Iva Tsvetkova

Antibacterial, antifungal and antiviral activity of propolis of different geographic origin

Propolis samples from different geographic origins were investigated for their antibacterial (against Staphylococcus aureus and Escherichia coli), antifungal (against Candida albicans) and antiviral (against Avian influenza virus) activities. All samples were active against the fungal and Gram-positive bacterial test strains, and most showed antiviral activity. The activities of all samples were similar in spite of the differences in their chemical composition. In samples from the temperate zone, flavonoids and esters of phenolic acids are known to be responsible for the above mentioned activities of bee glue; tropical samples did not contain such substances but showed similar activities. Obviously, in different samples, different substance combinations are essential for the biological activity of the bee glue. It seems that propolis has general pharmacological value as a natural mixture and not as a source of new powerful antimicrobial, antifungal and antiviral compounds.

Bioactive Constituents of Brazilian Red Propolis

In a new propolis type, red Brazilian propolis, 14 compounds were identified (six of them new for propolis), among them simple phenolics, triterepenoids, isoflavonoids, prenylated benzophenones and a naphthoquinone epoxide (isolated for the first time from a natural source). Three of the major components demonstrated significant antimicrobial activity, and two (obtained as inseparable mixture) possessed radical scavenging activity against 1,1-diphenyl-2-picrylhydrazyl (DPPH).

Antibacterial ent-kaurene from Brazilian propolis of native stingless bees.

Three ent-kaurene diterpenoids, not previously described as constituents of propolis, were isolated from a sample collected by Brazilian native bees Melipona quadrifasciata anthidioides. One of them, kaurenoic acid, as well as the total extract, displayed moderate antibacterial activity.

Chemical characteristics of poplar type propolis of different geographic origin

Validated spectrophotometric procedures were used to quantify three main groups of bioactive substances (phenolics, flavones/flavonols, flavanones/dihydroflavonols) in 114 samples of poplar-type propolis from different geographic origins. From the results, we characterized raw poplar propolis in terms of minimum content of its bioactive components (antimicrobial and antioxidant) as follows: 45% resin, 21 % total phenolics, 4% total flavones/flavonols; 4% total flavanones/dihydroflavonols, and a maximum Minimum Inhibitory Concentration (MIC) against S. aureus of 250 μg/mL. A significant negative correlation was observed between the amount of total phenolics and MIC. The results indicate that measuring the concentrations of groups of active compounds, rather than individual components, is an appropriate approach in developing quality standards for propolis.ZusammenfassungZiel dieser Arbeit ist, die typischen Eigenschaften von Pappel-Rohpropolis bezüglich des Gehalts an bioaktiven Komponenten (antimikrobiell und antioxidant) zu bestimmen. Hierzu wurden validierte spektrophotometrische Verfahren für die Quantifizierung der drei Hauptgruppen bioaktiver Substanzen (Phenole, Flavone/Flavonole, Flavanole/Dihydroflavonole) an 114 Proben unterschiedlicher geografischer Herkunft durchgeführt. Weiter wurde die Menge von Balsam (Extrakt mit 70 % Ethanol) und die minimale Hemmkonzentration (MIC) gegen Streptococcus aureus gemessen. Die Messwerte für diese Charakterisierungen sind in Tabelle I. aufgeführt. Obwohl die chemische Zusammensetzung von Pappelknospenexudaten verhältnismäßig konstant ist, könnte es signifikante Abweichungen in dem Prozentsatz der einzelnen Komponenten an unterschiedlichen Orten geben (Abb. 1). Die Messwerte waren nicht normal verteilt, daher empfehlen wir die empirischen 20 % Quantile zur Festsetzung des minimalen Balsamgehaltes und des Gehaltes an biologisch aktiven Komponenten, sowie des 80 % Quantils für MIC. Hieraus ergibt sich für die Minimalgehalte im Einzelnen: Balsam 45 %, Phenole insgesamt 21 % (im Rohpropolis), Flavone und Flavonole 4 % (im Rohpropolis), Flavanone und Dihydroflavonole 4 % (im Rohpropolis), und für MIC gegenüber Staphylococcus aureus ein Maximum von 250 μg/mL (im Trockenbalsam). Durch eine ANOVA konnte gezeigt werden, dass große Höhen sowie nördliche Breiten einen Einfluss auf den Gehalt an biologisch aktiven Substanzen haben, die Konzentrationen sind hier etwas niedriger. Allerdings ist dieser Einfluss von geringer Bedeutung, da er die biologische Aktivität der Proben nicht signifikant beeinflusste. Eine weitere wichtige Beobachtung war ein negativer Zusammenhang zwischen der Konzentration der Gesamtphenole im Propolisbalsam und MIC (P = 0,003). Bisher war ein solcher Zusammenhang nicht statistisch belegt. Die Ergebnisse sind für die Standardisierung von Propolis von besonderem Interesse. Sie unterstützen unser Konzept einer Vörgehensweise der Erfassung ganzer Gruppen bioaktiver Substanzen anstelle von Einzelkomponenten. Unsere Ergebnisse deuten weiter darauf hin, dass die Messung von MIC auf Grund der komplexen synergistischen Effekte der verschiedenen Propoliskonstituenten ein obligatorisches Element der Qualitätskontrolle sein sollte. Weiter ist wichtig daran zu erinnern, dass verschieden Propolistypen unterschiedliche chemische Zusammensetzung haben und die gezogenen Schlussfolgerungen daher nur für Pappelpropolis gelten und keinesfalls auf andere Propolissorten übertragbar sind.

Propolis from the Mediterranean Region: Chemical Composition and Antimicrobial Activity

Abstract The chemical composition of propolis from Bulgaria, Turkey, Greece and Algeria was investigated by GC-MS. All of them contained mainly flavonoids and esters of caffeic and ferulic acids, which indicated that their main source are buds of poplars of the taxonomic section Aegieros. Some Turkish samples contained a low percent of diterpenic acids, while in Algerian samples significant amounts of a hydroxyditerpenic acid (M=322, its structure not determined by its MS) were found. All samples showed significant antibacterial and weak to moderate antifungal activity.

Chemical composition and biological activity of propolis from Brazilian Meliponinae.

Abstract Twenty-one propolis samples produced by 12 different Meliponinae species were analyzed by GC-MS. Several chemical types of stingless bees’ propolis could be grouped, according to the prevailing type of compounds like: “gallic acid”, “diterpenic” and “triterpenic” types. The results confirm that neither the bee species nor the geographical location determine the chemical composition of Meliponinae propolis and the choice of its plant source, respectively. This could be explained by the fact that Meliponinae forage over short distances (maximum 500 m) and thus use as propolis source the first plant exudate they encounter during their flights. The antibacterial, antifungal and cytotoxic activities of the samples were also investigated. Most samples had weak or no activity against E. coli, weak action against Candida albicans. Some of them showed significant activity against St. aureus., presumably connected to the high concentration of diterpenic acids. Samples rich in diterpenic acids possessed also high cytotoxic activity (Artemia salina test).

New biologically active compounds from Kenyan propolis.

From propolis samples from Kenya, two new arylnaphtalene lignans were isolated, tetrahydrojusticidin B 1 and 6-methoxydiphyllin 2, along with four known phenolic compounds 5-8, found for the first time in propolis. The structures of the compounds were elucidated based on their spectral properties. The geranylstilbenes 7 and 8 demonstrated antibacterial activity against S. aureus, and the geranylflavon macarangin 6 possessed antiradical activity against DPPH radicals.

Indonesian propolis: chemical composition, biological activity and botanical origin

From a biologically active extract of Indonesian propolis from East Java, 11 compounds were isolated and identified: four alk(en)ylresorcinols (obtained as an inseparable mixture) (1–4) were isolated for the first time from propolis, along with four prenylflavanones (6–9) and three cycloartane-type triterpenes (5, 10 and 11). The structures of the components were elucidated based on their spectral properties. All prenylflavanones demonstrated significant radical scavenging activity against diphenylpicrylhydrazyl radicals, and compound 6 showed significant antibacterial activity against Staphylococcus aureus. For the first time Macaranga tanarius L. and Mangifera indica L. are shown as plant sources of Indonesian propolis.

Antibacterial, antiviral, and cytotoxic activities of some red and brown seaweeds from the Black Sea.

Abstract Chloroform extracts, n- butanol extracts, water extracts,and volatile compounds from seven species belongingtosix Black Sea genera of brown algae and 10 speciesbelonging to seven Black Sea genera of red algae wereassessed for antibacterial, antiviral, and cytotoxic prop-erties. Most of the extracts showed pronounced effectsagainst the Gram (q) bacterium Staphylococcus aureus .Activity towards the Gram (-) bacterium Escherichia coli was found in only few cases. A significant reduction inreplication of influenza and Herpes simplex viruses in cellcultures was observed. Cytotoxic effect was establishedin a significant proportion of the algae investigated. Thebiological activities may be attributed to the presence ofvolatile compounds, some phenols, free fatty acids andtheir oxidized derivatives, eucalyptol, the methyl ester ofphenyl acetic acid, and 1,2-dihydroxy ethane sulfonate. Keywords: biological activities; extracts; red and brownBlack Sea algae. Introduction Marine algae have been evaluated as an attractivesourceof potential drug compounds in several biochemical andpharmacological investigations (Kerr and Kerr 1999,Luescher-Mattli 2003, Simmons et al. 2005, Lahaye andRobic 2007). Being in permanent contact with pollutants(and in order to survive in such unfriendly environments),different marine organisms, such as fungi, viruses, bac-teria, etc., synthesize or accumulate defensive com-pounds. Diverse algal extracts have been investigatedfortheir antimicrobial, cytotoxic, antitumor, antiviral, andanti-inflammatory properties (Konig and Wright 1996,Mandal et al. 2007). Our preliminary investigationsshowed that some widespread Black Sea algae possessantimicrobial, antiviral, antifungal and cytotoxic activities(Stefanov et al. 1998, Kujumdjiev et al. 1999, Serkedjieva2000, Kamenarska et al. 2002). Evidently, most of thebiologically active compounds found in marine algaehave defensive functions. A proportion of these com-pounds are secreted into surrounding seawater.In the present study, we continued the investigation ofantibacterial, cytotoxic, and antiviral activities of themostwidely distributed macroalgae in the Bulgarian part of theBlack Sea, which has not been studied until now. More-over, the results obtained were compared with the chem-ical compositions of the corresponding extracts.

Chemical Composition of the Brown Alga Padina pavonia (L.) Gaill. from the Adriatic Sea

Abstract The chemical composition of the brown alga Padina pavonia (L.) Gaill. from the southern Adriatic Sea was investigated. Twelve sterols were identified in the sterol fraction, the main ones being cholesterol and fucosterol. The main fatty acids in the lipids were also identified. The most abundant fatty acid was palmitic acid, followed by oleic and myristic acids. The concentration of polyunsaturated fatty acids was unusually low for a marine alga. By GC/MS analysis of the volatile and polar fractions, 40 compounds were identified. Some of them probably possess defensive functions. In the volatile fraction free fatty acids, aromatic esters, benzyl alcohol and benzaldehyde predominated. Low concentrations of terpenoids, phenols and sulfur containing compounds were also identified. The n-butanol extract contained mainly fatty acids and polyols. Some of the extracts had an antibacterial activity.