ABSTRACT
Aim: To investigate anti-inflammatory and antinociceptive potentials of aqueous stem bark extract of Khaya senegalensis A. Juss (Meliaceae) in rodents. Methodology: Anti-inflammatory activity of aqueous stem bark extract of K. senegalensis (AKS) was studied in different models. Effect of the extract in acute inflammation was tested in carrageenan-induced rat paw edema and its effect in chronic inflammation was evaluated using cotton pellet-induced granuloma test. Croton oilinduced ear edema in mice was used to investigate the effect of the extract on topical inflammation. Antinociceptive property of AKS was evaluated using three models of nociception: hot-plate test, acetic acid-induced writhing in mice and formalin-induced paw licking in rats. Membrane stabilizing effect of AKS was tested in heat and hypotonicity-induced hemolysis. The mechanism of antinociceptive effect of the extract was evaluated by pre-treating rats with metoclopramide, a dopamine (D2) antagonist (1.5 mg/kg body wt.) and naloxone, an opioid receptor antagonist (5 mg/kg body wt.). One hour after these treatments, the rats were given AKS (150 mg/kg p.o) and their reaction time in hot-plate was assessed. Free-radical scavenging activity of the extract was measured by decrease in the absorbance of 1, 1-Diphenyl-2-picrylhydrazyl (DPPH) methanol solution. Results: The extract produced significant (P<0.05) and dose-dependent inhibition of ear edema in mice. It also caused a significant (P<0.05) reduction in granuloma formation and paw edema in rats. At concentration range of 125 - 500 μg/ml, AKS significantly (P<0.05) protects the erythrocyte membrane against lysis induced by heat and hypotonic medium. It also significantly (P<0.05) reduced the licking/biting time of the formalininjected rat paw in the early (19 - 51 % reduction) and late (13 - 57 % reduction) phases. The extract demonstrated significant (P<0.05) antinociceptive activity in the hot-plate and writhing tests and exhibited good scavenging effect on DPPH free radical. Conclusion: The study demonstrated that Khaya senegalensis stem bark aqueous extract possesses anti-inflammatory activity and antinociceptive effect mediated via central and peripheral mechanisms. Further studies on the plant may produce lead molecules for the development of new anti-inflammatory drugs.
ABSTRACT
Aims: To study anticonvulsant and central nervous system depressant activity of methanol leaf extract of Croton zambesicus (MECZ) in Swiss albino mice and investigate the role of serotonin in these activities. Methodology: Anticonvulsant activity of graded doses (200, 300 and 400 mg/kg p.o) of MECZ was assessed through seizures induced by picrotoxin and pentylenetetrazole (PTZ). Effects of the extract on pentobarbitone-induced sleep and amphetamine-induced stereotype behavior were also evaluated. Possible involvement of serotonergic pathways was studied using cyproheptadine (4mg/kg i.p), a non-selective serotonin antagonist (5-HT1/5HT2). Results: In both picrotoxin and PTZ-induced seizures, the extract significantly delayed onset of seizure (p<0.05) in a dose-dependent manner and provided significant protection against death. There was a dose-dependent increase of pentobarbitone sleeping time and a significant reduction (p<0.05) in the sleep latency. The extract also produced a significant reduction in amphetamine-induced stereotype behavior. Pretreatment with cyproheptadine abolished the anticonvulsant effect of the extract. The inhibitory effect of the extract on amphetamine-induced hyperactivity and its potentiation of pentobarbitone-induced sleep were also reversed by cyproheptadine. Conclusion: The results of this study showed that methanol extract of Croton zambesicus leaf possesses anticonvulsant activity and other CNS depressant activities and these activities are possibly mediated through interaction between serotonergic and GABAergic transmissions.