Milena Popova

Chemical Composition of European Propolis: Expected and Unexpected Results

Ten propolis samples from Bulgaria, Italy and Switzerland were analyzed by GC-MS. As expected, most samples displayed the typical chemical pattern of “poplar” propolis: they contained pinocembrin, pinobanksin and its 3-O-acetate, chrysin, galangin, prenyl esters of caffeic and ferulic acids. Two samples differed significantly: one from the Graubünden Alpine region, Switzerland, rich in phenolic glycerides, and one from Sicily which contained only a limited number of phenolics and was rich in diterpenic acids.

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).

Terpenes with antimicrobial activity from Cretan propolis.

Five terpenes, the diterpenes: 14,15-dinor-13-oxo-8(17)-labden-19-oic acid and a mixture of labda-8(17),13E-dien-19-carboxy-15-yl oleate and palmitate as well as the triterpenes, 3,4-seco-cycloart-12-hydroxy-4(28),24-dien-3-oic acid and cycloart-3,7-dihydroxy-24-en-28-oic acid were isolated from Cretan propolis. Moreover, 18 known compounds were also isolated, seven of them for the first time as propolis components. All structures were established on the basis of spectroscopic analysis and chemical evidence. All isolated compounds were tested for antimicrobial activity against some Gram-positive and Gram-negative bacteria as well as against some human pathogenic fungi showing a broad spectrum of antimicrobial activity.

Chemical composition of propolis from Canada, its antiradical activity and plant origin.

The chemical composition of propolis from two regions in Canada was studied: Boreal forest and the Pacific coastal forest that lie outside the area of distribution of Aigeiros poplars, the usual propolis source plants. In the sample from Victoria, p-hydroxyacetophenone, benzyl hydroxybenzoate and cinnamic acid were the major components, accompanied by significant amounts of dihydrochalcones, which allowed the identification of its plant source: Populus trichocarpa of section Tacamahaca. Three dihydrochalcones were new for propolis. The sample from Richmond was characterized by large amounts of p-coumaric and cinnamic acid, typical for poplars of section Leuce, subsection Trepidae, its plant source was identified as P. tremuloides. Both samples showed a good radical scavenging activity against DPPH. Obviously, the Northern type propolis is a promising potential source of biologically active substances and deserves further investigation.

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 volatile compounds: chemical diversity and biological activity: a review

Propolis is a sticky material collected by bees from plants, and used in the hive as building material and defensive substance. It has been popular as a remedy in Europe since ancient times. Nowadays, propolis use in over-the-counter preparations, “bio”-cosmetics and functional foods, etc., increases. Volatile compounds are found in low concentrations in propolis, but their aroma and significant biological activity make them important for propolis characterisation. Propolis is a plant-derived product: its chemical composition depends on the local flora at the site of collection, thus it offers a significant chemical diversity. The role of propolis volatiles in identification of its plant origin is discussed. The available data about chemical composition of propolis volatiles from different geographic regions are reviewed, demonstrating significant chemical variability. The contribution of volatiles and their constituents to the biological activities of propolis is considered. Future perspectives in research on propolis volatiles are outlined, especially in studying activities other than antimicrobial.

GC-MS Profiling of Diterpene Compounds in Mediterranean Propolis from Greece

The objective of this work is to analyze and identify the diterpene compounds in Mediterranean propolis samples from different Greek regions by GC-MS. The chemical composition of six propolis samples was established using previously isolated diterpenes from Cretan propolis as authentic standards for identification, based on mass spectral fragmentation of the TMS derivatives and retention index. More than 30 diterpenes, among which were new propolis constituents, were identified and characterized by means of authentic standards and interpretation of MS fragmentation as well. This is the first detailed profiling of a new type of propolis, rich in diterpenes. The chromatographic and mass- spectral characteristics of the diterpenes identified could be very useful for rapid GC-MS profiling of this propolis type and for revealing its plant sources.

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.

Beneficial effects of probiotics in upper respiratory tract infections and their mechanical actions to antagonize pathogens

Probiotics are live micro‐organisms with beneficial effects on human health, which have the ability to counteract infections at different locations of the body. Clinical trials have shown that probiotics can be used as preventive and therapeutic agents in upper respiratory tract infections (URTIs) and otitis. Their mechanical properties allow them to aggregate and to compete with pathogens for nutrients, space and attachment to host cells. Consequently, they can directly antagonize pathogens and thus exert beneficial effects without directly affecting the metabolism of the host. An overview of the probiotics with such traits, tested up to date in clinical trials for the prevention or treatment of URTIs and otitis, is presented in this review. Their mechanical properties in the respiratory tract as well as at other locations are also cited. Species with interesting in vitro properties towards pharyngeal cells or against common respiratory pathogens have also been included. The potential safety risks of the cited species are then discussed. This review could be of help in the screening of probiotic strains with specific mechanical properties susceptible to have positive effects in clinical trials against URTIs.

Coumarins from Angelica lucida L. - Antibacterial Activities

The first phytochemical investigation of the fruits of Angelica lucida has led to the isolation and characterization of five known coumarins (imperatorin, isoimperatorin, heraclenol, oxypeucedanin hydrate and heraclenin). All isolated compounds were identified by means of spectral and literature data. The extracts and the isolated constituents from A. lucida have been also evaluated for their antimicrobial activity against six Gram positive and negative bacteria, two oral pathogens and three human pathogenic fungi, exhibiting an interesting antimicrobial profile.