Background and Aim: Thymol and carvacrol are two important components of thyme that
have multiple medicinal uses. This study investigates the in vivo effects of these
natural products on adjuvant-induced inflammation and secretion of interleukin (IL)-17
and key inflammatory cytokines in rats.
Materials and Methods: We injected complete Freund’s adjuvant (CFA) into the hind
paws of rats in order to induce inflammation. Each of the CFA-treated rat groups received
gavages of thymol, carvacrol, or vehicle (CFA-only group). Rats’ paws and ankle edema
were measured and then we were able to determine an inflammatory score based on the
results. After 72 h of inflammation induction, sera were collected and subsequently
inflamed tissue extracts were prepared for cytokine assay by ELISA.
Results: Both components significantly decreased paw edema in rats (p<0.01). Thymol
decreased ankle edema to 61.6% of edema in CFA-only rats (p<0.001). We observed a
decreased inflammatory score in the thymol and carvacrol-treated rats. The evaluation
of the tissue and serum inflammatory cytokine levels showed that both components decreased
tumor necrosis factor (TNF)-α levels (p<0.05). Thymol and carvacrol reduced interleukin
(IL)-1β serum and tissue levels, respectively. These components reduced tissue levels
of IL-17 from 148.4±13.4pg/ml in CFA-only rats to 90.1±18.9pg/ml (thymol) and 82.3±9.2pg/ml
(carvacrol). Both components decreased serum IL-17 levels in rats (p<0.05). In comparison,
the anti-inflammatory drug, indomethacin, reduced the inflammatory score and decreased
tissue TNF-α and IL-1β levels but did not affect IL-17 production.
Conclusion: Carvacrol and thymol could relieve inflammation symptoms possibly by downregulating
serum and tissue IL-17 expression in addition to key pro-inflammatory cytokines, TNFα