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.
Keywords: Acanthaceae; Anti-inflammatory activity; Antinociceptive activity; Rosmarinic acid; Thunbergia laurifolia.
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