternative to more commonly used sweeteners. Honey contains a mixture of polyphenols and antioxidant compounds, and the botanical origin and geographical area of collection play an important role on its chemical composition. The present study investigated the physicochemical properties, total phenolic content and antioxidant capacity of Spanish thyme honey and chestnut honey, and their mixtures with royal jelly (2% and 10%) and propolis (2% and 10%). The analysis of the physicochemical parameters of both honey samples showed values within the established limits. Propolis showed the highest value of total phenolic content (17.21–266.83 mg GAE/100 g) and antioxidant capacity (DPPH, ORAC and ABTS assays; 0.63–24.10 µg eq. Tx/g, 1.61–40.82 µg eq. Tx/g and 1.89–68.54 µg eq. Tx/g, respectively), and significantly reduced ROS production in human hepatoma cells. In addition, mixtures of honey with 10% of propolis improved the results obtained with natural honey, increasing the value of total phenolic content and antioxidant capacity. A significant positive correlation was observed between total phenolic compounds and antioxidant capacity. Therefore, the antioxidant capacity could be attributed to the phenolic compounds present in the samples, at least partially. In conclusion, our results indicated that thyme and chestnut honey supplemented with propolis can be an excellent natural source of antioxidants and could be incorporated as a potential food ingredient with biological properties of technological interest, added as a preservative. Moreover, these mixtures could be used as natural sweeteners enriched in antioxidants and other bioactive compounds.

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

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

Propolis: An update on its chemistry and pharmacological applications

Propolis, a resinous substance produced by honeybees from various plant sources, has been used for thousands of years in traditional medicine for several purposes all over the world. The precise composition of propolis varies according to plant source, seasons harvesting, geography, type of bee flora, climate changes, and honeybee species at the site of collection. This apiary product has broad clinical applications such as antioxidant, anti-inflammatory, antimicrobial, anticancer, analgesic, antidepressant, and anxiolytic as well asimmunomodulatory effects. It is also well known from traditional uses in treating purulent disorders, improving the wound healing, and alleviating many of the related discomforts. Even if its use was already widespread since ancient times, after the First and Second World War, it has grown even more as well as the studies to identify its chemical and pharmacological features, allowing to discriminate the qualities of propolis in terms of the chemical profile and relative biological activity based on the geographic place of origin. Recently, several in vitro and in vivo studies have been carried out and new insights into the pharmaceutical prospects of this bee product in the management of different disorders, have been highlighted. Specifically, the available literature confirms the efficacy of propolis and its bioactive compounds in the reduction of cancer progression, inhibition of bacterial and viral infections as well as mitigation of parasitic-related symptoms, paving the way to the use of propolis as an alternative approach to improve the human health. However, a more conscious use of propolis in terms of standardized extracts as well as new clinical studies are needed to substantiate these health claims.

Computational Study of Asian Propolis Compounds as Potential Anti-Type 2 Diabetes Mellitus Agents by Using Inverse Virtual Screening with the DIA-DB Web Server, Tanimoto Similarity Analysis, and Molecular Dynamic Simulation

Propolis contains a wide range of pharmacological activities because of their various bioactive compounds. The beneficial effect of propolis is interesting for treating type-2 diabetes mellitus (T2DM) owing to dysregulation of multiple metabolic processes. In this study, 275 of 658 Asian propolis compounds were evaluated as potential anti-T2DM agents using the DIA-DB web server towards 18 known anti-diabetes protein targets. More than 20% of all compounds could bind to more than five diabetes targets with high binding affinity (<−9.0 kcal/mol). Filtering with physicochemical and pharmacokinetic properties, including ADMET parameters, 12 compounds were identified as potential anti-T2DM with favorable ADMET properties. Six of those compounds, (2R)-7,4′-dihydroxy-5-methoxy-8-methylflavone; (RR)-(+)-3′-senecioylkhellactone; 2′,4′,6′-trihydroxy chalcone; alpinetin; pinobanksin-3-O-butyrate; and pinocembrin-5-methyl ether were first reported as anti-T2DM agents. We identified the significant T2DM targets of Asian propolis, namely retinol-binding protein-4 (RBP4) and aldose reductase (AKR1B1) that have important roles in insulin sensitivity and diabetes complication, respectively. Molecular dynamic simulations showed stable interaction of selected propolis compounds in the active site of RBP4 and AKR1B1. These findings suggest that Asian propolis compound may be effective for treatment of T2DM by targeting RBP4 and AKR1B1.

Evaluating the effects of a standardized polyphenol mixture extracted from poplar-type propolis on healthy and diseased human gut microbiota

INTRODUCTION

A large body of evidence suggests that propolis exerts antioxidant, anti-inflammatory, and antimicrobial activities, mostly ascribed to its polyphenol content. Growing evidence suggests that propolis could modulate gut microbiota exerting a positive impact on several pathological conditions. The aim of this study was to determine the in vitro impact of a poplar-type propolis extract with a standardized polyphenol content, on the composition and functionality of gut microbiota obtained from fecal material of five different donors (healthy adults, and healthy, obese, celiac, and food allergic children).

METHODS

The standardized polyphenol mixture was submitted to a simulated in vitro digestion-fermentation process, designed to mimic natural digestion in the human oral, gastric, and intestinal chambers. The antioxidant profile of propolis before and after the digestion-fermentation process was determined. 16 S rRNA amplicon next-generation sequencing (NGS) was used to test the effects on the gut microbiota of propolis extract. The profile of the short-chain fatty acids (SCFA) produced by the microbiota was also investigated through a chromatographic method coupled with UV detection.

RESULTS

In vitro digestion and fermentation induced a decrease in the antioxidant profile of propolis (i.e., decrease of total polyphenol content, antiradical and reducing activities). Propolis fermentation exhibited a modulatory effect on gut microbiota composition and functionality of healthy and diseased subjects increasing the concentration of SCFA.

CONCLUSIONS

Overall, these data suggest that propolis might contribute to gut health and could be a candidate for further studies in view of its use as a prebiotic ingredient.

Evaluation of Total Phenolic and Flavonoid Contents, Antibacterial and Antibiofilm Activities of Hungarian Propolis Ethanolic Extract against Staphylococcus aureus

Propolis is a natural bee product that is widely used in folk medicine. This study aimed to evaluate the antimicrobial and antibiofilm activities of ethanolic extract of propolis (EEP) on methicillin-resistant and sensitive Staphylococcus aureus (MRSA and MSSA). Propolis samples were collected from six regions in Hungary. The minimum inhibitory concentrations (MIC) values and the interaction of EEP-antibiotics were evaluated by the broth microdilution and the chequerboard broth microdilution methods, respectively. The effect of EEP on biofilm formation and eradication was estimated by crystal violet assay. Resazurin/propidium iodide dyes were applied for simultaneous quantification of cellular metabolic activities and dead cells in mature biofilms. The EEP1 sample showed the highest phenolic and flavonoid contents. The EEP1 successfully prevented the growth of planktonic cells of S. aureus (MIC value = 50 µg/mL). Synergistic interactions were shown after the co-exposition to EEP1 and vancomycin at 108 CFU/mL. The EEP1 effectively inhibited the biofilm formation and caused significant degradation of mature biofilms (50-200 µg/mL), as a consequence of the considerable decrement of metabolic activity. The EEP acts effectively as an antimicrobial and antibiofilm agent on S. aureus. Moreover, the simultaneous application of EEP and vancomycin could enhance their effect against MRSA infection.

Polyphenolics profile effects upon the antioxidant and antimicrobial activity of propolis extracts

Propolis, a complex bee product, is a source of numerous bioactive principles, beneficial for human health, therefore it is intensively studied. In the present work, extracts of propolis from Bihor Romanian County were studied to identify the relationship between the polyphenolic derivatives profile and their antioxidant and antimicrobial activity. Extracts were obtained using water and 25%, 50%, and 70% ethanolic solutions (w/w), at 2:1, 4:1, and 6:1 liquid: solid ratios (w/w). 21 polyphenolic derivatives were quantified by UHPLC-MS, proving that the extracts composition strongly depends on the solvent. The sum of quantified polyphenolics extracted varied between 1.5 and 91.2 mg/g propolis. The antioxidant capacity was evaluated using the free radicals 2,2’-azino-bis (3-ethylbenzothiazoline-6 sulfonic acid) diammonium salt (ABTS) and 1-diphenyl-2-picryl-hydrazyl (DPPH) scavenging methods. Antimicrobial efficiency was tested against Gram-positive (B. subtilis), Gram-negative bacteria (E. coli), and fungi (C. albicans) by disc-diffusion method. All extracts, even the aqueous ones, demonstrated antibacterial and antifungal activity. Chemometric methods (partial least squares) and a saturation-type model were used to evaluate the contribution of various bioactive principles in building the antioxidant capacity of extracts. Both experimental and modelling results show that 50% ethanolic extracts provide a rich polyphenolics profile and ensure a good antioxidant capacity.

Chemical and biological characteristics of propolis from Apis mellifera caucasica from the Ardahan and Erzurum provinces of Turkey: a comparative study

The aim of this study was to compare the biological activities of ethanolic propolis extracts of Apis mellifera caucasica obtained from Ardahan and Erzurum provinces of Turkey. Samples were tested for antioxidant, anticytotoxic, anticarcinogenic, antibacterial, and antifungal potentials using different techniques. Propolis samples from the two provinces had different mineral and organic compositions related to their geographical origin. The ferric reducing antioxidant power (FRAP) test showed superiority of Ardahan propolis over the Erzurum. Regardless of origin and the presence of mitomycin C in the culture medium, propolis enhanced human peripheral lymphocyte viability, which depended on the duration and propolis concentration. Antiperoxidative activity on MCF-7 breast cancer cells was concentration-dependent. Erzurum propolis showed the highest anticarcinogenic activity at the concentrations of 62.5 μg/mL and 125 μg/ mL, which dropped at higher concentrations. All propolis samples also showed antibacterial activity against the tested human pathogens similar to ampicillin and penicillin controls, except for Pseudomonas aeruginosa. However, they did not exert any antifungal activity against Candida albicans and Yarrowia lipolytica. In conclusion, propolis samples from both provinces showed promising biological activities, but further research should focus on finding the right concentrations for optimal effect and include the cell necrosis pathway to get a better idea of the anticarcinogenic effects.

Antioxidant Activity in Bee Products: A Review

Bee products have been used since ancient times both for their nutritional value and for a broad spectrum of therapeutic purposes. They are deemed to be a potential source of natural antioxidants that can counteract the effects of oxidative stress underlying the pathogenesis of many diseases. In view of the growing interest in using bioactive substances from natural sources to promote health and reduce the risk of developing certain illnesses, this review aims to update the current state of knowledge on the antioxidant capacity of bee products such as honey, pollen, propolis, beeswax, royal jelly and bee venom, and on the analytical methods used. The complex, variable composition of these products and the multitude of analytical methods used to study their antioxidant activities are responsible for the wide range of results reported by a plethora of available studies. This suggests the need to establish standardized methods to more efficiently evaluate the intrinsic antioxidant characteristics of these products and make the data obtained more comparable.

Potential of Propolis Extract as a Natural Antioxidant and Antimicrobial in Gelatin Films Applied to Rainbow Trout (Oncorhynchus mykiss) Fillets

Usage of edible films and coatings alone or incorporated with natural extracts are a new approach to preservation and packaging of food. In this study, therefore, the microbiological, chemical quality, and sensorial changes of rainbow trout fillets coated with gelatin films supplemented with propolis extract (PE) (2, 8, 16%), as a source of polyphenols, were determined during 15 days of refrigerated storage (4 ± 1 °C). According to peroxide value (PV) and thiobarbituric acid reactive substances (TBARS) assays, lipid oxidation was delayed in the fillets coated with gelatin films incorporated with PE comparing with the control and gelatin-coated (without PE) fillets. The total volatile basic nitrogen (TVB-N) value of rainbow trout fillets showed an increase in all groups at the end of storage, observing the lowest values in the fillets coated with gelatin films prepared with 16% PE. Gelatin films enriched with PE had great inhibitory effects on the microbial growth in rainbow trout fillets. The addition of PE enhanced the effectiveness of gelatin films and delayed the lipid oxidation and sensory and microbial deterioration in trout fillets coated with these films. Thus, PE can be recommended to be used as a natural antioxidant and antimicrobial additive with gelatin films to maintain rainbow trout fillet quality.

Industrial freezing effects on the content and bioaccessibility of spinach (Spinacia oleracea L.) polyphenols

BACKGROUND

Spinach is well recognized as a functional food owing to its diverse nutritional composition, including polyphenols. Freezing is an efficient preservation method that is used to maintain the physical and nutritional characteristics and extend the shelf life of spinach. The aim of this study was to determine the changes in polyphenols in the samples taken from various production steps of the industrial freezing process of spinach, and to evaluate the bioaccessibility of these bioactive compounds for raw material, by-product, and frozen product using the standardized in vitro digestion model simulating the digestion in the mouth, stomach, and intestine.

RESULTS

Ultra-performance liquid chromatography coupled to electrospray ionization tandem mass spectrometry and high-performance liquid chromatography equipped with photodiode array detection analysis of spinach samples led to the identification of eight flavonoids and two phenolic acids. The changes occurring in flavonoids after blanching, chopping, and freezing steps were statistically not significant compared with the raw material (P > 0.05). On the other hand, by-product was found to contain significantly lower amounts of flavonoids (98% in total) and phenolic acids (90% in total) (P < 0.05) compared with the raw material. Furthermore, after in vitro digestion, frozen spinach was found to contain higher amounts of bioaccessible flavonoids (15% in total) and phenolic acids (16% in total) compared with fresh spinach.

CONCLUSION

Overall, the current study highlighted that industrial freezing might be a good strategy to preserve the polyphenol content of fresh spinach as well as to enhance the total amount of bioaccessible polyphenols.

Catechin isolated from cashew nut shell exhibits antibacterial activity against clinical isolates of MRSA through ROS-mediated oxidative stress

Staphylococcus aureus causes severe infections and among all methicillin-resistant S. aureus (MRSA) remains a great challenge in spite of decade research of antibacterial compounds. Even though some synthetic antibiotics have been developed, they are not effective against MRSA, and hence, there is a search for natural, alternative and plant-based antibacterial compound. In this connection, catechin isolated from cashew nut shell was investigated for its antibacterial potential against MRSA. Catechin exhibited zone of inhibition (ZOI) and minimum inhibitory concentration (MIC) in a range of 15.1-19.5 mm and 78.1-156.2 μg/ml, respectively, against ATCC and clinical isolates of MRSA. Among all clinical isolates, clinical isolate-3 exhibited highest sensitivity to catechin. Catechin has arrested the growth of MRSA strains and also caused toxicity by membrane disruption which was illustrated by AO/EB fluorescence staining. Increased nucleic acid leakage (1.58-28.6-fold) and protein leakage (1.40-23.50-fold) was noticed in MRSA due to catechin treatment when compared to methicillin. Bacteria treated with catechin at its MIC showed 1.52-, 1.87- and 1.74-fold increase of ROS production in methicillin susceptible S. aureus (MSSA), MRSA and clinical isolate-3 strains, respectively, as compared to control. Superoxide dismutase (5.31-9.63 U/mg protein) and catalase (1573-3930 U/mg protein) were significantly decreased as compared to control in catechin-treated S. aureus. Thus, catechin exhibited antibacterial activity through oxidative stress by increased production of ROS and decreased antioxidant enzymes. Altogether results suggest that catechin is a promising lead compound with antibacterial potential against MRSA. KEY POINTS: • Catechin was isolated and identified as active compound in cashew nut shell. • Catechin exhibited antimicrobial activity against clinical isolates of MRSA. • Bacterial cell wall damage was caused by catechin in MRSA strains. • Catechin increased the oxidative stress in MRSA by intracellular ROS production.

Bioresource Utilization of Djulis (Chenopodium formosanum) Biomass as Natural Antioxidants

Djulis (Chenopodium formosanum) is a yearly, fast-growing, under-utilized pseudo-cereal with a high proportion of biomass content. We used the hulls, which are usually removed from djulis as crop residue, to evaluate the free-radical scavenging and antioxidant capacity of djulis. We studied the antioxidant capacity of ethanol- and water-extracted hulls and roots by using various in vitro methods. Ascorbic acid was the reference sample. The extract samples were used at 200, 400, 600, 800, and 1000 µg/mL. Total sugar content, total phenolic content, and total flavonoid content were assessed. Antioxidant activity was assessed by using the Trolox equivalent antioxidant capacity, ferric reducing antioxidant power, cupric ion reducing antioxidant capacity, 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity, and N, N-dimethyl-ρ-phenylenediamine. Ethanol- and water-extracted red djulis hulls showed high amounts of total sugar, total phenolic content, total flavonoid content, and antioxidant capacity. Moreover, ethanol- and water-extracted red djulis roots showed moderate antioxidant capacity. However, ethanol- and water-extracted yellow djulis hulls showed limited antioxidant activities. Utilization of the biomass of djulis hulls and roots as natural antioxidant resources may be environmentally friendly and foreseeable.

Influence of ultrasonic amplitude, temperature, time and solvent concentration on bioactive compounds extraction from propolis

An ultrasound assisted method was investigated to extract bioactive compounds from propolis. This method was based on a simple ultrasound treatment using ethanol as an extraction medium to facilitate the disruption of the propolis cells. Four different variables were chosen for determining the influence on the extraction efficiency: ultrasonic amplitude, ethanol concentration, temperature and time; the variables were selected by Box-Behnken design experiments. These parameters were optimised in order to obtain the highest yield, and the results exhibited the optimum conditions for achieving the goal as 100% amplitude of ultrasonic treatment, 70% solvent concentration, 58 °C and 30 min. The extraction yield under modified optimum extraction conditions was, as follows: 459.92 mg GAE/g of TPC, 220.62 mg QE/g of TFC and 1.95% of balsam content. The results showed that the ultrasound assisted extraction was suitable for bioactive compounds extraction from propolis. The most abundant phenolic compound was kaempferol (228.8 mg/g propolis) followed by myricetin (115.5 mg/g propolis), luteolin (27.2 mg/g propolis) and quercetin (25.2 mg/g propolis).

Are Supplements Safe? Effects of Gallic and Ferulic Acids on In Vitro Cell Models

Polyphenols display health-promoting properties linked to their biological activities. They are initially absorbed in the small intestine, then they are largely metabolized in the colon, whereupon they are able to exert systemic effects. The health-promoting properties of polyphenols have led to the development of food supplements, which are also largely consumed by healthy people, even if data on their safety are still yet lacking. In the present paper, the content of gallic acid and ferulic acid was analyzed in two supplements, and shown to be higher than the relative contents found in fruit and flour. To evaluate the effects of these phenolic compounds on epithelial intestinal tissue, gallic and ferulic acids were added to a new in vitro model of the intestinal wall at different concentrations. The effects on viability, proliferation and migration of these compounds were respectively tested on three different cell lines (Caco2, L929 and U937), as well as on a tridimensional intestinal model, composed of a mucosal layer and a submucosa with fibroblasts and monocytes. Results indicated that gallic and ferulic acids can exert toxic effects on in vitro cell models at high concentrations, suggesting that an excessive and uncontrolled consumption of polyphenols may induce negative effects on the intestinal wall.

Novel Siwa propolis and colistin-integrated chitosan nanoparticles: elaboration; in vitro and in vivo appraisal

Aim: The present study aimed to formulate novel cremophore-decorated chitosan nanoparticles of colistin, integrated with Siwa propolis extract, to solve bacterial resistance to colistin. Materials & methods: The novel nanoformula was prepared using an incorporation method. Physicochemical assessment and in vivo studies of the selected nanoformulations were performed. Results: The nanoformulation exhibited a nanosize of 48.3 nm, high ζ potential (43.6 mV), high entrapment efficiency (75%) and complete bacterial growth eradication within 2 h (minimum inhibitory concentration = 6.25 μg/ml). Histological examination showed that incorporation of colistin into the nanoformulation could successfully prevent its nephrotoxicity. Conclusion: Tailoring of proper nanocarrier could successfully revert bacteria from being colistin-resistant to colistin-sensitive. The developed nanoformulation can be considered as a potential antibacterial agent in pneumonia treatment.

Chemical Composition and Antioxidant Activity of Essential Oil of Chinese Propolis

The chemical composition and in vitro antioxidant activity of the essential oil of propolis (EOP) collected from 25 locations in China was investigated. Steam-distillation extraction was used to extract the EOP, and chemical composition was identified by GC/MS. The antioxidant activities of EOP were also measured. The result showed that a total of 406 compounds were detected in EOP. The major compounds of Chinese EOP were cedrol, γ-eudesmol, benzyl alcohol, phenethyl alcohol, 2-methoxy-4-vinylphenol, 3,4-dimethoxystyrene and guaiol. Principal component analysis revealed the significant correlation between EOP compositions and their origins, and certain correlation was detected between EOP and their color. Linear discriminant analysis showed that 88 % and 84 % of the propolis samples were predicted correctly as the groupings identified by climatic zone and the color, respectively. Furthermore, the differences of antioxidant activities of EOP were significant. EOP of Shandong had the strongest antioxidant activities, whereas EOP of Guangdong, Yunnan and Hunan showed the poorest.

Chitosan coatings incorporated with propolis extract and Zataria multiflora Boiss oil for active packaging of chicken breast meat

The impact of dipping in combination of propolis extract (PE) and chitosan (CH) coating enriched with Zataria multiflora essential oil (ZEO) on chemical, microbial and organoleptic properties of poultry meat was determined at 4 °C. GC-MS analysis showed that the most components of PE were Dihydrochrysin (9.69%) and b- Pinostrobin (7.41%). The results of mesophilic total viable plate counts (TVC), lactic acid bacteria (LAB), Psychotropic bacteria and Pseudomonas spp. showed detectably lower (p < 0.05) microbial count in CH-PE 1%-Z 0.5% and CH-PE 1%-Z 1% samples at the last day of storage. The results of chemical characteristics (pH, total volatile base nitrogen (TVB-N), 2-thiobarbituric acid reactive substances (TBARS)) in all treated samples compared with the control, revealed that there is a synergistic effect between CH, PE and ZEO. In the sensorial assessment, treatments containing 1% PE- 0.5% ZEO and 1% PE- 1% ZEO were mostly acceptable by the sensory analyst. These results offer a successful approach that chitosan coating enriched with combination of ZEO and PE can be an improving method to reducing deterioration of fresh packed chicken meat.