Abstract

Diospyros mespiliformis Hochst (Ebenaceae) stem bark is used in traditional medicine for the management of pain related ailments. Several bioactive compounds have previously been isolated from the plant material that includes pentacyclic triterpenes.  This study sequentially extracted and carried out a bioassay-guided fractionation of the plant crude material with solvents of varying polarity using analgesic efficacy in rats as bioactivity marker, aimed to isolate the active constituent. Powdered stem bark of the plant was sequentially extracted with hexane, chloroform and methanol; and preliminary tested for analgesic activity. The chloroform extract being the most active amongst the three extracts was subjected to column chromatography, and a fraction was eluted with mixture of hexane and ethyl acetate (50:50%) which yielded a compound. Three dose levels (25, 50 and 100 mg/kg) of the compound were administered orally to rats.  Acetylsalicylic acid (100 mg/kg, p.o.) was used as the positive control. Nociception was induced mechanically using analgesy meter, and chemically with formalin. The compound alleviated the pain stimulus induced by the analgesy-meter and formalin in rats. The isolated compound was identified as lupeol using thermo-analysis (DSC), colorimetric, chromatographic and spectrometric techniques that included: UV-visible, IR, and ¹³C- and ¹H NMR. It was concluded that lupeol acting alone or synergistically might be responsible for the beneficial effect of the plant in treatment of pain related ailments.

Key words: Diospyros mespiliformis, lupeol, analgesic.