In vitro antibacterial and antifungal activity of a skin ointment and its active pharmaceutical ingredients larch turpentine, turpentine oil, and eucalyptus oil.

Introduction: Turpentine derivatives and Eucalyptus oil are herbal substances traditionally used to treat various skin infections. Limited non-clinical data suggest they exert an immunological activity, but only scant information exists on their antibiotic effects. This in vitro study has been carried out to investigate the antibacterial and antifungal activity of a marketed skin ointment, its active pharmaceutical ingredients larch turpentine, eucalyptus oil, and turpentine oil, and their mixture, against bacteria and yeasts commonly present on the skin and causing skin infections.

Methods: The antibiotic activity was tested using the drop dilution assay on the Gram-positive bacteria Staphylococcus aureus (wild type), a methicillin resistant S. aureus strain, S. epidermidis, S. haemolyticus, Streptococcus pyogenes, the Gram-negative Pseudomonas aeruginosa, and the yeasts Candida albicans and C. tropicalis.

Results: The ointment exerts a strong inhibitory effect on all Gram-positive bacteria at a concentration of 5 g/100 mL in the Müller-Hinton medium. It also has inhibiting effect on both Candida species but does not inhibit P. aeruginosa growth. As for the single active pharmaceutical ingredients, larch turpentine was the most active substance. The mixture of the three ingredients, in the concentrations used in the ointment, had a higher antibiotic effect than any of the individual ingredients studied, suggesting at least an additive activity.

Conclusions: Our study has shown that the herbal ingredients and their combination exert antimicrobial activities, especially against Gram-positive bacteria, that justify their use in the treatment of skin infections.