Abstract The qualitative and quantitative chemical composition (total phenolics, tannins and flavonoids contents), as well as the antioxidant activity of an ethanolic extract of the leaves of Coccoloba cowellii (Polygonaceae) was determined in this study. The extract was prepared by dynamic ultrasound-assisted extraction using firstly petroleum ether:ethyl ether (1:1, v/v) and therefore ethanol:water (8:2, v/v). Quantitative chemical composition (total phenolics, tannins and flavonoids content) was determined using spectroscopic techniques, while the antioxidant activity was determined by means of the 1,1-diphenyl-2-picryl-hydrazyl (DPPH) and ferric reducing power tests. The ethanolic extract showed significant antioxidant activity in both assays, with values of 34,01 % ± 4,03 % in the DPPH and reduced Fe3+ ferricyanide complex to the ferrous form (Fe2+), similar to the ascorbic acid used as standard in both assays. The antioxidant activity of the extract is consistent with the total phenolic, tannins and flavonoid contents of the extract.

Resumen En este trabajo se determinó la composición química cualitativa y cuantitativa (contenido de compuestos fenólicos, taninos y flavonoides totales), así como la actividad antioxidante in vitro de un extracto etanólico de las hojas de Coccoloba cowelli (Polygonaceae). Para ello se realizó una extracción dinámica asistida por ultrasonido con éter de petróleo:éter etílico (1:1, v/v) y luego con etanol:agua (8:2, v/v). En los extractos se cuantificaron los compuestos fenólicos, taninos y flavonoides totales mediante técnicas espectrofotométricas. La actividad antioxidante fue determinada mediante los ensayos del radical 1,1-difenil-2-picrilhidracil (DPPH) y del poder reductor. El extracto etanólico mostró actividad antioxidante significativa en ambos ensayos, con valores de 34,01 % ± 4,03 % en el DPPH y reduciendo el complejo Fe3+ ferricianuro a su forma ferrosa, los que fueron comparables al del ácido ascórbico usado como estándar. La actividad antioxidante es consistente con el contenido de compuestos fenólicos, taninos y flavonoides totales del extracto.

Propolis is a resinous mixture of different plant exudates collected by honeybees. Currently, propolis is widely used as a food supplement and in folk medicine. We have evaluated 20 Cuban propolis extracts of different chemical types, brown (BCP), red and yellow (YCP), with respect to their in vitro antibacterial, antifungal and antiprotozoal properties. The extracts inhibited the growth of Staphylococcus aureus and Trichophyton rubrum at low µg/mL concentrations, whereas they were not active against Escherichia coli and Candida albicans. The major activity of the extracts was found against the protozoa Leishmania, Trypanosoma and Plasmodium, although cytotoxicity against MRC-5 cells was also observed. The BCP-3, YCP-39 and YCP-60 extracts showed the highest activity against P. falciparum, with 50% of microbial growth (IC50) values of 0.2 µg/mL. A positive correlation between the biological activity and the chemical composition was observed for YCP extracts. The most promising antimicrobial activity corresponds to YCP subtype B, which contains acetyl triterpenes as the main constituents. The present in vitro study highlights the potential of propolis against protozoa, but further research is needed to increase selectivity towards the parasite. The observed chemical composition-activity relationship of propolis can contribute to the identification of the active principles and standardisation of this bee product.

In the present study, an extensive in vitro antimicrobial profiling was performed for three medicinal plants grown in Cuba, namely Simarouba glauca, Melaleuca leucadendron and Artemisia absinthium. Ethanol extracts were tested for their antiprotozoal potential against Trypanosoma b. brucei, Trypanosoma cruzi, Leishmania infantum and Plasmodium falciparum. Antifungal activities were evaluated against Microsporum canis and Candida albicans whereas Escherichia coli and Staphylococcus aureus were used as test organisms for antibacterial activity. Cytotoxicity was assessed against human MRC-5 cells. Only M. leucadendron extract showed selective activity against microorganisms tested. Although S. glauca exhibited strong activity against all protozoa, it must be considered non-specific. The value of integrated evaluation of extracts with particular reference to selectivity is discussed.