ACETYLATION AND CHARACTERIZATION OF ENSET STARCH AND EVALUATION OF ITS DIRECT COMPRESSION AND DRUG RELEASE SUSTAINING PROPERTIES

Enset (Ensete ventricosum, Musaceae), a plant widely cultivated in south and southwest of Ethiopia, has been shown to be a rich source of starch. In an effort to produce directly compressible matrix-forming excipient, native enset starch was acetylated. Starch acetates (SA) with degrees of substitution (DS) of 0.672 and 2.142 were evaluated. Fourier transform infrared (FTIR) spectra of the modified starches verified the acetylation of the starch molecules. Further investigations revealed that acetylation increased swelling power and solubility, improved flow property and compactability of the starch. The tensile strength of SA matrix tablets increased with an increase in DS. Plain tablets of SA with DS 0.672 disintegrated within 3 min while those of SA with DS 2.142 did not disintegrate over a period of 2 h. Dissolution studies of theophylline loaded SA tablets conducted in 0.1 N HCl for the first 1.5 h and in phosphate buffer pH 6.8 for the remaining study time revealed the change in drug release rate from rapid to sustained release (>12 h) as the DS increased from 0.672 to 2.142. The dissolution data obtained best fitted Higuchi model with R² > 0.99. The drug release diffusional exponent (n), obtained from Korsemeyer-Peppas model, varied between 0.4899 – 0.6369 for different theophylline/SA ratios and the goodness of the fit was > 0.99 in each case which indicated the deviation from Fickian diffusion. Accordingly, high degree of acetylation renders enset starch highly compressible and suitable for sustained release formulations that makes it amenable for use as an alternative pharmaceutical excipient.