An evaluation of the pharmaceutical properties of the Nigerian baobab polysaccharide for sustained release oral tablets

Abstract

Natural polysaccharides have various applications, and their use is on the rise due to properties including biodegradability, biocompatibility, cytocompatibility and the absence of negative immune responses. Natural polysaccharides have also been reported to be efficient biopolymers that can be used in oral dosage forms. To this end, this study investigated the potential of using the Nigerian baobab polysaccharide as a renewable pharmaceutical excipient and its impact on the release of theophylline as a model drug. The results indicate that the extraction process yielded an amorphous polysaccharide from the baobab oblong fruit. The thermogravimetric analysis showed weight loss to occur in three phases typical of polysaccharide decomposition. Differential scanning calorimetry (DSC) revealed that the polysaccharide was stable until around 175 °C, after which thermal degradation takes place. Tablet formulations containing different concentrations of baobab were evaluated for mechanical properties, flowability, and dissolution characteristics. An increase in baobab content improved the mechanical strength of the tablets. The increase in the baobab concentration simultaneously brings about a decrease in the porosity of the compacts from 11% to 9%, demonstrating its suitability for use in tablet formulations. In vitro dissolution studies in acidic media (pH 1.2) showed that formulations with higher baobab content (30%–57.5%) demonstrated sustained release characteristics, with no burst release observed. At pH 6.8, however, an increase in the polysaccharide content seemed to promote a “burst release”. These distinctive behaviours at different pH values suggest significant potential for exploiting and understanding the functional properties of the polysaccharide to aid formulators in manipulating drug release. These pH-dependent behaviours mean that a formulator can tune release by adjusting the baobab : MCC ratio. Higher baobab content (30–57.5%) enables sustained, burst-free release at pH 1.2, while at pH 6.8, increasing baobab (to B4) enhances the 10 min burst, and the baobab-only formulation (B5) achieves the fastest overall release through rapid erosion.