21­Benzylidene digoxin, a novel digoxin hemi-synthetic derivative, presents an anti-inflammatory activity through inhibition of edema, tumour necrosis factor alpha production, inducible nitric oxide synthase expression and leucocyte migration.

Recent findings have demonstrated new therapeutic functions of cardiotonic steroids, a process that is termed drug repositioning. Despite the confirmed anti-inflammatory effects of cardiotonic steroids, their clinical use has been discouraged due to toxicity related to inhibition of the Na+/K+ ATPase. A novel synthetic compound derived from digoxin, 21­benzylidene digoxin (21­BD), does not inhibit this enzyme. Herein, we evaluated the anti-inflammatory and antinociceptive effects and acute toxicity of 21­BD. Murine (Swiss mice) models of paw oedema induced by carrageenan, acetic acid-induced abdominal writhing, and formalin and acute toxicity tests were used. Oral administration of 21­BD (0.3 mg/kg) showed a significant and prolonged inhibition of paw oedema. Histological analysis demonstrated a reduction in inflammatory cells and expression of inducible nitric oxide synthase (iNOS) in footpads 6 h after administration of carrageenan. 21­BD (0.3 mg/kg) also reduced the levels of tumour necrosis factor (TNF)-α 2 and 4 h after carrageenan. 21­BD demonstrated antinociceptive activity, inhibiting abdominal writhes at all tested doses. However, in the formalin test, 21­BD did not present antinociceptive activity. In the acute toxicity test, 21­BD did not cause symptoms of toxicity or mortality. The present study demonstrated, for the first time, that 21­BD is safe and exhibits a marked anti-inflammatory activity in acute local inflammation. This effect might be a consequence of its ability to inhibit the release of the PMN leucocyte-derived mediators, including TNF-α, and iNOS expression as well as its inhibitory effect on oedema and PMN leucocyte infiltration.