Synthesis, characterization and evaluation of release retardant modified starches of Lagenaria siceraria seeds

Starch isolated from under-utilized seeds of five different cultivars of Lagenaria siceraria (Mol.) standley (Cucurbitaceae) was carboxymethylated. The influence of the degree of substitution (DS) on physicochemical properties and drug release properties of starches was studied. The physicochemical profiles of the derivatives were assessed by means of FT-IR, XRD, SEM, elemental analysis, reaction efficiency, water binding capacity, swelling power, powder characteristics and visual estimation. The highest values of the DS obtained when the carboxymethylation was performed at 45 °C for 4 h. Scanning electron microscopy (SEM) showed that after carboxymethylation, the granular appearance of the native starch was distorted. The new bands at 1576.87 cm−1 and 1423.81 cm−1 in Fourier transform infrared (FT-IR) indicated that the starch granules were substituted. Wide-angle X-ray diffractometry revealed that crystallinity was reduced significantly after carboxymethylation. Powder studies revealed that these starches possess potential for pharmaceutical applications. The matrix tablets were found to release the drug by Korsmeyer and Peppas kinetics. The carboxymethylated starches with high DS can be used as a drug release retardant in sustained release formulations, as the drug dissolution rate of native starches was significantly lower than the modified starches.