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Item Development of repaglinide microspheres using novel acetylatedstarches of bitter and Chinese yams as polymers(Elsevier B.V., 2016) Okunlola, A.; Adebayo, A. S.; Adeyeye, M. C.Tropical starches from Dioscorea dumetorum (bitter) and Dioscorea oppositifolia (Chinese) yams were acetylated with acetic anhydride in pyridine medium and utilized as polymers for the delivery of repaglinide in microsphere formulations in comparison to ethyl cellulose. Acetylated starches of bitter and Chinese yams with degrees of substitution of 2.56 and 2.70 respectively were obtained. Acetylation was confirmed by FTIR, 1 H NMR spectroscopy. A 32 factorial experimental design was performed using polymer type and drug-polymer ratio as independent variables. Particle size, swelling, entrapment and time for 50% drug release (t50) were dependent variables. Contour plots showed the relationship between the independent factors and the response variables. All variables except swelling increased with drug: polymer ratio. Entrapment efficiency was generally in the rank of Bitter yam > Ethyl cellulose > Chinese yam. Repaglinide microspheres had size 50 ± 4.00 to 350 ± 18.10μm, entrapment efficiency 75.30 ± 3.03 to 93.10 ± 2.75% and t50 3.20 ± 0.42 to 7.20 ± 0.55h. Bitter yam starch gave longer dissolution times than Chinese yam starch at all drug-polymer ratios. Drug release fitted Korsmeyer-Peppas and Hopfenberg models. Acety-lated bitter and Chinese yam starches were found suitable as polymers to prolong release of repaglinidein microsphere formulations.Item Design of bilayer tablets using modified dioscorea starches as novel excipients for immediate and sustained release of aceclofenac soduim(Frontiers in Pharmacology, 2015-01) Okunlola, A.Bilayer tablets of aceclofenac sodium were developed using carboxymethylated white yam (Discorearotundata) starch (CWY)for a fast release layer (2.5, 5.0, and 7.5% w/w), and acid hydrolyzed bitter yam (Dioscoreadumetorum) starch (ABY) for a sustaining layer(27% w/w). Sodium starch glycolate (SSG) and hydroxypropyl methyl cellulose (HPMC) were used as standards. The starches were characterized using Fourier Transform Infrareds pectroscopy(FT- IR), particle size, swelling power, densities and flow analyses. Mechanical properties of the tablets were evaluated using crushing strength and friability while release properties were evaluated using disintegration and dissolution times. Distinctive fingerprint differences between the native and modified starches were revealed by FT-IR. Carboxymethylation produced starches of significantly (p<0.05) higher swelling and flow properties while acid- modification produced starches of higher compressibility. Bilayer tablets containing ABY had significantly higher crushing strength and lower friability values (p<0.05) than those containing HPMC. Crushing strength increased while friability values decreased with increase in CWY. Generally tablets containing the modified Dioscorea starches gave faster (p<0.05) disintegration times and produced an initial burst release to provide the loading dose of the drug from the immediate-release layer followed by sustained release (300±7.56– 450±11.55min). The correlation coefficient (R2) and chi- square (χ2) test were employed as error analysis methods to determine the best- fitting drug release kinetic equations. Invitro dissolution kinetics generally followed the Higuchi and Hixson- Crowell models via a non-Fickian diffusion-controlled release. Carboxymethylated white yam starch anda cid- modified bitter yam starch could serve as cheaper alternative excipients in bilayer tablet formulations for immediate and sustained release of drugs respectively, particularly where high mechanical strength is required.