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DOI: 10.1055/s-2006-949877
Essential oil of Turkish Origanum onites L. and its main components, carvacrol and thymol show potent antiprotozoal activity without cytotoxicity
Origanum species (Lamiaceae) are natural floristic elements of Turkey and widely used as traditional medicines and flavor enhancers in foods [1]. Oregano herb is also an important commercial product of Turkey, where Origanum onites accounts for 80% of all the oregano exports of the country. The plant is characterized by high yield of essential oil that contains very high amounts (up to 80%) of carvacrol as major constituent [2]. In the continuation of our search for new antiparasitic agents from Turkish plants [3], we have investigated the in vitro activity of the essential oil of Origanum onites L. against several parasitic protozoa, namely Trypanosoma brucei rhodesiense, Leishmania donovani and Plasmodium falciparum. The essential oil was obtained via hydrodistillation from the dried herbal parts of Origanum onites and the analyses were performed on a GC and GC-MS system simultaneously. Carvacrol (70%), linalool (9.7%), p-cymene (7%), gamma-terpinene (2%), and thymol (1.7%) were identified as main components. The oil showed very significant activity against T. b. rhodesiense (IC50 186 ng/mL), and moderate antileishmanial and antiplasmodial effects (IC50 values 17.8 and 7.9µg/mL, respectively). As a next step, the main constituent, carvacrol, but also its position isomer, thymol, were tested. Interestingly, both compounds have retained the same activities as observed for the oil. Furthermore, their trypanocidal activity was even stronger (IC50 value for thymol: 114 ng/mL, for carvacrol: 149 ng/mL). Since both the oil and its two components are devoid of cytotoxicity on mammalian L6 cells (IC50s >50µg/mL), they are currently being evaluated on animal models for in vivo trypanocidal activity.
References: 1. Baser, K.H.C. (2002), Oregano. Taylor & Francis. London. 2. Demirci, F. et al. (2004), J. Agric. Food. Chem. 52: 251–254. 3. Tasdemir, D. et al. (2005), Phytochemistry 66: 355–362.