Antimicrobial effect of 4-hydroxybenzoic acid ester with glycerol.

WHAT IS KNOWN AND OBJECTIVES: Parabens have been commonly used as preservatives in pharmaceutical and cosmetics industries for almost 50 years. These compounds are thermostable, pH-stable and inexpensive and have a wide antimicrobial effect. The antimicrobial activity of parabens in emulsion system is limited by their poor solubility in water phase, which is increasing with the length of their alkyl chain. The aim of this work was preparation of 1-O-(4-hydroxybenzoyl)-glycerol, more hydrophilic and naturally occurring analogue of parabens, and comparison of its antimicrobial activity with commercially used parabens (4-hydroxybenzoic acid, methylparaben, ethylparaben, propylparaben). METHODS: 1-O-(4-Hydroxybenzoyl)-glycerol was obtained by the transesterification reaction of methyl paraben with glycerol. Purity was confirmed by determination of melting point and by GC/MSD. Antimicrobial activity of 1-O-(4-hydroxybenzoyl)-glycerol and commercially used parabens was determined by spectrophotometrical monitoring of microbial growth in media containing the testing substances, using spectrophotometers PowerWave XS and Cary 50 Conc. RESULTS AND DISCUSSION: 1-O-(4-Hydroxybenzoyl)-glycerol was prepared with purity >99%. This compound showed antimicrobial activity against all tested microorganisms (Staphylococcus aureus, Escherichia coli, Saccharomyces cerevisiae and Fusarium culmorum). In comparison with other tested substances, 1-O-(4-hydroxybenzoyl)-glycerol showed less inhibitory activity at the highest concentration of 20 mmol/L, with the maximum inhibitory activity ca. 70%. On the other hand, antimicrobial activity of 1-O-(4-hydroxybenzoyl)-glycerol at the lower concentrations (2·5 mmol/L, 1·25 mmol/L) was the same or, in some cases, even higher (S. aureus) in comparison with commercially used parabens. WHAT IS NEW AND CONCLUSION: A novel hydrophilic analogue of parabens was synthetized and tested for its antimicrobial activity against selected microorganisms in model system. This study confirms antimicrobial potential of 1-O-(4-hydroxybenzoyl)-glycerol, which is comparable with other commercially used parabens. Unlike commercial parabens, it is possible to expect more significant antimicrobial activity of 1-O-(4-hydroxybenzoyl)-glycerol in real emulsion systems due to the increased solubility of this substance in water phase and also the lower skin irritation.

The microhabitat distribution of two Dactylogyrus species parasitizing the gills of the barbel, Barbus barbus.

The microhabitat distribution of two congeneric species Dactylogyrus carpathicus and D. malleus (Monogenea) parasitizing the gills of the barbel (Barbus barbus L.) was investigated. We tested whether congeneric species exhibited microhabitat preference and whether interspecific interactions could be attributed to the microhabitat segregation of congeners. The outlying mean index method was used to evaluate species microhabitats. Gill variables (different microhabitats within gills) were used as environmental factors characterizing the gills. When abundances of both species were highest, and no significant difference was found between the abundance of the two species, the gill segments and gill areas were the most important factors segregating the Dactylogyrus species on the gills. Niche overlap was low within each of the four gill arches, and parasites were segregated in the same microhabitats within each gill arch. When abundances of both species were low, each monogenean species was segregated at the level of the gill arches. When abundances of both species increased, the niche and overlap between species increased. The distribution of both congeneric species confirmed microhabitat preference within the gills. The results suggest that microhabitat preference is dependent on species abundances, species being segregated in the case of low abundance, possibly to increasing mating opportunities. Both niche and overlap between species increased with species abundance. In the case of the high abundance of both species, microhabitat preference seems to be related to interspecific interactions between monogenean species, as previously found for endoparasitic species.

Water temperature influencing dactylogyrid species communities in roach, Rutilus rutilus, in the Czech Republic.

Dactylogyrid species (Monogenea) communities were studied in roach, Rutilus rutilus, collected from two localities in the basin of Morava river, Czech Republic, during the period from April to November 1997 and March to September 1998 to determine the effect of water temperature on parasite abundance, species richness and diversity. Dactylogyrid species were found to co-occur on the gills of roach with up to six species found on the same host individual. Nine dactylogyrid species were identified with the abundance of each reaching a very low level. Niche size was considered to increase with species abundance even when water temperature was high. There was a strong effect of water temperature on abundance of the common dactylogyrid species (D. crucifer, D. nanus, D. rutili and D. suecicus) as well as of the rare species D. rarissimus. The temporary occurrence of the rare species was found without any temperature effect. Water temperature did not affect the relationship between abundance and niche size. Niche size increased with abundance, even when the water temperature was high, which suggests that negative interspecific interactions are not important within dactylogyrid communities.