Variation of the analgesic effect of carvacrol: Influence of solvents.

A Cakmak, S Aydin. Anadolu University Faculty of Pharmacy, Department of Pharmacology 26470, Turkey

Carvacrol is an oxygenated cyclic monoterpene widely found in nature and also obtained synthetically. In various plant extracts and essential oils it is found as major compound and thus reported to have various pharmacological actions including analgesia (Guimaraes et al, 2010). There are different and conflicting reports on the pharmacological activities of carvacrol including analgesic actions.

The aim of this study was to investigate the analgesic actions of carvacrol in different solvent media like dimethyl sulfoxide (DMSO) and sunflower oil.

Carvacrol (100 mg.kg-1 i.p.) solved in DMSO and sunflower oil applied to the either sex of Balb/c mice (28-32 g) and tail-clip and tail-immersion (52.5oC) tests were used for analgesic activities. Tests were conducted 30 min after the application of test compounds and cut-off time was 15 seconds. Morphine sulphate (10 mg.kg-1 , s.c.) was used for standard analgesic drug. Three groups of mice (n = 7, per group) were organized as; (I) Carvacrol dissolved in DMSO treated group; (II) Carvacrol dissolved in sunflower oil treated group and (III) Morphine treated group.

Percent analgesia values of the data were calculated using the formula given below and statistically evaluated using one way variance analysis followed by Tukey HSD test for multiple comparison test . p < 0.05 was considered as statistically significant.

%analgesia={(postdrug latency)-(predrug latency)/(cutoff time)-(predrug latency)} x 100

As a result carvacrol dissolved in the sunflower oil and DMSO alone were inactive whereas carvacrol dissolved in DMSO exhibited analgesic action. Our results demonstrated that the media used to dissolve carvacrol have important roles on the pharmacological actions and more importantly the previous tests which test substances were dissolved in sunflower oil must be re-evaluated and conducted again. The important role of DMSO when used as vehicle for test substances in the observed analgesic actions must be examined also for other test compounds other than monoterpene groups as well.

Guimaraes AG, Oliveira GF, Melo MS, Cavalcanti SCH, Antoniolli AR, Bonjardim LR et al (2010).Bioassay-guided evaluation of antioxidant and antinociceptive activities of carvacrol. Basic Clin Pharmacol Toxicol 107: 949-957.