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Propolis is very popular for its beneficial health properties, such as antimicrobial activity and antioxidant effects. It is one of the most long-serving traditional medicines to mankind due to its interesting chemical diversity and therapeutic properties. The detailed chemical information of propolis samples is very necessary to guarantee its safety and for it to be accepted into health care systems. The phenolic profile of the hydroethanolic extract was determined using HPLC-DAD, and the antioxidant was evaluated using five complementary methods. Triterpenoids were isolated using column chromatography and characterized using 1H NMR and 13C NMR. The effects of the extract and the isolated compounds on quorum sensing mediated processes and biofilm formation in bacteria were evaluated. Protocatechic acid (40.76 ± 0.82 µg/g), 4-hydroxybenzoic acid (24.04 ± 0.21 µg/g), vanillic acid (29.90 ± 1.05 µg/g), quercetin (43.53 ± 1.10 µg/g), and luteolin (4.44 ± 0.48 µg/g) were identified and quantified. The extract showed good antioxidant activity in the DPPH•, ABTS•+, CUPRAC, and metal chelating assays, and this antioxidant effect was confirmed by cyclic voltammetry. 27-Hydroxymangiferonic acid (1), Ambolic acid (2), and Mangiferonic acid (3) were isolated from anti-quorum sensing activity at MIC, and it was indicated that the most active sample was the extract with inhibition diameter zone of 18.0 ± 1.0 mm, while compounds 1, 2, and 3 had inhibition zones of 12.0 ± 0.5 mm, 9.0 ± 1.0 mm, and 12.3 ± 1.0 mm, respectively. The samples inhibited the P. aeruginosa PA01 swarming motility at the three tested concentrations (50, 75, and 100 μg/mL) in a dose-dependent manner. The propolis extract was able to inhibit biofilm formation by S. aureus, E. coli, P. aeruginosa, C. albicans, and C. tropicalis at MIC concentration. Compound 1 proved biofilm inhibition on S. aureus, L. monocytogenes, E. faecalis, E. coli, and C. tropicalis at MIC and MIC/2; compound 2 inhibited the formation of biofilm at MIC on S. aureus, E. faecalis, E. coli, S. typhi, C. albicans, and C. tropicalis; and compound 3 inhibited biofilm formation on E. faecalis, E. coli, C. albicans, and C. tropicalis and further biofilm inhibition on E. coli at MIC/4 and MIC/8. The studied propolis sample showed important amounts of cycloartane-type triterpene acids, and this indicates that there can be significant intra-regional variation probably due to specific flora within the vicinity. The results indicate that propolis and its compounds can reduce virulence factors of pathogenic bacteria.

Recently, the honey and propolis of stingless bees have been attracting growing atten-tion because of their health-promoting properties. However, studies on these products of African Meliponini are still very scarce. In this preliminary study, we analyzed the chemical composition of honey, two cerumen, and two resin deposits (propolis) samples of Meliponula ferruginea from Tanzania. The honey of M. ferruginea was profiled by NMR and indicated different long-term stability from Apis mellifera European (Bulgarian) honey. It differed significantly in sugar and organic acids content and had a very high amount of the disaccharide trehalulose, known for its bioactivities. We suggested trehalulose to be a potential marker for African stingless bee honey analogously to the recent proposal for Meliponini honey from Asia, South America, and Australia and demonstrated its easy discrimination by13 C NMR. Propolis and cerumen were studied by GC-MS (gas chromatography-mass spectometry). The samples contained mainly terpenoids (di-and triterpenes) but demonstrated qualitative and quantitative differences. This fact was an indication that possibly M. ferruginea has no strict preferences for resins used to construct and protect their nests. The an-timicrobial and anti-quorum sensing properties of the two materials were also tested. These first results demonstrated that the honey, cerumen, and propolis of African stingless bees were rich in biologically active substances and deserved further research Funding: This research was partially supported by the Bulgarian Ministry of Education and Science under the National Research Program “Healthy Foods for a Strong Bio-Economy and Quality of Life,” approved by DCM # 577/17.08.2018. The financial support for the NMR spectrometer of the Bulgarian National Science Fund (UNA-17/2005, DRNF-02-13/2009) and the Ministry of Education and Science-Bulgaria (INFRAMAT project) is gratefully acknowledged.

Quorum Sensing is a special system between bacteria to communicate with the signal molecules. Propolis is a resin collected from plants by honey bees. The present study examined anti-quorum sensing and antimicrobial activities of water and ethanol extracts of propolis. The antimicrobial activities of the propolis extracts were studied against Escherichia coli ATCC 25922 Gram (-), Listeria monocytogenes ATCC 7644, Streptococcus mutans CNCTC 8/77, Staphylococcus aureus ATCC 25923 Gram (+), Candida albicans ATCC 10239 (yeast) by the well diffusion method. Anti-quorum sensing activity, violacein inhibition activity, and anti-swarming activity were studied using Chromobacterium violaceum CV026 and C. violaceum ATCC 112472, and Pseudomonas aeruginosa (PA01) respectively. Both propolis extracts were detected antibacterial activity against Gram (+) bacteria and Candida albicans. However, antibacterial activity against Gram (-) bacteria were not observed. While the antimicrobial activity of water extract propolis was determined more effectively than ethanol extract, anti-quorum sensing and anti-swarming activities less effective. It was also detected that both extracts display violacein inhibition. It was revealed that the antimicrobial, anti-quorum sensing, anti-swarming activity depended on the dose of propolis extracts. Thirty-six phenolic compounds were analysed of propolis extract by HPLC-DAD. The amount and presence of phenolic compounds in the ethanol extract were more than the water extract apart from benzoic acid, cinnamic acid, syringic acid, (±) epigallocatechin, vitexin, rutin, and trans-chalcone. Consequently, the study put forward that the phenolic compounds of propolis have antibacterial, anti-quorum sensing, violacein inhibition, and anti-swarming activities changing depend on directly the extraction solvent and phenolic compounds. Çoğunluğu algılama sistemi bakterilerin sinyal molekülleri ile kendi aralarında iletişim kurmasını sağlayan özel bir sistemdir. Propolis bal arılarının bitkilerden topladığı reçinedir. Bu çalışmada etanol ve su ekstrakt propolisin antimikrobiyal ve antiçoğunluk algılama aktivitesi incelendi. Propolis ekstraktlarının antimikrobiyal aktivitesi Escherichia coli ATCC 25922, Listeria monocytogenes ATCC 7644, Streptococcus mutans CNCTC 8/77, Staphylococcus aureus ATCC 25923 ve Candida albicans ATCC 102392’e karşı disk difüzyon yöntemi ile çalışıldı. Anti-çoğunluk algılama, violacein inhibisyon ve kaynaşma önleyici aktiviteleri sırasıyla Chromobacterium violaceum CV026, C. violaceum ATCC 112472 ve Pseudomonas aeruginosa PA01 ile çalışıldı. Propolis ekstraktlarının Gram (+) bakteriler ve Candida albicans üzerine antimikrobiyal etkisi olmasına rağmen Gram (-) bakterilerde herhangi bir etki tespit edilememiştir. Sulu ektrakt propolisin antibakteriyel aktivitesi etanol ekstrakt propolise göre daha yüksek iken antiçoğunluk algılama ve kaynaşma önleyici aktivitesi daha az olduğu tespit edildi. Violacein inhibisyon aktivitesi ise her iki propolis ekstraktında da tespit edildi. Propolis ekstraktlarının antibakteriyel, anti-çoğunluk algılama ve kaynaşma önleyici aktiviteleri doza bağımlı olarak değiştiği görüldü. Propolis ekstraktlarında otuz altı fenolik bileşik HPLC-DAD ile analiz edildi. Benzoik asit, sinnamik asit, şiringik asit, epigallokateşin, viteksin rutin ve kalkon dışındaki tüm fenolik bileşikler hem miktarı hem de yaygınlığı etanol ekstrakt propoliste daha yüksek olduğu belirlendi. Sonuç olarak bu çalışma propolisin ekstraksiyon solventine ve içeriğindeki fenolik bileşiklere bağlı olarak antimikrobiyal, anti-çoğunluk algılama, violacein inhibisyon ve kaynaşma önleyici aktivitelerinin olduğunu ortaya koydu.

0000-0002-1865-1093; WOS: 000554351800001 PubMed ID: 32701174 In this study, a novel pH-sensitive hydrogel beads that is based on gelatin/sodium alginate/chitosan (GEL/SA/CS) loaded with propolis ethanolic extracts (PE) were synthesized. The swelling behavior of GEL/SA/CS hydrogel beads was studied in different pH solutions and compared with unloaded CS (GEL/SA) hydrogel beads. Thein vitrorelease studies have been revealed using four different pH (1.3, 5.0, 6.0, and 6.8), a saliva environment (pH 6.8), a simulated gastric fluid (SGF) (pH 1.3), and a simulated intestinal fluid (SIF) (pH 6.8) to simulate the physiological conditions in gastrointestinal (GI) tract. Propolis-loaded hydrogel beads were found to be stable at pH 1.3, 5.0, 6.0, simulated saliva, SGF, and SIF mediums, whereas the beads lose their stability at pH 6.8 buffer solution. Tested microorganisms displayed greater sensitivity to PE-loaded hydrogel beads compared with pure propolis. Contrary to antimicrobial activity results, antibiofilm activity results of PE-loaded GEL/SA and GEL/SA/CS hydrogel beads were found at low levels. According to the obtained results, the propolis-loaded GEL/SA/CS hydrogel beads synthesized within this study can be used in the treatment of GI tract diseases such as oral mucositis, gastric ulcer, ulcerative colitis, and GI cancer, as controlled releasing carriers of propolis. Scientific Research Projects Office of Mugla Sitki Kocman UniversityMugla Sitki Kocman University [BAP 2013/139] This study is a part of a MSc thesis and supported by Scientific Research Projects Office of Mugla Sitki Kocman University under BAP 2013/139 project number.