Analgesic and anti-inflammatory properties of the leaf extracts of Anacardium occidentalis in the laboratory rodents

Anacardium occidentalis (family: Anacardiaceae) is a plant of the tropical climate widely used by folklore to treat pain and inflammation. This study was conducted to evaluate the analgesic and anti-inflammatory effects of the leaf extracts in rat and mice using different models in other to confirm folkloric claims. The aqueous, hexane, dichloromethane and methanol extracts (AEAO, HEAO, DEAO and MEAO respectively) were investigated for analgesic effects in acetic acid induced pain in mice. They significantly reduced the number of writhing (p<0.001) and the highest analgesic effect was seen in DEAO extract. DEAO was further studied on various analgesic and anti-inflammatory models in graded doses. The extract significantly reduced writhing induced by acetic acid and the number and time of paw licking induced by formalin (P < 0.05) in a dose related manner. It inhibited the neurogenic and inflammatory phases of formalin (P < 0.05). Analgesia was shown in the inhibition of nociception induced by tail immersion in 55oC hot water. The extract prolonged the latencies of tail withdrawal to a similar degree as pentazocine. The extract caused significant inhibition of carrageenan induced paw oedema in rats (P < 0.05) in a dose dependent manner. These findings suggest that the leaf extracts of Anacardium occidentalis are highly potent analgesic and anti-inflammatory agents. Phytochemical analysis showed that the leaf extracts contain alkaloids, tannins, saponins and cardenolides