Recent advances in the chemical composition of propolis

Brazilian Green Propolis Improves Antioxidant Function in Patients with Type 2 Diabetes Mellitus

Propolis contains a variety of bioactive components and possesses many biological properties. This study was designed to evaluate potential effects of Brazilian green propolis on glucose metabolism and antioxidant function in patients with type 2 diabetes mellitus (T2DM). In the 18-week randomized controlled study, enrolled patients with T2DM were randomly assigned to Brazilian green propolis group (900 mg/day) (n = 32) and control group (n = 33). At the end of the study, no significant difference was found in serum glucose, glycosylated hemoglobin, insulin, aldose reductase or adiponectin between the two groups. However, serum GSH and total polyphenols were significantly increased, and serum carbonyls and lactate dehydrogenase activity were significantly reduced in the Brazilian green propolis group. Serum TNF-α was significantly decreased, whereas serum IL-1β and IL-6 were significantly increased in the Brazilian green propolis group. It is concluded that Brazilian green propolis is effective in improving antioxidant function in T2DM patients.

Polyphenol-Rich Propolis Extracts Strengthen Intestinal Barrier Function by Activating AMPK and ERK Signaling

Propolis has abundant polyphenolic constituents and is used widely as a health/functional food. Here, we investigated the effects of polyphenol-rich propolis extracts (PPE) on intestinal barrier function in human intestinal epithelial Caco-2 cells, as well as in rats. In Caco-2 cells, PPE increased transepithelial electrical resistance and decreased lucifer yellow flux. PPE-treated cells showed increased expression of the tight junction (TJ) loci occludin and zona occludens (ZO)-1. Confocal microscopy showed organized expressions in proteins related to TJ assembly, i.e., occludin and ZO-1, in response to PPE. Furthermore, PPE led to the activation of AMPK, ERK1/2, p38, and Akt. Using selective inhibitors, we found that the positive effects of PPE on barrier function were abolished in cells in which AMPK and ERK1/2 signaling were inhibited. Moreover, rats fed a diet supplemented with PPE (0.3% in the diet) exhibited increased colonic epithelium ZO-1 expression. Overall, these data suggest that PPE strengthens intestinal barrier function by activating AMPK and ERK signaling and provide novel insights into the potential application of propolis for human gut health.

Nigerian propolis improves blood glucose, glycated hemoglobin A1c, very low-density lipoprotein, and high-density lipoprotein levels in rat models of diabetes

Objective:

According to our previous studies, propolis of Nigerian origin showed some evidence of hypoglycemic and hypolipidemic activities in addition to its ability to ameliorate oxidative-stress-induced organ dysfunction. This study was carried out to determine whether an ethanolic extract of Nigerian propolis (EENP) improves glycated hemoglobin A1c (HbA1c), fasting plasma glucose, very low-density lipoprotein (VLDL), and high-density lipoprotein (HDL) concentrations in rats that have alloxan diabetes.

Materials and Methods:

Diabetes was induced with alloxan (110 mg/kg). Animals were divided into 5 groups (n = 5); Group 1 was non-diabetic receiving normal saline and Group 2 was diabetic but also received only normal saline. Groups 3, 4, and 5 were diabetic receiving 200 mg/kg propolis, 300 mg/kg propolis, and 150 mg/kg metformin, respectively, for 42 days.

Results:

Hyperglycemia, elevated serum level of VLDL, elevated plasma level of HbA1c, and decreased levels of HDL were observed in the diabetic untreated animals. Nigerian propolis decreased blood glucose level and serum level of VLDL but elevated HDL level. These changes were significant (P < 0.05). The levels of plasma HbA1c were also reduced in the propolis-treated groups, and the reduction was significant (P < 0.05).

Conclusion:

Nigerian propolis contains compounds exhibiting hypoglycemic, antihyperlipidemic, and HbA1c reducing activities.

Bioactive Components of Chinese Propolis Water Extract on Antitumor Activity and Quality Control

To understand the material basis of antitumor activity of Chinese propolis water extract (CPWE), we developed a simple and efficient method using macroporous absorptive resin coupled with preparative high performance liquid chromatography and separated and purified eleven chemical components (caffeic acid, ferulic acid, isoferulic acid, 3,4-dimethoxycinnamic acid, pinobanksin, caffeic acid benzyl ester, caffeic acid phenethyl ester, apigenin, pinocembrin, chrysin, and galangin) from CPWE; then we tested the antitumor activities of these eleven components using different human tumor cell lines (MCF-7, MDA-MB-231, HeLa, and A549). Furthermore, cell migration, procaspase 3 level, and reactive oxygen species (ROS) of effective components from CPWE were investigated. Our data showed that antitumor activities of the eleven components from CPWE were different from each other. CPWE and its effective components induced apoptosis by inhibiting tumor cell migration, activating caspase 3, and promoting ROS production. It can be deduced that the antitumor effects of propolis did not depend on a single component, and there must exist "bioactive components," which also provides a new idea for Chinese propolis quality control.

Effects of seasonal variations and collection methods on the mineral composition of propolis from Apis mellifera Linnaeus Beehives

The effects of seasonal variations and the methods of collection of propolis produced by Africanized honey bees Apis mellifera Linnaeus, 1758, on the composition of constituent minerals such as magnesium (Mg), zinc (Zn), iron (Fe), sodium (Na), calcium (Ca), copper (Cu), and potassium (K) were evaluated. Propolis was harvested from 25 beehives by scraping or by means of propolis collectors (screen, "intelligent" collector propolis [ICP], lateral opening of the super [LOS], and underlay method). During the one-year study, the propolis produced was harvested each month, ground, homogenized, and stored in a freezer at -10 ºC. Seasonal analyses of the mineral composition were carried out by atomic absorption spectrophotometry and the results were evaluated by analysis of variance (ANOVA), followed by Tukey-Kramer's test to compare the mean values (p<0.05). The results showed that seasonal variations influence the contents of 5 minerals (Mg, Fe, Na, Ca, and Cu), and the propolis harvesting method affects the contents of 4 minerals (Mg, Zn, Fe, and Ca).

Relationship between total phenolic contents and biological properties of propolis from 20 different regions in South Korea

Background

Propolis (or bee glue), collected from botanical sources by honey bee, has been used as a popular natural remedies in folk medicine throughout the world. This study was conducted to assess growth inhibitory effects of ethanol extracts of propolis (EEPs) from 20 different regions in South Korea on human intestinal bacteria as well as their human β-amyloid precursor cleavage enzyme (BACE-1), acetylcholinesterase (AChE) inhibitory, antioxidant, antiproliferative, and anti-human rhinovirus activities.

Methods

The Bonferroni multiple-comparison method was used to test for significant differences in total polyphenol and flavonoid contents among EEP samples using SAS 9.13 program. Correlation coefficient (r) analysis of the biological activities of EEP samples was determined using their 50 % inhibition concentration or minimal inhibitory concentration values and their polyphenol or flavonoid contents in 20 native Korean EEP samples.

Results

The amounts of total polyphenol and flavonoids in the Korean EEP samples ranged from 49 to 239 mg gallic acid equivalent (GAE)/g EEP (Brazilian, Chinese, and Australian samples, 127–142 mg GAE/g EEP) and from 21 to 50 mg quercetin equivalent (QE)/g EEP (Brazilian, Chinese, and Australian samples, 33–53 mg QE/g EEP), respectively. Correlation coefficient analysis showed that total polyphenol contents may be negatively correlated with 2,2-diphenyl-1-picrylhydrazyl free radical scavenging activity (r = −0.872) and total flavonoid content has no correlation with the activity (r = 0.071). No direct correlation between BACE-1 inhibition, AChE inhibition, or antiproliferative activity and total polyphenol or total flavonoid content in Korean EEP samples was found. Gram-positive and Gram-negative bacteria were observed to have different degrees of antimicrobial susceptibility to the EEP samples examined, although ciprofloxacin susceptibility among the bacterial groups did not differ greatly.

Conclusions

Further studies will warrant possible applications of propolis as potential therapeutic BACE-1 blocker, antioxidant, antiproliferative agent, and antimicrobial agent.

Antiviral Activity of Hatay Propolis Against Replication of Herpes Simplex Virus Type 1 and Type 2

Background

Propolis is a bee product widely used in folk medicine and possessing many pharmacological properties. In this study we aimed to investigate: i) the antiviral activities of Hatay propolis samples against HSV-1 and HSV-2 in HEp-2 cell line, and ii) the presence of the synergistic effects of propolis with acyclovir against these viruses.

Material/Methods

All experiments were carried out in HEp-2 cell cultures. Proliferation assays were performed in 24-well flat bottom microplates. We inoculated 1×10⁵ cells per ml and RPMI 1640 medium with 10% fetal calf serum into each well. Studies to determine cytotoxic effect were performed. To investigate the presence of antiviral activity of propolis samples, different concentrations of propolis (3200, 1600, 800, 400, 200, 100, 75, 50, and 25 μg/mL) were added into the culture medium. The amplifications of HSV-1 and HSV-2 DNA were performed by real-time PCR method. Acyclovir (Sigma, USA) was chosen as a positive control. Cell morphology was evaluated by scanning electron microscopy (SEM).

Results

The replication of HSV-1 and HSV-2 was significantly suppressed in the presence of 25, 50, and 100 μg/mL of Hatay propolis. We found that propolis began to inhibit HSV-1 replication after 24 h of incubation and propolis activity against HSV-2 was found to start at 48 h following incubation. The activity of propolis against both HSV-1 and HSV-2 was confirmed by a significant decrease in the number of viral copies.

Conclusions

We determined that Hatay propolis samples have important antiviral effects compared with acyclovir. In particular, the synergy produced by antiviral activity of propolis and acyclovir combined had a stronger effect against HSV-1 and HSV-2 than acyclovir alone.

Caffeic acid phenethyl ester activates pro-apoptotic and epithelial-mesenchymal transition-related genes in ovarian cancer cells A2780 and A2780cis

Ovarian cancer is a highly aggressive pathology, displaying a poor prognosis and chemoresistance to classical therapy. The present study was conducted to evaluate the effect of caffeic acid phenethyl ester (CAPE) on survival of ovarian cancer cell lines, A2780 (sensitive to cisplatin) and A2780cis (resistant to cisplatin). MTT assay was used to evaluate cell viability, while the apoptotic processes were examined by flow cytometry and qRT-PCR. A reduction of cell proliferation and activation of the apoptosis was observed in both cell lines. qRT-PCR evaluation demonstrated the activation of the pro-apoptotic genes (BAD, CASP8, FAS, FADD, p53) in both cell lines. The limited therapeutic effect in A2780 cells is explained by the activation of epithelial-mesenchymal transition-related genes (ZEB1, ZEB2, or TGFBB1) as displayed by Ingenuity Network analysis. Overall data suggest that CAPE can be used as an alternative in sensitizing cells to chemotherapy.

Influence of Temperature on Free Radical Generation in Propolis-Containing Ointments

Free radicals thermally generated in the ointments containing propolis were studied by electron paramagnetic resonance (EPR) spectroscopy. The influence of temperature on the free radical concentration in the propolis ointments was examined. Two ointment samples with different contents of propolis (5 and 7%, resp.) heated at temperatures of 30°C, 40°C, 50°C, and 60°C, for 30 min., were tested. Homogeneously broadened EPR lines and fast spin-lattice interactions characterized all the tested samples. Free radicals concentrations in the propolis samples ranged from 10¹⁸ to 10²⁰ spin/g and were found to grow in both propolis-containing ointments along with the increasing heating temperature. Free radical concentrations in the ointments containing 5% and 7% of propolis, respectively, heated at temperatures of 30°C, 40°C, and 50°C were only slightly different. Thermal treatment at the temperature of 60°C resulted in a considerably higher free radical formation in the sample containing 7% of propolis when related to the sample with 5% of that compound. The EPR examination indicated that the propolis ointments should not be stored at temperatures of 40°C, 50°C, and 60°C. Low free radical formation at the lowest tested temperatures pointed out that both examined propolis ointments may be safely stored up to the temperature of 30°C.

Poplar-type Propolis: Chemical Composition, Botanical Origin and Biological Activity

Propolis is one of the most used natural products known for centuries for its beneficial effects. Due to significant differences in chemical composition of samples originating from different geographic and climatic zones it is crucial to characterize reliably each type of propolis. This article comprises the latest findings concerning the poplar type propolis, i.e. it gives a cross section of chemical composition, botanical origin and biological activity of poplar type propolis in order to encourage further investigations that would indicate its beneficial effects.

Caffeic acid phenethyl ester inhibits 3-MC-induced CYP1A1 expression through induction of hypoxia-inducible factor-1α

Caffeic acid phenethyl ester (CAPE), a natural component of propolis, is reported to have anticarcinogenic properties, although its precise chemopreventive mechanism remains unclear. In this study, we examined the effects of CAPE on 3-methylcholanthrene (3-MC)-induced CYP1A1 expression and activities. CAPE reduced the formation of the benzo[a]pyrene-DNA adduct. Moreover, CAPE inhibited 3-MC-induced CYP1A1 activity, mRNA expression, protein level, and promoter activity. CAPE treatment also decreased 3-MC-inducible xenobiotic-response element (XRE)-linked luciferase, aryl hydrocarbons receptor (AhR) transactivation and nuclear localization. CAPE induced hypoxia inducible factor-1α (HIF-1α) protein level and HIF-1α responsible element (HRE) transcriptional activity. CAPE-mediated HIF-1α reduced 3-MC-inducible CYP1A1 protein expression. Taken together, CAPE decreases 3-MC-mediated CYP1A1 expression, and this inhibitory response is associated with inhibition of AhR and HIF-1α induction.

Propolis: a new frontier for wound healing?

Propolis is a resin produced by honeybees by mixing wax, pollen, salivary secretions, and collected natural resins.

The precise composition of propolis varies with the source, and over 300 chemical components belonging to the flavonoids, terpenes, and phenolic acids have been identified in propolis. Moreover, its chemical composition is subjected to the geographical location, botanical origin, and bee species.

Propolis and its compounds have been the focus of many works due to their antimicrobial and anti-inflammatory activity; however, it is now recognized that propolis also possesses regenerative properties.

There is an increasing interest in the healing potential of natural products, considering the availability and low cost of these products. Propolis contains a huge number of compounds that explicate some biological effects that speeds up the healing process and is widely used in folk remedies.

This review aims to condense the results on the mechanism of activity of propolis and its compounds.

Antibiofilm Activity of Chilean Propolis on Streptococcus mutans Is Influenced by the Year of Collection

The chemical composition of propolis varies according to factors that could have an influence on its biological properties. Polyphenols from propolis have demonstrated an inhibitory effect on Streptococcus mutans growth. However, it is not known if different years of propolis collection may affect its activity. We aimed to elucidate if the year of collection of propolis influences its activity on Streptococcus mutans. Polyphenol-rich extracts were prepared from propolis collected in three different years, characterized by LC-MS and quantified the content of total polyphenols and flavonoids groups. Finally, was evaluated the antibacterial effect on Streptococcus mutans and the biofilm formation. Qualitative differences were observed in total polyphenols, flavones, and flavonols and the chemical composition between the extracts, affecting the strength of inhibition of biofilm formation but not the antimicrobial assays. In conclusion, chemical composition of propolis depends on the year of collection and influences the strength of the inhibition of biofilm formation.

Antiviral Action of Hydromethanolic Extract of Geopropolis from Scaptotrigona postica against Antiherpes Simplex Virus (HSV-1)

The studies on chemical composition and biological activity of propolis had focused mainly on species Apis mellifera L. (Hymenoptera: Apidae). There are few studies about the uncommon propolis collected by stingless bees of the Meliponini tribe known as geopropolis. The geopropolis from Scaptotrigona postica was collected in the region of Barra do Corda, Maranhão state, Brazil. The chemical analysis of hydromethanolic extract of this geopropolis (HMG) was carried out through HPLC-DAD-ESI-MS/MS and the main constituents found were pyrrolizidine alkaloids and C-glycosyl flavones. The presence of alkaloids in extracts of propolis is detected for the first time in this sample. The antiviral activity of HMG was evaluated through viral DNA quantification experiments and electron microscopy experiments. Quantification of viral DNA from herpes virus showed reduction of about 98% in all conditions and concentration tested of the HMG extract. The results obtained were corroborated by transmission electron microscopy, in which the images did not show particle or viral replication complex. The antiviral activity of C-glycosyl flavones was reported for a variety of viruses, being observed at different points in the viral replication. This work is the first report about the antiviral activity of geopropolis from Scaptotrigona postica, in vitro, against antiherpes simplex virus (HSV).