In vitro evaluation of surfactants with eucalyptus oil for respiratory distress syndrome

The effects of low doses of eucalyptus oil (EO) were studied on the surface properties of phospholipid suspensions as exogenous surfactants, by in vitro analysis using a pulsating bubble surfactometer and a Wilhelmy balance. Survanta, ALEC and Exosurf, commonly used surfactants in therapy of respiratory distress syndrome were used as controls for comparison. The test surfactants, in Ringer's lactate at 1%, were pulsated at 40 cpm in the surfactometer. EO caused a significant improvement of adsorption of the surfactants. In the case of the binary mixture of dipalmitoylphosphatidylcholine and phosphatidylethanolamine (2:3), EO significantly improved the adsorption, stability and minimum surface tension obtained. This combination performed better than ALEC and Exosurf and was comparable to Survanta with respect to minimum surface tension attained. The re-spreading of a surface excess film of this mixture in a Wilhelmy balance was higher than that of ALEC and Exosurf. The ultrastructure of the EO enriched surfactants using cryogenic scanning electron microscopy showed easy facturability and formation of open membranous structures, which could have been associated with the improved surface activity.