Isolation, chemical characterization, evaluation of analgesic and anti-inflammatory activities of triterpenoids from the tubers of raphionacme vignei E. A. Bruce (Apocynaceae)

Abstract

Raphionacme vignei E. A. Bruce (Apocynaceae) is a plant of the traditional African pharmacopoeia, whose parts are used in the treatment of various pathologies. Water-soaked R. vignei tubers are edible. The objective of this study was to isolate triterpenoids from the acetonic extract of R. vignei tubers, evaluate the analgesic and anti-inflammatory activities of each molecule. The isolated compounds, characterized by NMR and mass spectrometry, is composed of six triterpenoids: beta-amyrin dodecanoate 1(DDQ1), lupeol dodecanoate 2(DDQ2), beta-amyrin acetate 3(DDQ3), lupeol acetate 4(DDQ4), lupeol 5 (DDQ5) and β-sitosterol 6(DDQ6). These molecules (DDQ2, DDQ3, DDQ4, DDQ5, DDQ6) are anti-inflammatory in carrageenan induced rat paw edema, with better anti-inflammatory power for DDQ2 and DDQ4, which would be related to the presence of acetate function and cycle E. DDQ2 and DDQ4 are also analgesic in acetic acid induced contortions and the removal test of rat tail on the heating plate. The analgesic action of DDQ2 and DDQ4, superior to that salicylic acetyl acid, identical to that morphine, suggests a central action of these two molecules. The potent analgesic effect of DDQ2 and DDQ4, could be attributed to the presence of cyclopentane and isoprene substitution in position 19 of the lupane family. DDQ2 and DDQ4 represent a potential for the synthesis of structural analogues with analgesic and/or anti-inflammatory properties.