Anti-allodynic and Anti-hyperalgesic effects of an ethanolic extract and xylopic acid from the fruits of Xylopia aethiopica in murine models of neuropathic pain

BACKGROUND: Fruit extracts of Xylopia aethiopica are used traditionally in the management of pain disorders including headache and neuralgia. An animal model of vincristine-induced sensory neuropathy was developed after repeated intraperitoneal injection in rats and used in the present work to study the effects of the ethanolic extract of X. aethiopica (XAE) and its diterpene xylopic acid (XA) in vincristine-induced neuropathic pain. MATERIALS AND METHODS: Vincristine (0.1 mg kg(-1) day(-1)) was administered during two cycles of five consecutive days to induce chemotherapy-induced neuropathic pain. Static tactile anti-allodynic, anti-hyperalgesic, and cold anti-allodynic effects of XAE (30-300 mg kg(-1)) and XA (10-100 mg kg(-1)) were assessed using Von Frey filaments of bending forces of 4, 8, and 15 g, the Randall-Selitto paw pressure test, and cold water (4.5°C), respectively. RESULTS: Administration of vincristine caused the development of allodynia and hyperalgesia with no significant motor deficit, spontaneous pain, and foot deformity. XAE (30-300 mg kg(-1)) and XA (10-100 mg kg(-1)) exhibited anti-hyperalgesic, tactile, and cold anti-allodynic properties with XA exhibiting greater potency than XAE. Pregabalin (10-100 mg kg(-1)) used as control produced similar effect. CONCLUSION: These findings establish the anti-allodynic and anti-hyperalgesic effects of the ethanolic fruit XAE and its major diterpene XA in vincristine-induced neuropathtic pain.