In this study, Ethanolic extracts of Allophylus cobbe showed effectiveness against various experimental animal models of pain and inflammation. Allophylus cobbe extract significantly inhibited the nociception produced by hot plate and inhibited the acetic acid-induced writhing significantly. Allophylus cobbe extract also significantly attenuated carrageenan-induced rat right hind paw oedema. Moreover, HPLC-DAD analysis of Allophylus cobbe extract confirmed the presence of anti-inflammatory phenolic compounds.
Earlier investigators suggested that acetic acid writhing and hot plate tests are used to evaluate peripherally and centrally acting analgesic drugs respectively (Kosteret al 1959; Williamsonet al 1996). Pain induced by thermal stimulus of the hot plate is specific for centrally mediated nociception (Amabeoku and Kabatende 2012). The ability of A cobbe extract to prolong the reaction latency to pain thermally-induced in mice by the hot plate suggests central analgesic activity.
The acetic acid induced abdominal constriction method is widely used for the evaluation of peripheral antinociceptive activity (Kosteret al 1959; Silva et al 2013). It is very sensitive and able to detect anti-nociceptive effects of compounds at dose levels that may appear inactive in other methods like the tail-flick test. Generally, acetic acid produced writhing or nociception by stimulating the production of prostaglandin (Satyanarayana et al 2004). Local peritoneal receptors are postulated to be partly involved in the abdominal constriction response (Correa and Calixto 1993; Mbiantcha et al 2011). The method has been associated with prostanoids in general, e.g. increased levels of PGE2 and PGF2α in peritoneal fluids as well as lipoxygenase products (Duarte et al 1988; Khan et al 2010). Therefore the results of the acetic acid induced writhing; strongly suggest that the mechanism of action of this extract may be linked partly to lipoxygenases and/or cyclo-oxygenases pathways. The extract at the doses tested was shown to possess anti-nociceptive activity evident in the nociceptive pain model, signifying it possesses both central and peripherally mediated activities.
Carrageenan is the phlogistic agent of choice for testing anti- inflammatory drugs as it is none antigenic and is devoid of apparent systemic effect (Lima et al 2007). Carrageenan model of inflammation is said to be biphasic. In the first phase, histamine, serotonin and kinnins will be released and form nonphagcytic edema in the first hour; while the second phase is attributed to the release of prostaglandins and lysosome enymes in the second to the third hour (Khan et al 2009; Muhammad et al 2012). A cobbe extract inhibited both the first and second phases of inflammation. The ability of the extract to inhibit carrageenan induced paw oedema suggests it possesses a significant effect against acute inflammation. The extract (250 mg/kg) also caused marked inhibition of carrageenan-induced hind paw oedema...