Starch extracted from KJ CMU-107 rice, with amylose content of 13.4%, was modified to yield pre-gelatinized starch (PGS), carboxymethyl starch (CMS), crosslinked carboxymethyl starch (CLCMS), crosslinked starch (CLS), and hydroxypropyl starch (HPS). Their physicochemical properties were assessed in comparison with the native starch (NS), and their functional properties were then evaluated for potential use as pharmaceutical excipients. Scanning electron microscopic (SEM) images and X-ray diffraction (XRD) patterns showed that granules of all but one of the modified starches retained the native character and crystalline arrangement. The exception, PGS, exhibited extensive granular rupture, which correlated with the loss of crystallinity suggested by the amorphous halo in XRD. Energy-dispersive X-ray (EDX) data confirmed the modification by the presence of related elements. Carboxymethylation increased solubility in unheated water, while crosslinking improved swelling. All modified starches displayed improved oil absorption capacity by 17-64%, while CMS and CLCMS also exhibited significant moisture sorption at above 75% RH PGS and HPS exhibited lower gelatinization temperature (Tg) and enthalpic change (ΔH), while CLS showed higher Tg and ΔH. CMS, CLCMS, and CLS showed adequate powder flow and compactibility, qualifying as potential tablet excipients. The 5% w/v solutions of CMS, CLMS, and HPS also formed intact films with suitable tensile strength. Overall, modified starches derived from KJ CMU-107 could potentially be developed into new pharmaceutical excipients.
Keywords: chemical modification; pharmaceutical excipient; physicochemical property; pre-gelatinization; rice starch.