Extraction of starch from Solenostemon rotundifolius (Chinese potato) yams, and characterizing by chemical and physical modifications: As novel alternative pharmaceutical excipients

Abstract

Modified starches are developed to decrease any undesirable properties of native starches. Thus, the different kinds of modified starches are used in many industries including the pharmaceutical industry. Solenostemon rotundifolius (Chinese potato), locally known as Innala, is a tuber crop cultivated in Sri Lanka. These tuber yams contain starch over 60% w/w. . This study aimed to characterize the physicochemical properties of modified starches developed from yams of S. rotundifolius to assess their suitability for use as pharmaceutical excipients when compared to maize starch BP. Yams of S. rotundifolius were peeled, sliced, air-dried, and powdered. Starches were extracted by mixing powdered yams with distilled water, filtering, and drying the precipitate at 40 °C. Extracted yam starch was modified chemically by acetylation and physically by pre-gelatinization. The physicochemical parameters, namely, the pH, granule size, bulk, tapped and true densities, Hausner’s ratio, Carr’s index, angle of repose, hydration capacity, moisture sorption capacity, clarity, viscosity, infrared (IR) spectra, X-ray diffraction (XRD) and scanning electron microscopic (SEM) analyses of modified S. rotundifolius starches were evaluated in comparison to maize starch BP. An independent T-test was done to compare data. Acetylated starch provided a characteristic peak in the IR spectrum at 1727.36 cm−1 assigned to C=O assuring acetylation. No new peak formation was observed in pre-gelatinized starch. Maize starch BP and acetylated S. rotundifolius starch exhibited an A-type XRD pattern giving peaks at 2Ɵ angles 150, 170, 180, and 230. Pre-gelatinization changed the XRD pattern. Acetylated starch granules had a dome shape while maize starch granules were polyhedral in shape. Pre-gelatinized starch granules had large flat-shaped granules. All the physicochemical parameters, except Hausner’s ratio and Carr’s index of both acetylated and pre-gelatinized S. rotundifolius starches, were significantly different showing improved physicochemical properties when compared to maize starch BP (p<0.05). Accordingly, these modified starches of S. rotundifolius showed a potential to be explored further as an alternative pharmaceutical excipient.