Category: Formulation and Quality
Purpose: Starch is a carbohydrate polymer that is widely abundant in nature, and has been found useful in the pharmaceutical industry as excipients in formulations. The usefulness of Starch in the pharmaceutical industry is due to its low cost, non-toxic and biodegradable nature. Starches are modified either physically, chemically or enzymatically to suit application in the industry. In this study, starch from Digitaria exilis was characterized, modified and used as a disintegrant in tablet formulation.
Methods: Native Starch (NS) was isolated from Digitaria exilis seed, modified by pre-gelatinization (PGS) and the prgelatinized starch was treated chemically to obtain prgel-carboxymethylated starch (PCMS). The starches were characterized by scanning electron microscopy (SEM), Fourier Transform Infrared, X-ray diffractometer (XRD), pH, swelling index, moisture content, density and flow properties. The starches were used as disintegrant at 5% and 10% w/w concentrations in paracetamol tablet formulations and mechanical and release properties of tablets were analysed and compared with corn starch (CS). Statistical analysis using Anova was carried out with computer software graph pad prism (Graph pad software INC. San Diego, USA). At 95% confidence intervals, p value less than or equal to 0.05 were considered significant.
Results: The bulk density of the starches was between 0.95 g/mL and 1.03 g/mL. The angle of repose ranged from 22.60o to 36.90o, while the ranking was NS > PGS > PCMS. Hausner’s ratio was 1.05 to 1.08; Carr’s index was 4.55% to 7.77%. The flow properties of the starches improved with modification. The moisture content was 10% - 11.65%, swelling capacity was 120.31% - 138.45%. The XRD indicates the starches were crystalline, though the degree of crystallinity reduced with modification. The SEM showed polygonal particle shapes with reduced particle size after modification. Tablet friability which ranged from 0.43% to 1.75% ranked PGS < NS < CS < PCMS. Also, there was significant difference (p< 0.05) in the disintegration time which ranged from 0.58 to 25.01 mins and ranked PGS < NS = CS < PCMS.
Conclusion: Digitalis exilis starch compared favourably as a disintegrant with corn starch, pregelatinization of this starch (PGS) improved the disintegration power. The flow property of native starch was greatly improved after carboxymethylation, which could also be explored as a directly compressible excipient.