New Direct Compression Excipient from Tigernut Starch: Physicochemical and Functional Properties

Tigernut starch has been isolated and modified by forced retrogradation of the acidic gel by freezing and thawing processes. Relevant physicochemical and functional properties of the new excipient (tigernut starch modified by acid gelation and accelerated (forced) retrogradation (ST AM )) were evaluated as a direct compression excipient in relation to the native tigernut starch (ST NA ), intermediate product (tigernut starch modified by acid gelation (ST A )), and microcrystalline cellulose (MCC). The particle morphology, swelling capacity, moisture sorption, differential scanning calorimeter (DSC) thermographs and X-ray powder diffraction (XRD) patterns, flow, dilution capacity, and tablet disintegration efficiency were evaluated. The particles of ST NA were either round or oval in shape, ST A were smooth with thick round edges and hollowed center while ST AM were long, smooth, and irregularly shaped typically resembling MCC. The DSC thermographs of ST NA and MCC showed two endothermic transitions as compared with ST A and ST AM which showed an endothermic and an exothermic. The moisture uptake, swelling, flow, and dilution capacity of ST AM were higher than those of MCC, ST A , and ST NA . The XRD pattern and moisture sorption profile of ST AM showed similarities and differences with ST NA , ST A , and MCC that relate the modification. Acetylsalicylic acid (ASA) tablets containing ST AM disintegrated at 3 ± 0.5 min as compared with the tablets containing ST NA , ST A , and MCC which disintegrated at 8.5 ± 0.5, 10 ± 0.5, and 58 ± 0.8 min, respectively. The study shows the physicochemical properties of tigernut starch modified by forced retrogradation as well as its potential as an efficient direct compression excipient with enhanced flow and disintegration abilities for tablets production.