Prolonged Anti-Inflammatory Activity of Topical Melatonin by Niosomal Encapsulation

Melatonin, encapsulated and non-encapsulated, in a topical gel, was comparatively investigated for its in vitro permeation and in vivo anti-inflammatory properties. An average size of the melatonin-encapsulated niosomes of 197 nm with a zeta potential of-78.8 mV and an entrapment efficiency of 92.7% was incorporated into a gel base. In vitro skin permeation of the same gel base incorporated with non-encapsulated melatonin or melatonin niosomes at 5% was comparatively evaluated through porcine skin using Franz diffusion cells and analyzed by spectroflurometry at λex 278 and λem 348 nm. From the same gel base, the permeation rate of non-encapsulated melatonin was about 2.5 times greater than that of melatonin-encapsulated niosomes. In comparison to piroxicam gel and hydrocortisone cream used as the positive controls, topical applications of melatonin and melatonin niosome gels tested in croton oil-induced ear edema in mice suggested that its anti-inflammatory activities were prolonged by the niosomal encapsulation. Similarly, analgesic effect of melatonin was prolonged by niosomal encapsulation using tail flick test in mice. Therefore, its immediate permeation through the skin was retarded by niosomal encapsulation which could also prolong its rapid decline in exerting anti-inflammatory and analgesic activities in vivo.