Antinociceptive effects of an extract, fraction and an isolated compound of the stem bark of Maytenus rigida

The antinociceptive activity of the Maytenus rigida Mart. (Celastraceae) ethanol extract and its ethyl acetate fraction as well as of (-)-4'-methylepigallocatechin (1), a previously isolated compound, was demonstrated in vivo. ED50 for 1 in the writhing test was 14.14 mg/kg. The acetic acid-induced writhing was inhibited by 98.4, 84.4, and 58.3%, respectively, when mice were treated with the ethanol extract, ethyl acetate fraction, and 1. In the hot plate test, mice pretreated with 1 showed significantly increased reaction times (60-89%). Oral administration of 1 significantly inhibited first and second phases of the formalin-induced pain (50 and 26.5%, respectively), whereas indomethacin inhibited only the second phase of the test (41.2%). Ethanol extract and its fraction showed effects on inflammatory pain, while neurogenic and inflammatory pain suppression by 1 is a strong indication of the presence of both central and peripheral effects and suggests its analgesic and anti-inflammatory potential.