Effect of pregelatinization and carboxymethylation on starches from African rice and Fonio: Influence on release of low melting-point drug

Abstract

The study investigated the effect of modification on the physicochemical and drug release properties of starches extracted from African rice (Oryzaglaberrima Steud) (AR) and Fonio (Digitariaexilis Stapf) (FR). The starches were modified by pregelatinization and carboxymethylation. The morphology and physicochemical properties of the produced grades of starches were analysed using SEM, RVA, FTIR, P-XRD and DSC. Dissolution was also conducted using a model poorly-soluble drug with low melting point (Ibuprofen). SEM images showed a distinct change in the morphology of the modified starches. Native starch forms had the highest solubility while the carboxymethylated starch forms had the highest water absorbing capacity and swelling index. FTIR and P-XRD confirmed the characteristic functional groups of the starches with their thermal properties demonstrated by DSC. Ibuprofen release from the starch tablets in phosphate buffer (pH 6.8) showed that native AR starch demonstrated similar release profiles with its carboxymethylated form (f2 = 57.5), however, different from the pregelatinised form (f2 = 32.8). Native FR starch demonstrated a different release profile to the carboxymethylated (f2 = 8.6) and the pregelatinised starch forms (f2 = 35.3). Fickian diffusion was the main kinetics of drug release. Modification of these starches can generate polysaccharides with different properties and improved functionalities with a potential for use as alternative pharmaceutical excipients.

Keywords

• starches
• ibuprofen
• matrix tablets
• carboxymethylation
• pregelatinization