Biodegradable Polymer Hydrogels Based in Sorbitol and Citric Acid for Controlled Release of Bioactive Substances from Plants (Polyphenols)

Background: Polyphenols are secondary metabolites of plants which are generally associated with the protection against ultraviolet radiation and aggression by pathogens. Epidemiological studies suggest that long term consumption of diets rich in plant polyphenols offer protection against different diseases with positive effects in the context of human health. Objective: The objective of this work was to develop biodegradable polymer hydrogels (HGs) based in sorbitol and citric acid for controlled release of bioactive substances from plants (specifically strictinin). Method: HGs were synthesized at two relation sorbitol:citric acid (1:1 and 1:2) and characterized by ATRFTIR. In addition, it was determined its water absorption capacity by tea bag method. Hydrolysis of strictinin was studied at different pH and release of strictinin was monitored by UV-vis. Antimicrobial activity of strictinin in solution and in the HGs was tested against E. coli and S. aureus. Results: HGs can be synthesized from sorbitol and citric acid by free-solvent synthesis. These HGs can be used for the release of strictinin at acid pH without changes in its chemical structure; at alkaline pH, hydrolysis processes affect its strictinin chemical structure. Diffusion of strictinin is slower in HG 1:1 than HG 1:2, being the released quantity by diffusion in both cases are the same. In addition, only 29.8 % of strictinin can be release by diffusion and, in consequence, the remaining strictinin must be released by other mechanism. Conclusion: Results evidence that E. coli and S. aureus are sensitive to low strictinin concentrations (2.43 mgL-1) released from HGs.