Antinociceptive and anti-inflammatory properties of Tetracera alnifolia Willd. (Dilleniaceae) hydroethanolic leaf extract.

Background Tetracera alnifolia Willd. (Dilleniaceae) is used in traditional African Medicine for the treatment of headache, abdominal pain, and rheumatism. Hence, this study sought to investigate the antinociceptive and anti-inflammatory effects of the hydroethanolic leaf extract of T. alnifolia (HeTA) in rodents. Methods Antinociceptive activity was evaluated using the acetic acid-induced writhing, formalin-/capsaicin-induced paw licking and hot plate tests in mice. The contribution of opioidergic, l-arginine-nitric oxide, and ATP-sensitive potassium channel pathways in HeTA-induced antinociception was also evaluated. The anti-inflammatory effect was assessed using the carrageenan-induced paw edema, xylene ear edema, cotton pellet granuloma, and complete Freund's adjuvant (CFA)-induced arthritis in rats. Results HeTA (100, 200, and 400 mg/kg, p.o.) produced significant (p<0.05) decrease in mean number of acetic acid-induced writhing, time spent licking paw in formalin, and capsaicin tests as well as time course increase in nociceptive reaction latency in hot plate test. HeTA-induced antinociception was prevented by pretreatment of mice with naloxone (non-selective opioid receptor antagonist), l-arginine (nitric oxide precursor), or glibenclamide (ATP-sensitive potassium channel blocker). HeTA (100 mg/kg, p.o.) produced a significant anti-inflammatory effect against carrageenan-induced rat paw edema (1-5 h), xylene-induced ear edema, cotton pellet-induced granuloma formation, and CFA-induced arthritis in rats. The effects of HeTA in various models were similar to the effect of the standard reference drugs. Conclusions Findings from this study showed that HeTA possesses antinociceptive effect possibly mediated through peripheral opioid receptors with activation of l-arginine-nitric oxide and ATP-sensitive potassium channel pathway as well as anti-inflammatory activity.