Antinociceptive and anti-inflammatory effects of rosmarinic acid isolated from Thunbergia laurifolia Lindl.

Rosmarinic acid (RA) was isolated from an ethanolic extract of Thunbergia laurifolia leaves. The antinociceptive activity of RA was assessed in mice using hot-plate, acetic acid-induced writhing, and formalin tests. The anti-inflammatory effects of RA were determined in two mouse models of carrageenan-induced paw edema and cotton pellet-induced granuloma formation. Orally administered RA (50, 100, and 150 mg/kg) showed significant (p<0.001) antinociceptive activity in the hot-plate test and this effect was reversed by naloxone. RA at doses of 50 and 100mg/kg significantly reduced acetic acid-induced writhing by 52% (p<0.01) and 85% (p<0.001), respectively, and RA at 100mg/kg also caused significant inhibition of formalin-induced pain in the early and late phases (p<0.01 and p<0.001, respectively). RA at 100mg/kg significantly suppressed carrageenan-induced paw edema at 3, 4, 5 and 6h after carrageenan injection (p<0.01, p<0.05 p<0.01, and p<0.05, respectively) and showed significant activity against PGE2-induced paw edema. RA at 100mg/kg also inhibited cotton pellet-induced granuloma formation in mice. Taken together, these results demonstrate that RA possesses both central and peripheral antinociceptive activities and has anti-inflammatory effects against acute and chronic inflammation. While further evaluation regarding the safety profile of RA is needed, these data may provide a basis for the rational use of RA and T. laurifolia for treatment of pain and inflammatory disorders.