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

Abstract

The study investigated theeffect of modification on the physicochemical and drug release properties ofstarches extracted from African rice (Oryzaglaberrima Steud) (AR) and Fonio (Digitariaexilis Stapf) (FR). The starches were modified by pregelatinization andcarboxymethylation.  The morphology andphysicochemical properties of the produced grades of starches were analysedusing SEM, RVA, FTIR, P-XRD and DSC. Dissolution was also conducted using amodel poorly-soluble drug with low melting point (Ibuprofen). SEM images showeda distinct change in the morphology of the modified starches. Native starchforms had the highest solubility while the carboxymethylated starch forms hadthe highest water absorbing capacity and swelling index. FTIR and P-XRDconfirmed the characteristic functional groups of the starches with theirthermal properties demonstrated by DSC. Ibuprofen release from the starch tabletsin phosphate buffer (pH 6.8) showed that native AR starch demonstrated similarrelease profiles with its carboxymethylated form (f2 = 57.5), however, different from the pregelatinisedform (f2 = 32.8). Native FRstarch demonstrated a different release profile to the carboxymethylated (f2 = 8.6) and the pregelatinisedstarch forms (f2 = 35.3). Fickiandiffusion was the main kinetics of drug release. Modification of these starchescan generate polysaccharides with different properties and improvedfunctionalities with a potential for use as alternative pharmaceuticalexcipients.