The effect of propolis extract on milk production and composition, serum biochemistry, and physiological parameters of heat-stressed dairy cows.

The aim of this study was to evaluate whether feeding propolis extract (PE) influences nutrient intake, milk production and composition, serum biochemistry, and physiological parameters of heat-stressed dairy cows. For this purpose, we used three primiparous Holstein cows with a lactation period of 94 ± 4 days and with 485 ± 13 kg body weight. The treatments were 0 mL/day, 32 mL/day, and 64 mL/day of PE randomly assigned in a 3x3 Latin square design, repeated over time. The experiment lasted a total of 102 days; each Latin square lasted 51 days divided into three 17-day periods (12 days for adaptation and five days for data collection). The PE supply did not influence (P > 0.05) the cows' intake of dry matter (18.96 kg/d), crude protein (2.83 kg/d), and neutral detergent-insoluble fiber (7.36 kg/d), but there was an increase in feeding time with the 64 ml/day PE supply (P < 0.05). Providing 64 ml/day of PE tended (P = 0.06) to increase milk production by 11.64% and improve gross feed efficiency of cows by 12.04%. The PE supply did not influence milk composition and blood parameters of cows (P > 0.05). Offering 32 mL/day of PE decreased (P < 0.05) the rectal temperature and respiratory rate of cows. We recommend a supply of 64 mL/day of PE for heat-stressed dairy cows.

Lipidomic analysis of geopropolis of Brazilian stingless bees by LC-HRMS.

Stingless bees (Meliponini) represent over than 500 species, found in tropical and sub-tropical regions of the world. They produce geopropolis, a resinous natural product containing bioactive compounds, which is commonly used in folk medicine. In the current study, LC-HRMS and bioinformatic tools were used to carry out for the first time the lipidomic analysis of geopropolis from indigenous Brazilian stingless bees. As a result, 61 compounds of several lipid classes were identified with elevated degree of confidence. Then, we demonstrated that lipids in geopropolis are not restricted to waxes and fatty acids; but fatty amides and amines, phenolic lipids, resorcinols, retinoids, abietanoids, diterpenoids, pentacyclic triterpenoids, prostaglandins, retinoids, and steroids were found. In addition, multivariate analysis, based on the lipidomic profile of extracts, reinforces the assumption that the species of stingless bees, as well as the geographical origin are relevant factors to affect geopropolis composition once that the lipidic profile allowed the discrimination of geopropolis in groups related to the geographical origin, bee specie or bee genus. The lipidic profile also suggest a selective forage habits of T. angustula, which seems to collect resins from more specific vegetal sources regardless geographic origin, while other stingless bees, such as M. marginata and M. quadrifasciata, are less selective and may adapt to collect resins from a wider variety of plants.

Bee pollen and bee bread nutritional potential: Chemical composition and macronutrient digestibility under in vitro gastrointestinal system.

Bee pollen (BP) and bee bread (BB) have been often investigated as potential functional foods. Both bee products are generally characterized by their high nutritional content, with BB being referred as more digestible than BP, however, there is a lack of scientific studies proving this claim. Here, we present a comparative evaluation of the macronutrient digestibility of BP and BB after applying a simulated in vitro gastrointestinal digestive system, together with the evaluation of its nutritional value and chemical composition. The digestibility scores for protein content were calculated on average as 69% and 76% for BP and BB, respectively, whereas digestibility scores for soluble sugars varied depending on bee product and sugar type. The results demonstrated that the nutritional values of both bee products changed depending on their botanical origin but BB is more accessible in the intestinal lumen, especially regarding protein.

Ultra-high-performance liquid chromatography using a fused-core particle column for fast analysis of propolis phenolic compounds.

Propolis is a bee product with a complex chemical composition formed by several species from different geographical origins. The complex propolis composition requires an accurate and reproducible characterization of samples to standardize the quality of the material sold to consumers. This work developed an ultra-high-performance liquid chromatography with a photodiode array detector method to analyze propolis phenolic compounds based on the two key propolis biomarkers, Artepillin C and p-Coumaric acid. This choice was made due to the complexity of the sample with the presence of several compounds. The optimized method was hyphenated with mass spectrometry detection allowing the detection of 23 different compounds. A step-by-step strategy was used to optimize temperature, flow rate, mobile phase composition, and re-equilibration time. Reverse-phase separation was achieved with a C18 fused-core column packed with the commercially available smallest particles (1.3 nm). Using a fused-core column with ultra-high-performance liquid chromatography allows highly efficient, sensitive, accurate, and reproducible determination of compounds extracted from propolis with an outstanding sample throughput and resolution. Optimized conditions permitted the separation of the compounds in 5.50 min with a total analysis time (sample-to-sample) of 6.50 min.

Applicability of an HPLC method for analysis of alcoholic and glycolic Brazilian green-propolis extracts

Abstract Brazilian green propolis has been widely used in food and pharmaceutical products due to its valuable source of phenolic compounds and versatile biological activities. The development and validation of analytical methods are extremely useful for the characterization and quality control of products containing propolis. Therefore, the aim of this study was to optimize, validate and investigate the applicability of a reversed-phase HPLC method for analysis of different types of Brazilian green propolis extracts (glycolic and ethanolic). The method showed to be selective for the propolis phenolic markers. The analysis of variance and residues demonstrated that the method had significant linear regression, without lack of fit. It was also a precise, accurate and robust method, which was of utmost importance to analyze both glycolic and ethanolic extracts and at different concentrations. Moreover, as these products can display most complex matrices to analyze, a valid HPLC method can also prove to be specific and versatile.

Down-regulation of complement genes in lipopolysaccharidechallenged zebrafish (Danio rerio) larvae exposed to Indonesian propolis / Regulação negativa dos genes do complemento em larvas de peixe-zebra (Danio rerio) desafiadas com lipopolissacarídeo expostas à própolis indonésia

Although propolis has been reported for having anti-inflammatory activities, its effects on complement system has not been much studied. This research was conducted to find out the effects of Indonesian propolis on the expression levels of C3, C1r/s, Bf, MBL, and C6 in zebrafish larvae which were induced by lipopolysaccharide (LPS). Counting of macrophages migrating to yolk sac and liver histology were carried out. Larvae were divided into four groups: CON (cultured in E3 medium only), LPS (cultured in a medium containing 0.5 μg/L LPS), LPSIBU (cultured in a medium containing LPS, and then treated with 100 μg/L ibuprofen for 24 hours), and LPSPRO (cultured in a medium containing LPS, and then immersed in 14,000 μg/L propolis for 24 hours) groups. The results showed that complement gene expression in larvae from the LPSIBU and LPSPRO groups were generally lower than in larvae from the LPS group. The number of macrophage migrations to the yolk in the LPSPRO group was also lower than in the LPS group. Histological structure of liver in all groups were considered normal. This study shows that Indonesian propolis has the potential to be used as an alternative to the substitution of NSAIDs.

Embora a própolis tenha sido relatada por ter atividade anti-inflamatória, seus efeitos no sistema complemento, uma parte do sistema imunológico inato, não foram muito estudados. Esta pesquisa foi conduzida para descobrir os efeitos da própolis da Indonésia nos níveis de expressão de C3, C1r/s, Bf, MBL e C6 em larvas de peixe-zebra induzidas por lipopolissacarídeo (LPS). Foram realizadas contagens de macrófagos que migram para o saco vitelino e histologia do fígado. As larvas foram divididas em quatro grupos: CON (cultivadas apenas em meio E3), LPS (cultivadas em meio contendo 0,5 μg/L de LPS), LPSIBU (cultivadas em meio contendo LPS e, em seguida, tratadas com 100 μg/L de ibuprofeno por 24 horas) e LPSPRO (cultivado em meio contendo LPS, e então imerso em própolis 14,000 μg/L por 24 horas). Os resultados mostraram que a expressão do gene do complemento em larvas dos grupos LPSIBU e LPSPRO foi geralmente menor que em larvas do grupo LPS. O número de migrações de macrófagos para a gema no grupo LPSPRO também foi menor que no grupo LPS. A estrutura histológica do fígado em todos os grupos foi considerada normal. Este estudo mostra que a própolis indonésia tem potencial para ser utilizada como alternativa na substituição dos AINEs (anti-inflamatórios não esteroides).

Short- and medium-chain chlorinated paraffins in honey from China: Distribution, source analysis, and risk assessment.

Chlorinated paraffins (CPs) are industrial chemicals produced in large quantities. Short-chain CPs (SCCPs) were classified as persistent organic pollutants under the Stockholm Convention in 2017. Medium-chain CPs (MCCPs) became candidate persistent organic pollutants in 2021. CPs are now ubiquitously found in the environment. Honey bees can be exposed to CPs during foraging, and this exposure subsequently results in the contamination of honey and other bee products along with colony food production and storage. Here, SCCP and MCCP concentrations in honey collected from Chinese apiaries in 2015 and 2021 were determined. Total CP concentrations in honey from 2021 to 2015 were comparable, but the ratio of MCCPs/SCCPs was higher in 2021 than in 2015. SCCP and MCCP congener group profiles in all honey samples were similar and dominated by C10-11Cl6-7 and C14Cl6-7, respectively. MCCP concentrations were also higher than SCCP concentrations in bees, pollen, and wax but not in bee bread, which were all collected in 2021. The order of average CP concentrations was determined as wax > bee > pollen > bee bread > honey. Poor relationships were found between SCCP concentrations in honey and other samples, but a relationship between MCCP concentrations in honey and other samples was observed. Migration tests of CPs in plastic bottles showed essentially no migration into honey during storage. The risks to humans from CPs in honey are low.

Thin-layer chromatography in the authenticity testing of bee-products.

Quality control, nutritional value and the monitoring of hazardous residues in honey bee- products have become major topics for both producers and consumers. Due to its potential role in human health, bee-products rich in bioactive compounds are becoming increasingly popular. This review aims to provide an overview of thin-layer chromatography methods used in quality control,authenticity testing and chemical profiling of bee-products in order to help scientists engaged in the field of bee-products chemistry to utilize the advantages of this technique in the detection and elimination of fraudulent practices in bee-product manufacturing. Recently, hyphenation of thin-layer chromatography, image analysis and chemometrics support bee-products analysisbysimultaneousdeterminationofanalytes with different detection principles, identification of individual bioactive compounds as well as structure elucidation of compounds. Highlighted opportunities of thin-layer chromatography could encourage further investigations that would lead to improvements in the detection and elimination of marketing fraudulent practices.

Chemical profiling, HPLC characterization and in-vitro antioxidant potential of Pakistani propolis collected from peripheral region of Faisalabad.

Propolis is a highly adhesive and resinous product of honey bee (Apis mellifera L.) which is produced from the exudations of plants. Bee propolis being a source of bioactive compounds like polyphenols and flavonoids imparts numerous biological properties including, antioxidant, anti-inflammatory, antimicrobial and anticancer activities. Present study was designed to elucidate the composition and antioxidant status of locally available propolis using in-vitro conditions. Propolis collected from locally found apiaries and its hydroalcoholic extract of propolis was prepared using different concentrations of ethanol and methanol. The results regarding proximate composition of propolis showed a higher proportion of ether extract (85.59±0.87%) and lowest contents of crude fiber (0.31±0.08%). Among the mineral's sodium, potassium and calcium was found in a concentration of 11.33±0.91, 52.10±2.9 and 10.53±0.83.59±0.23mg/Kg respectively whilst zinc was noticed as 3.59±0.23mg/Kg. HPLC characterization indicates a highest concentration of Chlorogenic acid 31.80±2.56mg/Kg whereas gallic acid (0.21±0.01mg/Kg) was found in lowest concentration among the polyphenols. Ethanol extract represents more phenolic contents, DPPH activity and antioxidant status as 327.30±14.89mg/gGAE, 73.18±4.43% and 60.59±4.38% accordingly in comparison to methanol and water extract. Bee propolis found an effective source of natural antioxidants which retards the production of free radicals and reactive oxygen species thus help to cope oxidative stress.

Synthesis, antitumor activity and in silico analyses of amino acid derivatives of artepillin C, drupanin and baccharin from green propolis.

Breast cancer has the highest incidence and mortality in females, while prostate cancer has the second-highest incidence in males. Studies have shown that compounds from Brazilian green propolis have antitumor activities and can selectively inhibit the AKR1C3 enzyme, overexpressed in hormone-dependent prostate and breast tumors. Thus, in an attempt to develop new cytotoxic inhibitors against these cancers, three prenylated compounds, artepillin C, drupanin and baccharin, were isolated from green propolis to synthesize new derivatives via coupling reactions with different amino acids. All obtained derivatives were submitted to antiproliferative assays against four cancer cells (MCF-7, MDA MB-231, PC-3, and DU145) and two normal cell lines (MCF-10A and PNT-2) to evaluate their cytotoxicity. In general, the best activity was observed for compound6e, derived from drupanin, which exhibited half-maximal inhibitory concentration (IC50) of 9.6 ± 3 µM and selectivity index (SI) of 5.5 against MCF-7 cells.In silicostudies demonstrated that these derivatives present coherent docking interactions and binding modes against AKR1C3, which might represent a possible mechanism of inhibition in MCF-7 cells.

An Analytical Method for the Biomonitoring of Mercury in Bees and Beehive Products by Cold Vapor Atomic Fluorescence Spectrometry.

Bees and their products are useful bioindicators of anthropogenic activities and could overcome the deficiencies of air quality networks. Among the environmental contaminants, mercury (Hg) is a toxic metal that can accumulate in living organisms. The first aim of this study was to develop a simple analytical method to determine Hg in small mass samples of bees and beehive products by cold vapor atomic fluorescence spectrometry. The proposed method was optimized for about 0.02 g bee, pollen, propolis, and royal jelly, 0.05 g beeswax and honey, or 0.1 g honeydew with 0.5 mL HCl, 0.2 mL HNO3, and 0.1 mL H2O2 in a water bath (95 °C, 30 min); samples were made up to a final volume of 5 mL deionized water. The method limits sample manipulation and the reagent mixture volume used. Detection limits were lower than 3 µg kg-1 for a sample mass of 0.02 g, and recoveries and precision were within 20% of the expected value and less than 10%, respectively, for many matrices. The second aim of the present study was to evaluate the proposed method's performances on real samples collected in six areas of the Lazio region in Italy.

Activity of Compounds from Temperate Propolis against Trypanosoma brucei and Leishmania mexicana.

Ethanolic extracts of samples of temperate zone propolis, four from the UK and one from Poland, were tested against three Trypanosoma brucei strains and displayed EC50 values < 20 µg/mL. The extracts were fractionated, from which 12 compounds and one two-component mixture were isolated, and characterized by NMR and high-resolution mass spectrometry, as 3-acetoxypinobanksin, tectochrysin, kaempferol, pinocembrin, 4'-methoxykaempferol, galangin, chrysin, apigenin, pinostrobin, cinnamic acid, coumaric acid, cinnamyl ester/coumaric acid benzyl ester (mixture), 4',7-dimethoxykaempferol, and naringenin 4',7-dimethyl ether. The isolated compounds were tested against drug-sensitive and drug-resistant strains of T. brucei and Leishmania mexicana, with the highest activities ≤ 15 µM. The most active compounds against T. brucei were naringenin 4',7 dimethyl ether and 4'methoxy kaempferol with activity of 15-20 µM against the three T. brucei strains. The most active compounds against L. mexicana were 4',7-dimethoxykaempferol and the coumaric acid ester mixture, with EC50 values of 12.9 ± 3.7 µM and 13.1 ± 1.0 µM. No loss of activity was found with the diamidine- and arsenical-resistant or phenanthridine-resistant T. brucei strains, or the miltefosine-resistant L. mexicana strain; no clear structure activity relationship was observed for the isolated compounds. Temperate propolis yields multiple compounds with anti-kinetoplastid activity.

Characterizing the Volatile and Sensory Profiles, and Sugar Content of Beeswax, Beebread, Bee Pollen, and Honey.

Bee products are a well-known remedy against numerous diseases. However, from the consumers' perspective, it is essential to define factors that can affect their sensory acceptance. This investigation aimed to evaluate the volatile and sensory profiles, and sugar composition of beeswax, beebread, pollen, and honey. According to the HS-SPME/GC-MS results, 20 volatiles were identified in beeswax and honey, then 32 in beebread, and 33 in pollen. Alkanes were found to dominate in beeswax, beebread, and pollen, while aldehydes and monoterpenes in honey. In the case of sugars, a higher content of fructose was determined in beebread, bee pollen, and honey, whereas the highest content of glucose was assayed in beeswax. In the QDA, the highest aroma intensity characterized as honey-like and sweet was found in honey, while the acid aroma was typical of beebread. Other odor descriptors, including waxy, pungent, and plant-based aromas were noted only in beeswax, honey, and pollen, respectively.

Isolation of diterpenes from Araucaria sp Brazilian brown propolis and development of a validated high-performance liquid chromatography method for its analysis.

Propolis comprises a complex resinous product composed of plant's parts or exudates, pollen, bee wax, and enzymes. Brazilian brown propolis from Araucaria sp displays several biological activities. Considering the lack of validated analytical methods for its analysis, we are reporting the development of a validated high-performance liquid chromatography with photodiode array detector method to analyze Araucaria brown propolis. The crude propolis were extracted and chromatographed, furnishing six main diterpenes. The isolated standards were used to draw the analytical curves, allowing the studies of selectivity, precision, accuracy, recovery, robustness, the determination of limits of detection and limits of quantification. The mobile phase consisted of 0.1% acetic acid in water and acetonitrile, using an octadecylsilane column, 1 mL/min flow rate and detection at 200 or 241 nm. Relative standard deviation values obtained for intra-day and inter-day precision were lower than 4% for all diterpenes. From the five parameters for robustness, wavelength detection and flow rate were the critical ones. Limits of detection and quantification ranged from 0.808 to 10.359 µg/mL and from 2.448 to 31.392 µg/mL, respectively. The recoveries were between 105.03 and 108.13%, with relative standard deviation values around 5.0%. The developed method is precise, sensitive, and reliable for analyzing Araucaria brown propolis.

Promotion effect of the propolis from Jeju Island, Korea, on NGF secretion in human glioblastoma cells.

Propolis is a resinous mixture of substances collected and processed from various botanical sources by honeybees (Apis mellifera). We previously found that propolis collected on Jeju Island, located off the southern coast of Korea, originates from a single plant, Angelica keiskei KOIDZUMI (Ashitaba). A. keiskei has been well-studied as a health food and has been reported to promote nerve growth factor (NGF) production. Propolis formed from the resin of A. keiskei is expected to have a similar promotional effect on NGF production. NGF is a potential pharmacological agent for Alzheimer's disease. In this study, the effects of an ethanolic extract of propolis from Jeju Island (EEPJ) on NGF secretion and cell viability in T98G human glioblastoma cells were evaluated. Ethanolic extracts of propolis from Brazil (Baccharis type) and from Uruguay (Populus type) were also studied for comparison. We found that EEPJ significantly increased NGF secretion in the cells in a concentration-dependent manner. Furthermore, the effects of 27 compounds previously isolated from EEPJ were also evaluated. Several compounds were found to have a promotion effect on NGF secretion, and the structure-activity relationships of the compounds were considered relative to their promotional effect on NGF biosynthesis. The promotional effect of EEPJ is a characteristic biological activity that is not present with other propolis types, so the propolis from Jeju Island may have potential applications as a therapeutic candidate for Alzheimer's disease.

Multielemental Analysis of Bee Pollen, Propolis, and Royal Jelly Collected in West-Central Poland.

Beehive products possess nutritional value and health-promoting properties and are recommended as so-called "superfoods". However, because of their natural origin, they may contain relevant elemental contaminants. Therefore, to assess the quality of bee products, we examined concentrations of a broad range of 24 selected elements in propolis, bee pollen, and royal jelly. The quantitative analyses were performed with inductively coupled plasma-mass spectrometry (ICP-MS) and inductively coupled plasma optical emission spectrometry (ICP-OES) techniques. The results of our research indicate that bee products contain essential macronutrients (i.e., K, P, and S) and micronutrients (i.e., Zn and Fe) in concentrations depending on the products' type. However, the presence of toxic heavy metals makes it necessary to test the quality of bee products before using them as dietary supplements. Bearing in mind that bee products are highly heterogenous and, depending on the environmental factors, differ in their elemental content, it is necessary to develop standards regulating the acceptable levels of inorganic pollutants. Furthermore, since bees and their products are considered to be an effective biomonitoring tool, our results may reflect the environment's condition in west-central Poland, affecting the health and well-being of both humans and bees.

Daily Brazilian green propolis intake elevates blood artepillin C levels in humans.

BACKGROUND: Propolis is a natural product collected by worker bees from a variety of plant species. As a type of propolis, Brazilian green propolis contains a large amount of artepillin C. Artepillin C is a cinnamic acid derivative and has been shown to have a wide variety of biological functions, including anti-inflammatory, antiviral and antitumor activities, in both cell culture and animal models. However, how propolis is digested and absorbed remains to be elucidated. Moreover, blood artepillin C levels after propolis intake have not been shown in human studies. RESULTS: A randomized, single-blind placebo-controlled study on the effect of Brazilian green propolis on serum artepillin C levels was conducted with healthy volunteers. The participants (n = 133) were randomly allocated in an approximately 2:1 ratio to two groups: propolis (n = 91) and placebo (n = 42). The participants took daily propolis or placebo, and blood tests were performed on day 0 (before propolis intake) and days 1, 3 and 7. Artepillin C was detected in serum in almost all individuals in the propolis groups. No serum artepillin C was detected in the placebo group. Serum artepillin C levels in the female group tended to be higher than those in the male group. In the female group, menstrual status was unrelated to serum artepillin C levels. CONCLUSION: These results suggested that propolis intake might be more effective for females than for males. © 2021 Society of Chemical Industry.

Untargeted Ultrahigh-Performance Liquid Chromatography-Hybrid Quadrupole-Orbitrap Mass Spectrometry (UHPLC-HRMS) Metabolomics Reveals Propolis Markers of Greek and Chinese Origin.

Chemical composition of propolis depends on the plant source and thus on the geographic and climatic characteristics of the site of collection. The aim of this study was to investigate the chemical profile of Greek and Chinese propolis extracts from different regions and suggest similarities and differences between them. Untargeted ultrahigh-performance liquid chromatography coupled to hybrid quadrupole-Orbitrap mass spectrometry (UHPLC-HRMS) method was developed and 22 and 23 propolis samples from Greece and China, respectively, were analyzed. The experimental data led to the observation that there is considerable variability in terms of quality of the distinctive propolis samples. Partial least squares - discriminant analysis (PLS-DA) and orthogonal partial least squares-discriminant analysis (OPLS-DA) models were constructed and allowed the identification of significant features for sample discrimination, adding relevant information for the identification of class-determining metabolites. Chinese samples overexpressed compounds that are characteristic of the poplar type propolis, whereas Greek samples overexpress the latter and the diterpenes characteristic of the Mediterranean propolis type.

A three-year large scale study on the risk of honey bee colony exposure to blooming sunflowers grown from seeds treated with thiamethoxam and clothianidin neonicotinoids.

Despite the restriction of the use of neonicotinoids in the EU, including thiamethoxam and clothianidin, the debate over their risk on honey bees has not been fully settled. This study presents results of a three-year study working with 180 honey bee colonies in ten replicates. Colonies were sorted into three treatments (60 colonies per treatment) exposed to sunflower blooms grown from seeds treated with thiamethoxam, clothianidin and a non-treated control. Each colony was assessed at six moments: one before to exposition to sunflower, two during the exposition (short-time risk), two after exposition (medium-time risk) and one after wintering (long-time risk). The health and development of the colonies were assessed by monitoring adult bee population, brood development, status of the queen, food reserves and survival. No significant difference among treatments when raw data was considered. However, when evolution from initial status of the colony was evaluated, a significant difference was observed from the first week of exposure to sunflower blooms. In this period, the number of adult bees and the amount of brood were slightly lower in the bee hives exposed to neonicotinoids, although such differences disappeared in subsequent evaluations. The concentration of residues in samples of beebread and adult bees was at the level of ng·g-1. Magnitude of the effect of the treatment factor on the variability of colony health and development related parameters was low. The most important factor was the hive, followed by the replicate and year, and to a lesser extent the initial strength of the colonies.

Antioxidative Propolis From Stingless Bees (Heterotrigona Itama) Preserves Endothelium-Dependent Aortic Relaxation of Diabetic Rats: The Role of Nitric Oxide and Cyclic Guanosine Monophosphate

Propolis from stingless bees (Heterotrigona itama) is a resinous compound that exhibits antihyperglycaemia, free radical scavenging, and cardioprotective properties. The effect of propolis on diabetic vessels has not been investigated. Thus, this research aimed to determine the effect of propolis supplementation on the level of antioxidants and its mechanism of action in the aorta of diabetic rats. Male Sprague-Dawley rats were divided into five groups (n=8/group): healthy (control), untreated diabetes (DM), metformin-treated diabetes (DM+M, 300 mg/kg/day metformin), propolis-treated diabetes (DM+P, 300 mg/kg/day propolis extract) and diabetes with combined treatment (DM+M+P, dosage as former). Oral supplementation was conducted for four weeks immediately upon successful induction of diabetes by streptozotocin (60 mg/kg, intraperitoneal injection). At the end of the study, the rats were euthanised, and thoracic aorta was processed into tissue homogenates to determine the levels of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase-1 (GPx-1) and soluble receptor for advanced glycation end-products (sRAGE). Aorta segments were harvested to examine their relaxation response towards graded concentration of acetylcholine (Ach; 10-8-10-4) M following precontraction with phenylephrine (PE; 10-6 M). Vasorelaxation towards a cumulative dose of propolis (0.01-1.00%) using PE-precontracted healthy aorta (n=6/experiments) was investigated under various simulated conditions: physiological buffer, L-NAME (10-4 M), methylene blue (10-5 M), indomethacin (10-5 M) and elevated glucose (25 mM). Propolis maintained antioxidative enzymes and sRAGE decoy molecules in the aortic tissue of the diabetic rats. The amelioration of diabetes-induced impairment of endothelium-dependent relaxation by propolis was mediated through the nitric oxide(NO)-cyclic guanosine monophosphate (cGMP) pathway. This non-clinical study reports vasoprotective property of propolis in diabetes mellitus.