Allantoin eutectics with choline chloride and zinc chloride: interactions and wound healing applications

Abstract

Allantoin eutectics with choline chloride (ACM) and zinc chloride (AZM) are reported. The solid–liquid phase diagram showed the eutectic point in allantoin-rich region (Xallantoin = 0.9) for ACM. In AZM, the eutectic formation occurred in the equimolar mixture. The H-bonded template in pure allantoin was disrupted upon addition of choline chloride or zinc chloride, which led to freezing point depression. Classical and non-classical hydrogen bonding, electrostatic and donor–acceptor interactions existed among the components. Infrared vibrational frequencies indicated the involvement of ureido NH2, and ring carbonyl of allantoin, OH group of choline chloride, and Zn2+ in interactions. Thermogravimetric analysis showed that among equimolar mixtures ACM5 was more stable than AZM5. An increase in zinc chloride content markedly altered the thermal stability in AZM. Both categories of eutectics were universally soluble in dimethyl sulfoxide. Skin wounds in rabbit models were healed more effectively by concoctions containing relatively smaller percentages of eutectics.