Comparative study of in vitro methods used to analyse the activity of propolis extracts with different compositions against species of Candida

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.

Four compounds were isolated from Brazilian propolis. They are identified as: (1) 3-prenyl-4-hydroxycinnamic acid (PHCA), (2) 2,2-dimethyl-6-carboxyethenyl-2H-1-benzopyrane (DCBEN), (3) 3,5-diprenyl-4-hydroxycinnamic acid (DHCA), and (4) 2,2-dimethyl-6-carboxyethenyl-8-prenyl-2H-1-benzopyran (DPB). The structures of the compounds were determined by MS and NMR techniques. All compounds were assayed against Trypanosoma cruzi and the bacteria Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus and Streptococcus faecalis. Compounds (1) to (4) were active against T. cruzi. Except (1), all compounds presented activity against the bacteria tested. When compounds (1)-(3) were tested in the guinea pig isolated trachea, all induced a relaxant effect similar to propolis extract.

Propolis is extensively used in Argentine folk medicine. Alcoholic extracts of propolis from different regions of Argentina were prepared. The extracts were analysed for the determination of total flavonoid content (from 13.3 to 42.6 mg/g of propolis) by using the aluminum nitrate method, UV spectrophotometry and thin layer chromatography. All of them contained high total flavonoid content. It was also observed that all samples of ethanolic extracts of propolis showed free radical-scavenging activity in terms of scavenging of the radical DPPH but the highest activities were found for samples from Tucumán and Santiago del Estero. In all cases with 20 microg/ml of soluble principles, the percentage of DPPH degradation was different (Banda Oeste: 67.5%; Verónica: 45%; Forres: 35%; Saenz Peña: 20% and Juan José Castelli: 55%). These results may justify their use as a source of natural antioxidants.