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),  luepol  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.