Peripheral Analgesic and Anti-Inflammatory Effects of Smilax canariensis in an Animal Model

Smilax canariensis Brouss. ex Willd. is an endemic plant of the Canary Islands. Its rhizomes, leaves and stems have been traditionally used in Canary folk medicine to treat a wide variety of conditions including pain. Our objective is to investigate the analgesic and anti-inflammatory activities of different extracts of S. canariensis in Swiss mice, using established biological models for pain and inflammation, such as phenylquinone writhing test, formalin test, tail-flick test and mouse paw edema induced by carrageenan. Oral administration of S. canariensis extracts significantly reduce writhing episodes evoked by phenylquinone injection in a dose-dependent manner; and higher doses result in a reduction of pain similar to or higher than that of the reference drug piroxicam (59.56%; p < 0.01). The extracts also cause a marked dose-dependent inhibition of for-malin-induced pain in the second phase but only minimal inhibition of tail-flick behavior, suggesting that S. canariensis is not a centrally acting analgesic. Finally, in the carrageenan-induced hind paw edema model, the extracts show a moderate anti-inflammatory effect, the most active being the ethyl acetate fraction at 200 mg/kg p.o. (33.33%; p < 0.05). Our results suggest that S. canariensis extracts have clear dose-dependent peripheral analgesic effects, which lends support to the traditional use of this medicinal plant to treat pain associated with inflammatory or other processes.