Nirajan Bhusal, Pharkphoom Panichayupakaranant, and Wantana Reanmongkol

pp. 325 - 331

Abstract

Rhinacanthus nasutus (R. nasutus) leaf extract was prepared and standardized to obtain rhinacanthins rich extract
that contained total rhinacanthin-C (Rn-C) of not less than 70% w/w. Rn-C was also isolated from the standardized R. nasutus
leaf extract (SRLE). SRLE was investigated on pain and inflammatory models in parallel with its main naphthoquinone
constituent, Rn-C in order to compare their efficacy in experimental animals. The analgesic activities of SRLE and Rn-C were
evaluated by the acetic acid-induced writhing test, a hot-plate test and formalin test at doses of 20, 40, and 80 mg/kg. The
anti-inflammatory activities were investigated by carrageenan induced paw edema and the cotton pellet induced granuloma
in rats at doses of 80, 160, and 320 mg/kg. SRLE and Rn-C inhibited the acetic acid induced writhing in a dose dependent
manner; inhibited the early phase of the formalin test at 80 mg/kg and the late phase at 40 and 80 mg/kg. However, none of
the tested doses were effective in protecting against the hot plate test. In the animal models of inflammation, SRLE and Rn-C
dose dependently inhibited edema formation in the carrageenan induced paw edema and suppressed granuloma formation in
the cotton pellet induced granuloma in rats. The effects of SRLE in these tests were similar to those of the Rn-C. This study
confirms the analgesic and anti-inflammatory activities of SRLE and Rn-C in animal models as well as demonstrating that they
have a similar efficacy.