Effect of Myrtol Standardized and Other Substances on the Respiratory Tract: Ciliary Beat Frequency and Mucociliary Clearance as Parameters

Abstract

Myrtol standardized is a phytomedicine obtained by distillation, consisting of many constituents. In vitro and in vivo, the major monterpenes, d-limonene, 1,8-cineole, and alpha-pinene, are used as biological marker substances. Myrtol standardized has secretolytic, secretomotor, and mucolytic effects in addition to anti-inflammatory and antioxidative actions. The aim of the study was to investigate the effects of different concentrations of Myrtol standardized on in vivo mucociliary clearance in mice and the ciliary beat frequency (CBF) in rat tracheal rings. Data regarding the effects of 1,8-cineole and N-acetylcysteine (NAC) were compared. Salbutamol was used as a positive control. CBF was measured using rat tracheal explants and a high-speed video camera linked to a microscope with specific software equipment. Mucociliary clearance was determined using the microdialysis technique, which measured the acceleration of a fluorescent sample in the trachea in vivo. Myrtol standardized accelerated both CBF and mucociliary transport in a concentration-dependent manner. Significant effects were seen at a concentration of 0.01% Myrtol regarding CBF (P<0.01) and 17.1 mg/kg body weight regarding mucociliary clearance experiments (P<0.05) according to doses relevant to humans. The 1,8-cineole dosage relative to humans only accelerated the mucociliary clearance in vivo without having an effect on the CBF. Extremely high doses of Myrtol were not able to additionally increase the CBF effect in comparison to salbutamol. Compared to NAC, also used in a dosage relative to humans, Myrtol standardized showed a tendency to be more effective. In summary, the present data suggest that Myrtol standardized is a pharmacologically important drug which, when used at a dose relative to humans, shows positive effects on both measured parameters, CBF and mucociliary clearance, in vivo.