Modified in vitro release of the chronobiotic hormone melatonin from matrix tablets based on the marine sulfated polysaccharide ulvan

Abstract

In the last decades the paradigm of including excipients in the formulations as inert substances, aiding production processes, has changed and they are now approached as multifunctional compounds. This means that several functions apply, spreading from the stabilization and modified release, to providing biocompatible properties and targeting moieties. In the present work, the algal sulfated polysaccharide ulvan, which remains a rather unexploited biomaterial for applications in the design of drug delivery systems, was used as a formulant in hydrophilic matrix systems, containing the chronobiotic hormone melatonin (MLT). The MLT's in vitro modified release profile in gastrointestinal-like fluids was probed. In general, the % release profile of MLT from ulvan-based tablets, was found to be relatively higher than that of the market drug Circadin® at pH 1.2 (2 h), with the exception of the formulations containing HPMC K15M. The release of most of the ulvan-based formulations follow a sigmoidal pattern (Super Case II mechanism, n > 0.89), which denotes that the drug release is controlled by polymer relaxation and/or erosion.