Cytotoxicity mechanisms in melanoma cells and UPLC-QTOF/MS2 chemical characterization of two Brazilian stingless bee propolis: Uncommon presence of piperidinic alkaloids

Chemical Profile and Biological Potential of Scaptotrigona Bee Products (Hymenoptera, Apidae, Meliponini): An Review

Stingless bees belong to the Meliponini tribe and are widely distributed in the tropics and subtropics, where they perform important ecological services. Among the best distributed groups of stingless bees is the genus Scaptotrigona, which includes 22 species distributed throughout the neotropical region, including the area from Mexico to Argentina. Bees of this genus are responsible for the production of products such as honey, propolis, geopropolis and fermented pollen ("saburá"). This review aimed to provide an overview of the chemical composition and biological activities associated with derived products from stingless bees of the genus Scaptotrigona. The bibliographic review was carried out through searches in the Scopus, Web of Science, ScienceDirect and PubMed databases, including publications from 2003 to January 2023. The study of the chemodiversity of products derived from Scaptotrigona demonstrated the mainly presence of flavonoids, phenolic acids, terpenoids and alkaloids. It was also demonstrated that products derived from bees of the genus Scaptotrigona exhibit a wide range of biological effects, such as antibacterial, antioxidant, anti-inflammatory and antifungal activities, among other bioactivities. This review provides an overview of phytochemical and pharmacological investigations of the genus Scaptotrigona. However, it is essential to clarify the toxicity and food safety of these products.

Antibacterial and Toxic Activity of Geopropolis Extracts from Melipona subnitida (Ducke, 1910) (Hymenoptera: Apidae) and Scaptotrigona depilis (Moure, 1942) (Hymenoptera: Apidae)

Bacteria are associated with many infections that affect humans and present antibiotic resistance mechanisms, causing problems in health organisations and increased mortality rates. Therefore, it is necessary to find new antibacterial agents that can be used in the treatment of these microorganisms. Geopropolis is a natural product from stingless bees, formed by a mixture of plant resins, salivary secretions, wax and soil particles, the chemical composition of this natural product is diverse. Thus, this study aimed to evaluate antibacterial activity, antibiotic modulation and the toxicity of geopropolis extracts from the stingless bees, Melipona subnitida (Ducke, 1910) and Scaptotrigona depilis (Moure, 1942) against standard and multi-resistant Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa bacteria. Geopropolis samples were collected in a meliponary located in Camaragibe, Pernambuco, Brazil. To determine the Minimum Inhibitory Concentration (MIC) and antibiotic modulation we performed broth microdilution tests. Mortality tests were used to verify extract toxicity in the model Drosophila melanogaster. The microbiological tests showing that the M. subnitida extracts had better inhibitory effects compared to S. depilis, presenting direct antibacterial activity against standard and multi-resistant strains. The extracts potentialized antibiotic effects, suggesting possible synergy and did not present toxicity in the model used. The information obtained in this study highlights extracts as promising antibacterial agents and is the first study to evaluate bacterial activity in these extracts, in addition to verifying their modulating effects and determining toxicity in the model used.

Evaluation of the Chemical Profile and Antioxidant Capacity of Green, Brown, and Dark Propolis

The chemical composition of propolis varies between different types, due to the specific vegetation found near the hives and the climatic and soil conditions worldwide. Green propolis is exclusive to Brazil, produced by bees, with the resin of the plant Baccharis dracunculifolia. Brown propolis is a specific variety produced mainly in Northeast Brazil from the plant Hyptis divaricata, also known as "maria miraculosa". Dark propolis is a variety of propolis produced by bees from the resin of the plant known as Jurema Preta (Mimosa hostilis benth). In this study, the aqueous extracts of green, brown, and dark propolis were analyzed for their antioxidant capacity using ABTS, FRAP, and DPPH, and their chemical profiles were determined using paper spray mass spectrometry. Among the three extracts, green propolis had the highest content of total phenolic compounds (2741.71 ± 49.53 mg GAE. 100 g-1), followed by brown propolis (1191.55 ± 36.79 mg GAE. 100 g-1), and dark propolis had the lowest content (901.79 ± 27.80 mg GAE. 100 g-1). The three types of propolis showed high antioxidant capacity, with green showing the highest antioxidant capacity for the three methods used. Using paper spray mass spectrometry, it was possible to suggest the presence of 116 substances, including flavonoids (56), phenylpropanoids (30), terpenes (25), carboxylic acids (1), benzoic acid derivatives (1), fatty acids (1), amino acids (1) and alkaloids (1). The compounds in the green, brown, and dark propolis extracts reinforce the bioactive potential for application in these tree extracts' food and pharmaceutical products.

Antimicrobial Diterpenes from Rough Goldenrod (Solidago rugosa Mill.)

Solidago rugosa is one of the goldenrod species native to North America but has sporadically naturalized as an alien plant in Europe. The investigation of the root and leaf ethanol extracts of the plant using a bioassay-guided process with an anti-Bacillus assay resulted in the isolation of two antimicrobial components. Structure elucidation was performed based on high-resolution tandem mass spectrometric and one- and two-dimensional NMR spectroscopic analyses that revealed (-)-hardwickiic acid (Compound 1) and (-)-abietic acid (Compound 2). The isolates were evaluated for their antimicrobial properties against several plant pathogenic bacterial and fungal strains. Both compounds demonstrated an antibacterial effect, especially against Gram-positive bacterial strains (Bacillus spizizenii, Clavibacter michiganensis subsp. michiganensis, and Curtobacterium flaccumfaciens pv. flaccumfaciens) with half maximal inhibitory concentration (IC₅₀) between 1 and 5.1 µg/mL (5-20 times higher than that of the positive control gentamicin). In the used concentrations, minimal bactericidal concentration (MBC) was reached only against the non-pathogen B. spizizenii. Besides their activity against Fusarium avenaceum, the highest antifungal activity was observed for Compound 1 against Bipolaris sorokiniana with an IC₅₀ of 3.8 µg/mL.

Phenolic Compounds Contribution to Portuguese Propolis Anti-Melanoma Activity

Melanoma is the deadliest type of skin cancer, with about 61,000 deaths annually worldwide. Late diagnosis increases mortality rates due to melanoma’s capacity to metastasise rapidly and patients’ resistance to the available conventional therapies. Consequently, the interest in natural products as a strategy for drug discovery has been emerging. Propolis, a natural product produced by bees, has several biological properties, including anticancer effects. Propolis from Gerês is one of the most studied Portuguese propolis. Our group has previously demonstrated that an ethanol extract of Gerês propolis collected in 2018 (G18.EE) and its fractions (n-hexane, ethyl acetate, and n-butanol) decrease melanoma cell viability. Out of all the fractions, G18.EE-n-BuOH showed the highest potential as a melanoma pharmacological therapy. Thus, in this work, G18.EE-n-BuOH was fractioned into 17 subfractions whose effect was evaluated in A375 BRAF-mutated melanoma cells. The subfractions with the highest cytotoxic activity were analysed by UPLC-DAD-ESI/MSn in an attempt to understand which phenolic compounds could account for the anti-melanoma activity. The compounds identified are typical of the Gerês propolis, and some of them have already been linked with antitumor effectiveness. These results reaffirm that propolis compounds can be a source of new drugs and the isolation of compounds could allow its use in traditional medicine.

The Role of Propolis as a Natural Product with Potential Gastric Cancer Treatment Properties: A Systematic Review

Gastric cancer is one of the most common, aggressive, and invasive types of malignant neoplasia. It ranks fifth for incidence and fourth for prevalence worldwide. Products of natural origin, such as propolis, have been assessed for use as new complementary therapies to combat cancer. Propolis is a bee product with antiproliferative and anticancer properties. The concentrations and types of secondary metabolites contained in propolis mainly vary according to the geographical region, the season of the year, and the species of bees that make it. The present study is a systematic review of the main articles related to the effects of propolis against gastric cancer published between 2011 and 2021 in the PubMed and Science Direct databases. Of 1305 articles published, only eight studies were selected; among their principal characteristics was the use of in vitro analysis with cell lines from gastric adenocarcinoma and in vivo murine models of the application of propolis treatments. These studies suggest that propolis arrests the cell cycle and inhibits proliferation, prevents the release of oxidizing agents, and promotes apoptosis. In vivo assays showed that propolis decreased the number of tumors by regulating the cell cycle and the expression of proteins related to apoptosis.

A review of stingless bees' bioactivity in different parts of the world

Stingless bees, also known as meliponines, live in beehives. However, reports on the distribution of stingless bees are scattered, resulting in a lack of precision. Honey and propolis are the main components that can be harvested from their beehive, with a great commercial value of up to 610 million USD. Despite the enormous potential profits, discrepancies in their bioactivities have been observed worldwide, leading to a lack of confidence. Therefore, this review provided oversight on the potential of stingless bee products and highlighted the differences between stingless bees in Asia, Australia, Africa, and America. The bioactivity of stingless bee products is diverse and exhibits great potential as an antimicrobial agent or in various diseases such as diabetes, cardiovascular disease, cancers, and oral problems.

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

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

Plant genetic diversity by DNA barcoding to investigate propolis origin

Identify the botanical origins of a certain type of propolis may be challenging and time demanding, since it involves bee's behavior observation, plant resins collection and chemical analysis. Thus, this study aimed to determine the plant genetic materials in propolis from southern Brazil using the DNA barcoding to investigate their botanical origins, as well as to compare it with the phytochemical composition determined by ultra-high-performance liquid chromatography coupled with high-resolution mass spectrometry (UHPLC-HRMS) and with the pollinic profile. As principal results, non-native Populus carolinensis Moench (Salicaceae) was almost the only DNA source in some propolis samples, which coincided with the presence of flavonoids typical from poplar exudates. Conversely, other propolis samples had DNA material coming mainly from native plant species, most of them characterized to the species level, although no specific chemical markers from those plants could be identified by UHPLC-HRMS. However, pollen from several plants identified by the DNA barcoding were extracted from some propolis samples. Despite the identification of typical diterpenes, DNA material from Araucaria angustifolia (Bertol.) Kuntze (Araucariaceae), which have been indicated as a major resin source for propolis from preservation areas in southern Brazil, was found in very small abundancies, likely because bees do not drag tissue material containing DNA when collecting resin from this native species. In conclusion, DNA barcoding analysis successfully provided information about the provenance of propolis, although, depending on the plant resin sources, this information is likely to come from pollen.

Portuguese Propolis Antitumoral Activity in Melanoma Involves ROS Production and Induction of Apoptosis

Melanoma is the most aggressive and life-threatening skin cancer type. The melanoma genome is the most frequently mutated, with the BRAF mutation present in 40–60% of melanoma cases. BRAF-mutated melanomas are characterized by a higher aggressiveness and progression. Adjuvant targeted treatments, such as BRAF and MEK inhibitors, are added to surgical excision in BRAF-mutated metastatic melanomas to maximize treatment effectiveness. However, resistance remains the major therapeutic problem. Interest in natural products, like propolis, for therapeutic applications, has increased in the last years. Propolis healing proprieties offer great potential for the development of novel cancer drugs. As the activity of Portuguese propolis has never been studied in melanoma, we evaluated the antitumoral activity of propolis from Gerês (G18.EE) and its fractions (n-hexane, ethyl acetate (EtOAc), and n-butanol) in A375 and WM9 melanoma cell lines. Results from DPPH•/ABTS• radical scavenging assays indicated that the samples had relevant antioxidant activity, however, this was not confirmed in the cell models. G18.EE and its fractions decreased cell viability (SRB assay) and promoted ROS production (DHE/Mitotracker probes by flow cytometry), leading to activation of apoptotic signaling (expression of apoptosis markers). Our results suggest that the n-BuOH fraction has the potential to be explored in the pharmacological therapy of melanoma.

13C Natural Isotope Abundance in Urothelium as a New Marker in the Follow-Up of Patients with Bladder Cancer

Bladder cancer (BC) is the most common urological malignancy and has a high incidence of recurrence. BC cells alter their nutrient uptake and metabolic pathways in order to continue the production of sufficient levels of ATP and metabolic intermediates for proliferation and survival. Changes in metabolic pathways regarding the rate of the enzymatic reaction and transport lead to differences in the content of natural isotopes (13C, 15N, 34S) between normal and cancerous tissues. The assessment of the stable isotopes of carbon, nitrogen, and sulfur in normal urothelium and bladder cancer samples was performed using Isotope Ratio Mass Spectrometry (IRMS). The natural abundance of 15N and 13C was decreased in bladder cancer samples when compared to normal urothelium. No significant correlation was observed in BC specimens depending on the tumor grade and stage. Samples derived from bladder tumors and normal urothelium had a different pattern of 15N and 13C isotope abundance. Decreased 13C natural isotopes in the normal urothelium of BC patients were significantly associated with a shorter DFS. Our results suggest that isotopic analysis of normal urothelium of BC patients can be used to predict bladder cancer recurrence.

Ethanol-Extracted Cameroonian Propolis Counteracts Tamoxifen-Induced Endometrial Hyperplasia by Modulating Apoptosis and Proliferation-Regulating Proteins in the Ovaries of Intact Wistar Rats

Tamoxifen is the most common adjuvant that has been widely used in the treatment of positive estrogen receptor (ER+) breast cancer for over 20 years. However, long term exposure to tamoxifen doubles the risk of endometrial cancer. The association of tamoxifen with antiproliferative substances could abrogate its side effects on the endometrium. Recently, we demonstrated that ethanol-extracted Cameroonian propolis (EECP) has chemopreventive effects on ER+ breast cancer in rats. This study evaluated the capability of EECP to counteract tamoxifen-induced endometrial hyperplasia, without altering its effect on the breast. Thirty-six rats of ∼2 months were coadministered either EECP (16.5, 50, and 150 mg/kg BW) or fulvestrant (300 μg/kg BW) and tamoxifen (10 mg/kg BW) for 8 weeks. Afterward, the relative weights and histomorphometry of the uterus, vagina, ovaries, and mammary gland were assessed. The expression of some proteins of proliferation (PCNA), angiogenesis (VEGF), and apoptosis (Bax, Bcl-2, and caspase-3) was measured by immunohistochemistry. Rats that received only tamoxifen had endometrial hyperplasia compared to normal rats. EECP and fulvestrant protected the rats against tamoxifen-induced endometrial hyperplasia. A significant decrease in uterine wet weight ( $p<0.01$ ); endometrial height ( $p<0.001$ ); and expression of PCNA, Bcl-2, and VEGF proteins as well as a significant increase in the expression of Bax and caspase-3 proteins was observed in the EECP group compared to the Tamox group. EECP did not change the effects of tamoxifen on the breast. In summary, Cameroonian propolis which is efficacious in preventing breast cancer can also be a good complementary medicine to prevent tamoxifen-induced endometrial cancer in tamoxifen users.

Bis-nor-diterpene from Cnidoscolus quercifolius (Euphorbiaceae) induces tubulin depolymerization-mediated apoptosis in BRAF-mutated melanoma cells

A phytochemical investigation of cytotoxic extract and fractions of Cnidoscolus quercifolius Pohl led to isolation of five terpenoids, including three lupane-type triterpenes (1-3) and two bis-nor-diterpenes (4-5). Compounds 4 (phyllacanthone) and 5 (favelanone) are commonly found in this species and have unique chemical structure. Although their cytotoxic activity against cancer cells has been previously reported, the anticancer potential of these molecules remains poorly explored. In this paper, the antimelanoma potential of phyllacanthone (PHY) was described for the first time. Cell viability assay showed a promising cytotoxic activity (IC₅₀ = 40.9 μM) against chemoresistant human melanoma cells expressing the BRAF oncogenic mutation (A2058 cell line). After 72 h of treatment, PHY inhibited cell migration and induced apoptosis and cell cycle arrest (p < 0.05). Immunofluorescence assay showed that the pro-apoptotic effect of PHY is probably associated with tubulin depolymerization, resulting in cytoskeleton disruption of melanoma cells. Molecular docking investigation confirmed this hypothesis given that satisfactory interaction between PHY and tubulin was observed, particularly at the colchicine binding site. These results suggest PHY from C. quercifolius could be potential leader for the design of new antimelanoma drugs.

Cytotoxicity effect of honey, bee pollen, and propolis from seven stingless bees in some cancer cell lines

Our effort to find new material for anti cancer from natural resources leads us to focus on stingless bee products such as honey, bee pollen, and propolis. The products were from seven stingless bees named Homotrigona fimbriata, Heterotrigona itama, Heterotrigona bakeri, Tetragonula sarawakensis, Tetragonula testaceitarsis, Tetragonula fuscobalteata, Tetragonula laeviceps. The stingless bee products were evaluated for their cytotoxicity effect on MCF-7, HeLa and Caco-2 cancer cell lines. This is the first time to be reported that the honey, ethanol extracts of bee pollen and propolis of H. fimbriata displayed more potent cytotoxicity than other stingless bee products. By chromatography and biological activity-guided fractionation, ethanol extract of propolis from H. fimbriata was fractionated and isolated its active compound named mangiferonic acid. Mangiferonic acid showed a cytotoxicity effect with IC₅₀ values 96.76 µM in MCF-7, >110.04 µM in HeLa, and > 110.04 µM in Caco-2, respectively. These results exhibited the potential of ethanol extracts from propolis of H. fimbriata to be further developed for drug and experiments to verify the function are essential.

Use of Stingless Bee Propolis and Geopropolis against Cancer-A Literature Review of Preclinical Studies

Cancer is one of the major maladies affecting humankind and remains one of the leading causes of death worldwide. The investigation of the biological activities of stingless bee products, especially propolis and geopropolis, has revealed promising therapeutic properties, especially in the research on new antineoplastic agents. This literature review of preclinical trials, involving biological assays of antitumor activity and identification of the chemical composition of propolis and geopropolis of stingless bee species, describes the cytotoxicity in tumor lineages (breast, lung, ovarian, liver, mouth, pharynx, larynx, colon, stomach, colorectal, cervix, kidney, prostate, melanoma, human glioblastoma, canine osteosarcoma, erythroleukemia, human chronic myelocytic leukemia, and human promyelocytic leukemia) of propolis and geopropolis of 33 species of stingless bees. The chemical composition of propolis and geopropolis was identified, indicating that these belong to the chemical classes of phenolic acids, flavonoids, coumarins, benzophenones, anthraquinones, alkaloids, terpenes, steroids, saponins, fatty acids, and carbohydrates and are possibly responsible for the cytotoxicity in tumor cells. Apoptosis was one of the main mechanisms of cytotoxicity of extracts and substances isolated from stingless bee products. Although the results found are encouraging, other preclinical studies and clinical trials are essential for the discovery of new anticancer agents.

Stingless Bee Propolis: New Insights for Anticancer Drugs

Natural products are important sources of biomolecules possessing antitumor activity and can be used as anticancer drug prototypes. The rich biodiversity of tropical and subtropical regions of the world provides considerable bioprospecting potential, including the potential of propolis produced by stingless bee species. Investigations of the potential of these products are extremely important, not only for providing a scientific basis for their use as adjuvants for existing drug therapies but also as a source of new and potent anticancer drugs. In this context, this article organizes the main studies describing the anticancer potential of propolis from different species of stingless bees with an emphasis on the chemical compounds, mechanisms of action, and cell death profiles. These mechanisms include apoptotic events; modulation of BAX, BAD, BCL2-L1 (BCL-2 like 1), and BCL-2; depolarization of the mitochondrial membrane; increased caspase-3 activity; poly (ADP-ribose) polymerase (PARP) cleavage; and cell death induction by necroptosis via receptor interacting protein kinase 1 (RIPK1) activation. Additionally, the correlation between compounds with antioxidant and anti-inflammatory potential is demonstrated that help in the prevention of cancer development. In summary, we highlight the important antitumor potential of propolis from stingless bees, but further preclinical and clinical trials are needed to explore the selectivity, efficacy, and safety of propolis.

Antiviral, Antibacterial, Antifungal, and Antiparasitic Properties of Propolis: A Review

Propolis is a complex phytocompound made from resinous and balsamic material harvested by bees from flowers, branches, pollen, and tree exudates. Humans have used propolis therapeutically for centuries. The aim of this article is to provide comprehensive review of the antiviral, antibacterial, antifungal, and antiparasitic properties of propolis. The mechanisms of action of propolis are discussed. There are two distinct impacts with regards to antimicrobial and anti-parasitic properties of propolis, on the pathogens and on the host. With regards to the pathogens, propolis acts by disrupting the ability of the pathogens to invade the host cells by forming a physical barrier and inhibiting enzymes and proteins needed for invasion into the host cells. Propolis also inhibits the replication process of the pathogens. Moreover, propolis inhibits the metabolic processes of the pathogens by disrupting cellular organelles and components responsible for energy production. With regard to the host, propolis functions as an immunomodulator. It upregulates the innate immunity and modulates the inflammatory signaling pathways. Propolis also helps maintain the host's cellular antioxidant status. More importantly, a small number of human clinical trials have demonstrated the efficacy and the safety of propolis as an adjuvant therapy for pathogenic infections.

Propolis of stingless bees: A phytochemist's guide through the jungle of tropical biodiversity

BACKGROUND

Stingless bees (Meliponini), like honeybees Apis mellifera, collect plant resins in order to produce propolis (cerumen, geopropolis). This type of propolis has long been used in traditional medicine in Mexico, Brazil, Argentina, India, and Vietnam, as a remedy for improving health and treating various diseases. The scientific and commercial interest in stingless bee propolis has been steadily increasing over the last few years. The new and growing knowledge in this field requires systematising, as a basis for further work. Recent reviews of Meliponini propolis deal only with the South American and Mesoamerican species, while reviews of the Asian, Australian and African species are missing. Furthermore, the chemical composition has not been thoroughly reviewed since 2007.

PURPOSE

This review summarises and discusses the available data about the chemical composition of propolis from the stingless bee species (Meliponinae) of the Americas, Asia and Australia, published after 2007. The published information on the biological action of chemically characterised Meliponini propolis, and of individual constituents, is addressed. The plant sources of this propolis are also considered.

CONCLUSION AND PERSPECTIVES

Chemical studies of Meliponini propolis has resulted in the discovery of new natural molecules, some of them with valuable bioactivity. Moreover, finding known molecules in propolis stimulates the study of their pharmacological properties. The enormous chemical variability of stingless bee propolis is a challenge to chemists, entomologists and pharmacologists. It is essential to perform pharmacological studies with only chemically characterised propolis of stingless bees. Further studies are required to chemically characterise and scientifically support the medicinal properties of stingless bee propolis and to clarify the potential for its commercial use. This could lead to increased prices for Meliponinae propolis and provide an additional source of income for farmers in rural communities with most serious social needs.

Propolis Extract Regulate microRNA Expression in Glioblastoma and Brain Cancer Stem Cells

BACKGROUND

Grade IV gliomas are classified as glioblastoma (GBM), which is the most malignant brain cancer type. Various genetic and epigenetic mechanisms play a role in the initiation and progression of GBM. MicroRNAs (miRNAs) are small, non-coding RNA molecules that are the main epigenetic regulatory RNA class. They play variable roles in both physiological and pathological conditions, including GBM pathogenesis, by regulating expression levels of the target genes. Brain cancer stem cells (BCSCs) are subpopulations of brain cancer mass that are responsible for poor prognosis, including therapy resistance and relapse. Epigenetic regulation mediated by miRNAs is also a critical component of BCSC self-renewal and differentiation properties. Propolis is a resinous substance that is collected by honey bees from various plant sources. The flavonoids content of propolis varies, depending on the region collected andthe extraction method. Although the effects of propolis that have been collected from different sources on the miRNA expression levels in the glioblastoma cells have been shown, the effects on the BCSCs are not known yet.

OBJECTIVE

The aim of this study is to evaluate the effects of Aydın, a city in western Turkey, propolis, on miRNA expression levels of BCSCs and GBM cells.

METHODS

Aydin propolis was dissolved in 60% ethanol, and after evaporation, distilled water was added to prepare the propolis stock solution. The flavonoids content of the Aydin propolis was determined by MS Q-TOF analysis. Commercially obtained U87MG, GBM cell line, and BCSCs were used as in vitro brain cancer models. The cytotoxic and apoptotic effects of Aydın propolis were determined via WST-1 assay and Annexin V test, respectively. The miRNA expression profile was investigated via the real-time qRT-PCR method, and fold changes were calculated by using the 2-^∆∆Ct method compared to untreated control cells. The miRNA-mRNA-pathway interactions, including significantly altered miRNAs, were determined using different bioinformatics tools and databases.

RESULTS

Quercetin 3-methyl ether was determined as the major component of the Aydin propolis. Aydin propolis did not show significant cytotoxic and apoptotic effects on both GBM and BCSCs up to 2mg/ml concentration. Aydin propolis treatment decreased the expression of nine and five miRNAs in the U87MG 2.13 to 5.65 folds and BCSCs 2.02 to 12.29 folds, respectively. Moreover, 10 miRNAs 2.22 to 10.56 folds were upregulated in propolis treated GBM cells compared to the control group, significantly (p<0.05). In the study, the potential roles of two new miRNAs, whose regulations in glioma were not previously defined, were identified. One of these miR-30d-5p, a novel potential oncomiR in GBM was 2.46 folds downregulated in Aydin propolis treated GBM cells. The other one is miR-335-5p which is a potential tumor suppressor miR in GBM, was 5.66 folds upregulated in Aydin propolis treated GBM cells. FOXO pathway and its upstream and downstream regulators and critically neuronal developmental regulators NOTCH and WNT pathways were determined as the most deregulated pathways in Aydin propolis treated cells.

CONCLUSION

The determination of the anti-cancer effect of Aydın propolis on the miRNA expression of GBM, especially on cancer stem cells, may contribute to the elucidation of brain cancer genetics by supporting further analyses.

The antimammary tumor effects of ethanolic extract of propolis from Adamawa region (Cameroon) are by apoptosis via reactive oxygen species-mediated mitochondrial pathway

Identification of novel natural treatment to combat cancer is a current need. This study was aimed at assessing the anticancer effects of ethanol-extracted Cameroonian propolis (EEP). The antitumor effect of EPP was evaluated in vitro by measuring; cell viability, cell cycle, cell death mechanism, cell migration/invasion, reactive oxygen species (ROS), mitochondrial potential (ΔΨm), caspase activity, and apoptosis-regulating proteins (Bcl-2 and Bcl-XL) in cell lines. In vivo, the effect of EEP against 7,12 dimethylbenz(a)anthracene (DMBA)-induced breast tumorigenesis in rats was assessed. EEP was found to induce cytotoxicity against ER negative MDA-MB-231 breast cancer cells by activating apoptosis through ROS-mediated mitochondrial pathway. The extract equally triggered caspase-3 and caspase-9, increment of ROS level, disruption of ΔΨm and down-regulation of Bcl-XL and Bcl-2 proteins. Besides, EPP prevented migration and invasion activities by inhibiting MMP-2 activity. At all doses it prevented breast tumor incidence (20% in EEP 150 mg/kg vs 70% in DMBA) as well as tumor burden. Tumor sections from EEP-treated rats showed middle proliferation of mammary ducts with weak inflammatory responses. In summary, Cameroonian propolis exhibited antimammary tumor effects via the intrinsic pathway of apoptosis.

Chemical composition, cytotoxicity, and antibacterial activity of propolis from Africanized honeybees and three different Meliponini species

ETHNOPHARMACOLOGICAL RELEVANCE

Propolis extracts are widely used in traditional folk medicine and exhibit several properties such as antitumor, anti-inflammatory, and antimicrobial. However, these products have not been investigated in combination with medicines used in clinical practice.

AIM OF THE STUDY

This study aimed to evaluate the chemical composition of propolis extracts from Apis mellifera scutellata and different Meliponini species and characterize their cytotoxicity against tumor cells, antibacterial effects, and interference with the actions of doxorubicin and gentamicin.

MATERIALS AND METHODS

Chromatographic and spectrometric analyses were performed using ultra-high-performance liquid chromatography (UPLC)-tandem mass spectrometry (MS/MS). Propolis extracts were evaluated for cytotoxicity and synergism using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and the antimicrobial activity was examined using the broth microdilution technique and synergism was investigated using checkerboard and time-kill assays.

RESULTS

The chemical characterization revealed the presence of 63 compounds, and the extracts showed selective cytotoxicity against tumor cell lines. Propolis extracts of mandaçaia and mirim exerted selective synergistic cytotoxicity in combination with doxorubicin. Except for the tubuna extract, all evaluated extracts exhibited antibacterial effects on gram-positive strains. Mandaçaia and mirim extracts exerted a synergistic effect with gentamicin; however, only mandaçaia extract exerted a selective effect.

CONCLUSION

Propolis could be a source of antineoplastics and antibiotics. These natural products may reduce the occurrence of doxorubicin and gentamicin related adverse effects, resistance, or both.

Abyssinone V-4' Methyl Ether, a Flavanone Isolated from Erythrina droogmansiana, Exhibits Cytotoxic Effects on Human Breast Cancer Cells by Induction of Apoptosis and Suppression of Invasion

Abyssinone V-4′ methyl ether (AVME) isolated from Erythrina droogmansiana was recently reported to exhibit anti-mammary tumor effect in mice. The present work was therefore aimed at elucidating its cellular and molecular mechanisms. To achieve our goal, the cytotoxicity of AVME against tumoral and non-tumoral cell lines was evaluated by resazurin reduction test; flow cytometry allowed us to evaluate the cell cycle and mechanisms of cell death; the mitochondrial transmembrane potential, reactive oxygen species (ROS) levels, and caspase activities as well as apoptosis-regulatory proteins (Bcl-2 and Bcl-XL) were measured in MDA-MB-231 cells. Further, the antimetastatic potential of AVME was evaluated by invasion assay. AVME exhibited cytotoxic effects in all tested tumor cell lines and induced a significant increase in the percentage of MDA-MB-231 cells at G2/M and S phases of the cell cycle in a concentration-dependent manner. AVME also induced apoptosis in MDA-MB-231 cells, which was accompanied by the activation of caspase-3 and caspase-9 and downregulation of Bcl-2 and Bcl-XL proteins. Moreover, AVME suppressed cancer cell invasion by the inhibition of the metalloproteinase-9 activity. Findings from this study suggest that AVME has anti-breast cancer activities expressed through mitochondrial proapoptotic pathway including impairment of aggressive behaviors of breast cancer cells.

Complexation with β-cyclodextrin enhances apoptosis-mediated cytotoxic effect of harman in chemoresistant BRAF-mutated melanoma cells

Harman, a natural β-carboline alkaloid, has recently gained considerable interest due to its anticancer properties. However, its physicochemical characteristics and poor oral bioavailability have been limiting factors for its pharmaceutical development. In this paper, we described the complexation of harman (HAR) with β-cyclodextrin (βCD) as a promising alternative to improve its solubility and consequently its cytotoxic effect in chemoresistant melanoma cells (A2058 cell line). Inclusion complexes (βCD-HAR) were prepared using a simple method and then characterized by FTIR, NMR and SEM techniques. Through in silico studies, the mechanism of complexation of HAR with βCD was elucidated in detail. Both HAR and βCD-HAR promoted cytotoxicity, apoptosis, cell cycle arrest and inhibition of cell migration in melanoma cells. Interestingly, complexation of HAR with βCD enhanced its pro-apoptotic effect by increasing of caspase-3 activity (p < 0.05), probably due to an improvement in HAR solubility. In addition, HAR and βCD-HAR sensitized A2058 cells to vemurafenib, dacarbazine and 5FU treatments, potentializing their cytotoxic activity. These findings suggest that complexation of HAR with natural polymers such as βCD can be useful to improve its bioavailability and antimelanoma activity.

Antioxidant-Based Medicinal Properties of Stingless Bee Products: Recent Progress and Future Directions

Stingless bees are a type of honey producers that commonly live in tropical countries. Their use for honey is being abandoned due to its limited production. However, the recent improvements in stingless bee honey production, particularly in South East Asia, have brought stingless bee products back into the picture. Although there are many stingless bee species that produce a wide spread of products, known since old eras in traditional medicine, the modern medical community is still missing more investigational studies on stingless bee products. Whereas comprehensive studies in the current era attest to the biological and medicinal properties of honeybee (Apis mellifera) products, the properties of stingless bee products are less known. This review highlights for the first time the medicinal benefits of stingless bee products (honey, propolis, pollen and cerumen), recent investigations and promising future directions. This review emphasizes the potential antioxidant properties of these products that in turn play a vital role in preventing and treating diseases associated with oxidative stress, microbial infections and inflammatory disorders. Summarizing all these data and insights in one manuscript may increase the commercial value of stingless bee products as a food ingredient. This review will also highlight the utility of stingless bee products in the context of medicinal and therapeutic properties, some of which are yet to be discovered.

Mediterranean Propolis from the Adriatic Sea Islands as a Source of Natural Antioxidants: Comprehensive Chemical Biodiversity Determined by GC-MS, FTIR-ATR, UHPLC-DAD-QqTOF-MS, DPPH and FRAP Assay

There is no systematic report about propolis chemical biodiversity from the Adriatic Sea islands affecting its antioxidant capacity. Therefore, the samples from the islands Krk, Rab, Pag, Biševo and Korčula were collected. Comprehensive methods were used to unlock their chemical biodiversity: headspace solid-phase microextraction (HS-SPME) and hydrodistillation (HD) followed by gas chromatography and mass spectrometry (GC-MS); Fourier transform mid-infrared spectroscopy (FT-MIR); ultra high performance liquid chromatography with diode array detector and quadrupole time-of-flight mass spectrometry (UHPLC-DAD-QqTOF-MS) and DPPH and FRAP assay. The volatiles variability enabled differentiation of the samples in 2 groups of Mediterranean propolis: non-poplar type (dominated by α-pinene) and polar type (characterized by cadinane type sesquiterpenes). Spectral variations (FT-MIR) associated with phenolics and other balsam-related components were significant among the samples. The UHPLC profiles allowed to track compounds related to the different botanical sources such as poplar (pinobanksin esters, esters and glycerides of phenolic acids, including prenyl derivatives), coniferous trees (labdane, abietane diterpenes) and Cistus spp. (clerodane and labdane diterpenes, methylated myricetin derivatives). The antioxidant potential determined by DPPH ranged 2.6-81.6 mg GAE/g and in FRAP assay 0.1-0.8 mmol Fe2+/g. The highest activity was observed for the samples of Populus spp. origin. The antioxidant potential and phenolic/flavonoid content was positively, significantly correlated.