Volume 19, Issue 44, July - December, 2025

Comparative evaluation of the functional properties of natural and modified African Bitter Yam (Dioscorea dumetorum) starch as potential excipients in drug formulations

Moriyike Makinde¹, Oladapo Adetunji^1,2♦, Babatunde Samuel^1,3

¹Centre for Drug Discovery, Development and Production, Faculty of Pharmaceutical Sciences, University of Ibadan, Ibadan, Nigeria.
²Department of Pharmaceutics and Pharmaceutical Technology, Faculty of Pharmaceutical Sciences, University of Ibadan, Ibadan, Nigeria.
³Department of Pharmaceutical and Medicinal Chemistry, Faculty of Pharmaceutical Sciences, University of Ibadan, Ibadan, Nigeria

^♦Corresponding author
Dr Oladapo Adetunji: Department of Pharmaceutics & Pharmaceutical Technology, and Centre for Drug Discovery, Development and Production, Faculty of Pharmaceutical Sciences, University of Ibadan, Ibadan, Nigeria

ABSTRACT

The purpose of modifying native starch is to enhance its role in drug delivery. African Bitter Yam starch (ABY) was modified physically by pregelatinization to yield PABY and chemically using both citric and phosphoric acid to obtain CAMABY and PMABY respectively. Functional properties of the starches as potential excipients were then compared. The four starch samples were categorized using photomicrography, density measurements, flow properties (angle of repose), swelling and pasting properties, and Fourier Transform Infrared (FTIR) spectroscopy as assessment criteria. Results were analysed using mean (n=3), standard deviation and analysis of variance, ANOVA (p<0.05). Photomicrography revealed that the starch samples were spherical in shape. ABY starch particles appear more tightly packed with fewer void spaces. PABY, CAMABY and PMABY showed agglomeration of the starch granules and increased pore spaces. Deformation characteristics of the modified starches (measured by Carr’s index) were significantly better than the native starch, however, PABY had the highest bulk density (0.59±0.021). The angle of repose ranked ABY(48.180)>PMABY(39.610)>CAMABY (36.230)>PABY(25.970), indicating that phosphorylation conferred better flow properties. The swelling properties ranked CAMABY(1.47±0.08)>PMABY>PABY> ABY(0.76±0.02). Significant differences were observed in the pasting properties of the starches, with PMABY and CAMABY having the highest (131.02 cP) and lowest (12.13cP) breakdown viscosity, respectively, implying the highest degree of substitution in PMABY. Characteristic FTIR peaks of ABY at 784.80 cm-3 and 1330.40 cm-3 were also observed for PABY, CAMABY and PMABY, which showed additional peaks due to the modifications, but maintained the basic structure of the native starch. This study showed that physical and chemical modification showed substantial improvements on the functional properties of the native African Bitter Yam starch. The chemical modification methods adopted in this study can be further exploited for use in other polymers, with physicochemical parameters tested as well as other parameters predictive of improved desirable excipient properties

Keywords: Starch, Excipients, African Bitter Yam, Pregelatinization, Chemical modification.

Drug Discovery, 2025, 19(44), e22dd3015

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Published: 16 October 2025