Assessment of the release rate and toxicity of zinc compounds used in pharmaceuticals and cosmetics

The degree of release from ointments and the toxicity of three zinc compounds were assessed to establish their minimum sufficient concentration in antibacterial pharmaceutical and cosmetic products. The properties of zinc oxide (ZnO), zinc pyrrolidone carboxylate (ZnРСА) and zinc salicylate (Zn(Sal)2·2H2О) were compared. The release rate of active substances from petrolatum-based ointments (the mass fraction of zinc compounds is 1%) was determined by the Kruvchinsky method. A cellophane film for dialysis served as a semipermeable membrane, which was fixed on a glass tube (length 15 cm, cross section 20 mm2). A sample of ointment (2.00 g) was applied to the inner surface of the membrane. The dialysis tube was inserted into a beaker with dialysis medium and immersed to a depth of no more than 3 mm. The toxicity of aqueous solutions (distilled water) of zinc compounds was determined in a bioluminescent biotest using “Ecolume” bacterial preparation based on a non-pathogenic strain of Escherichia coli. It was found that a high level of toxicity of is achieved at 10-5 mol/dm3 zinc salts in a solution, zinc oxide – 10-4 mol/dm3. A similar amount of Zn2+ diffuses from ointments through a semipermeable cellophane membrane used for the study of dialysis into a 50% aqueous alcohol solution. Zinc ion release from ointment with ZnO was only 0.31%, as well as from ointments with ZnPCA and Zn(Sal)2·2H2О – 1.59% and 1.87% respectively. Thus, the tested approach is economically and environmentally effective, as it allows you to determine the lowest effective concentration of active substances, reducing the burden on the human microbiome and the environment.