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 b 0.001) antinociceptive activity in the hot-plate test and this effect was reversed by naloxone.
RA at doses of 50 and 100 mg/kg significantly reduced acetic acid-induced writhing by 52% (p b 0.01) and 85%
(p b 0.001), respectively, and RA at 100 mg/kg also caused significant inhibition of formalin-induced pain in
the early and late phases (p b 0.01 and p b 0.001, respectively). RA at 100 mg/kg significantly suppressed
carrageenan-induced paw edema at 3, 4, 5 and 6 h after carrageenan injection (p b 0.01, p b 0.05 p b 0.01, and
p b 0.05, respectively) and showed significant activity against PGE2-induced paw edema. RA at 100 mg/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.