The antimicrobial properties of volatile aromatic
oils from medicinal as well as other edible plants has been recognized since antiquity.
Origanum oil, which is used as a food
flavoring agent, possesses a broad spectrum of in vitro antimicrobial activities attributed to the high content of phenolic derivatives such as
carvacrol and
thymol. In the present study, antifungal properties of
origanum oil were examined both in vitro and in vivo. Using Candida albicans in broth cultures and a micro dilution method, comparative efficacy of
origanum oil,
carvacrol,
nystatin and
amphotericin B were examined in vitro.
Origanum oil at 0.25 mg/ml was found to completely inhibit the growth of C. albicans in culture. Growth inhibitions of 75% and >50% were observed at 0.125 mg/ml and 0.0625 mg/ml level, respectively. In addition, both the germination and the mycelial growth of C. albicans were found to be inhibited by
origanum oil and
carvacrol in a dose-dependent manner. Furthermore, the therapeutic efficacy of
origanum oil was examined in an experimental murine
systemic candidiasis model. Groups of mice (n = 6) infected with C. albicans (5 x LD50) were fed varying amounts of
origanum oil in a final vol. of 0.1 ml of
olive oil (vehicle). The daily administration of 8.6 mg of
origanum oil in 100 microl of
olive oil/kg
body weight for 30 days resulted in 80% survivability, with no renal burden of C. albicans as opposed to the group of mice fed
olive oil alone, who died within 10 days. Similar results were obtained with
carvacrol. However, mice fed
origanum oil exhibited cosmetically better clinical appearance compared to those cured with
carvacrol. The results from our study encourage examination of the efficacy of
origanum oil in other forms of systemic and superficial
fungal infections and exploration of its broad spectrum effect against other pathogenic manifestations including
malignancy.