The purpose of this study was to isolate starch from the tubers of Cyperus esculentus L. and evaluate its physicochemical and binder properties. Extraction of starch using sodium metabisulfite yielded 37 g of starch per 100 g of the tubers. Scanning electron microscopy indicated that Cyperus starch consists of oval to elliptical particles with a smooth surface. Cyperus starch demonstrates a narrow particle size distribution with a mean of 8.25 μm. Cyperus starch conforms well to United States Pharmacopeia standards established for widely used starches like maize and potato. The X-ray powder diffraction pattern and moisture sorption profile of Cyperus starch were comparable to that of maize starch. Cyperus starch had lower swelling power than maize and potato starch, indicative of stronger associative forces within the granules. Carr's index and Hausner ratio indicate that Cyperus starch should have comparable flow properties with respect to maize and potato starch. Cyperus starch was employed as binder for the formulation of metronidazole tablets. Formulations containing 5%, 7.5%, and 10% Cyperus starch were compared with those containing 10% potato starch. At 10% binder concentration, the tablets containing Cyperus starch exhibited better hardness and negligible friability as compared with those with potato starch. Although the binder concentration had a significant effect on the disintegration time of the tablets, it did not seem to affect the dissolution profile. These results indicate that Cyperus starch provides excellent binding properties without compromising drug release characteristics and should be explored in pharmaceutical formulations.

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The purpose of this study was to elucidate functional properties of starch granules obtained from tubers of Tacca leontopetaloides and compare them to a commercially available maize starch. Scanning electron microscopy (SEM), particle size analysis, Xray powder diffraction (XRPD), gravimetric moisture sorption, and differential scanning calorimetry (DSC) were used to characterize the samples. Tacca starch exhibited a monomodal distribution of irregularly shaped granules with a mean particle size of 2.64 mm. The spherulites of both samples indicated an A-type pattern, with the degree of crystallinity estimated to be 35% for tacca starch and 38% for maize starch. The moisture sorption profile of both samples was analyzed according to the Guggenheim, Anderson and de Boer (GAB) equation. GAB analysis estimated the monolayer coverage for tacca and maize starch to be 0.0928 g/g and 0.0856 g/g, respectively. The gelatinization parameters of tacca starch were found to be 65.57 -68.56 -73.107C while that of maize starch were 67.30 -70.97 -76.257C. The results of DSC studies indicate that the associative forces that stabilize the granule structure in tacca starch are weaker than those in maize starch. The results obtained in this study establish the fundamental characteristics of tacca starch and suggest that further exploration of its potential for use in a variety of fields is warranted.

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Avocado starch was extracted from the kernels of the fruit Persea americana Miller (Fam. Lauraceae) and evaluated for its potential as an alternative to maize starch as a pharmaceutical excipient. Its physicochemical and thermal properties were evaluated and compared with those of maize starch. Granules prepared with avocado and maize starch pastes as binder were evaluated for their flow, friability and compaction characteristics. The average yield of starch extracted from the fresh kernels of P. americana was 20.5 AE 0.55% w/w. The scanning electron micrograph (SEM) showed that avocado starch has two characteristic granule shapes; triangular and circular both having an approximate equal distribution. The triangular shaped granules are larger (28 to 32 mm) than the circular (6 to 9 mm). The foaming capacity of avocado starch was 19.05 AE 0.6%, its swelling, moisture uptake and paste clarity were generally lower than that of the maize starch. Avocado starch gel exhibited an extent of syneresis after freeze-thaw that increased cumulatively with increase in number of freezethaw cycles. The glass transition (T g ) and gelatinisation temperatures for avocado starch were higher than that of maize starch. The melting temperatures (T m ), ash value, as well as the various densities of avocado starch showed similarities with those of maize starch. The granules prepared with avocado starch pastes as binder showed superior compactibility and mechanical strength to those of maize starch but with similar flow characteristics. Avocado starch generally showed distinct physicochemical and binder properties with some similarities to the standard maize starch.