Methyl paraben as a sex pheromone in canine urine--is the question still open?

The literature concerning the issue of canine sex pheromones includes reports presenting completely conflicting opinions about the chemical composition of the canine urine in the context of semiochemical communication. At present, the predominant report cited by many different authors is the article published in Science in 1979 by Goodwin at al., presenting methyl p-hydroxybenzoate (methyl paraben) as the main canine sex pheromone. While it has been proved that pure methyl paraben lacks semiochemical activity as do commercially available products containing this substance (Eau D'Estrus, Synbiotics, USA), in view of the conflicting published reports the aim of this study was to revaluate using modern techniques the presence of methyl p-hydroxybenzoate in canine urine during different phases of the ovarian cycle. Ten female dogs of different breeds were used. Urine samples from bitches collected during various stages of the ovarian cycle were examined with using the SPME and GC/MS methods. Methyl paraben was not detected in any of the samples. In conclusion, because of the lack of methyl-p-hydroxybenzoate in the samples examined, the present study confirmed negative opinions on the possibility of this substance playing a crucial role in semiochemical communication during reproduction in dogs (Canis familiaris).