Anti-Inflammatory and Anti-Nociceptive Activities of Stem-Bark Extracts and Fractions of Carpolobia Lutea (Polygalaceae)

Background: In Niger Delta, ethnomedicine hydroalcoholic extract of Carpolobia lutea (CL) (Polygalaceae) is used to relieve inflammatory pains. Objectives: The purpose of this study is to evaluate the anti-inflammatory and antinociceptive effects of ethanolic stem extract (ESE) and to fractionate the ESE for the elucidation of bioactive molecules. Materials and Methods: The antinociceptive effects for ESE were tested against two noxious stimuli; chemical (acetic acid-induced writhing and formalin-induced pain) and thermal (hot plate) stimuli. The effects of paracetamol (130 mg/kg), indomethacin (10 mg/kg), and morphine (5 mg/kg) pretreatment were investigated. To isolate the bioactive compounds with anti-inflammatory effect, two doses (86.6 and 173.2 mg/kg) of four fractions (methanol fraction MTF, ethyl acetate fraction EAF, chloroform fraction CHF, and n-hexane fraction n-HF) obtained from fractionating ESE were utilized. Carrageenan, egg albumin, and capsaicin-induced edema of the hind paw of the rats were the models adopted. Paw volume was measured by a digital vernier caliper from 0 to 6 h after injection. This was compared to standard drugs. The results were subjected to statistical analysis. Results: The ESE decreased significantly (P < 0.001) the writhing of acetic acid-induced abdominal contractions and licking of formalin-induced pains but does not have any effects on the hot plate test. Of the four fractions obtained, the EAFs demonstrated a significant (P < 0.001) inflammatory inhibition of 98.97% and 41.91% at 86.6 and 173.2 mg/kg, respectively, compared to 65.75% inhibition demonstrated by the reference drug, acetylsalicylic acid (100 mg/kg) on the carrageenan model while 36.36% and 29.87% inhibition of inflammation at 86.6 and 173.2 mg/kg, respectively, on the egg albumin models; there was no significant effect on the capsaicin model. Conclusion: The isolation of quercetin and kaemferol from CL gave credence to its anti-inflammatory and antinociceptive effects.