Starches obtained from four Dioscorea species namely Dioscorea dumetorum (Bitter), Dioscorea oppositifolia (Chinese), Dioscorea alata (Water), and Dioscorea rotundata (White) have been evaluated as binding agents in chloroquine phosphate tablet formulations in comparison with official corn starch. The compressional properties of the formulations were analyzed using density measurements and the Heckel and Kawakita equations. The mechanical properties of the tablets were assessed using tensile strength, brittle fracture index (BFI), and friability tests while the drug release properties of the tablets were assessed using disintegration and dissolution times. The results indicate that the four starches vary considerably in their physicochemical properties. The ranking for the tensile strength and the disintegration and dissolution times for the formulations was Chinese > Bitter > Corn > White > Water while the ranking was reversed for BFI and friability. The results suggest that Water, White, and Corn could be useful when faster disintegration time of tablets is desired while Chinese and Bitter could be more useful when bond strength is of concern and in minimizing the problems of lamination and capping in tablet formulation.

Purpose: The aim of this study was to prepare formulations of theophylline microbeads usingpregelatinized breadfruit starch (Artocarpus altilis, family Moraceae) in combination withsodium alginate and chitosan at various polymer: drug ratios. Microbead formulations forcontrolled delivery of theophylline would be better alternatives to conventional dosage formsfor optimized drug therapy.Methods: The native and pregelatinized starches were characterized for morphology (scanningelectron microscope), crystallinity (Fourier transform intra-red spectroscopy, FTIR and X-raydiffractometer, XRD), thermal flow (differential scanning colorimeter), density and flowproperties. Theophylline microbeads were prepared by ionic gelation and characterized usingsize, swelling index, entrapment efficiency and time required for 15% and 50% drug release (t15and t50 respectively).Results: FTIR and XRD spectra revealed the orderly arrangement of granules of the semi-crystallinebreadfruit starch was disrupted on gelatinization. The viscosity and flow of pregelatinized starchwere enhanced. Theophylline microbeads were near spherical in shape with size range 1.09± 0.672 to 1.58 ± 0.54 mm. FTIR and XRD spectra confirmed there was no drug-polymerinteraction. Microsphere size, swelling increased while entrapment and dissolution time (t50)reduced with polymer: drug ratio. The entrapment efficiency ranged from 30.99 ± 1.32 to 78.50± 2.37%. Optimized formulation, starch: alginate ratio 3:1 at polymer: drug ratio of 2:1, gave aprolonged dissolution time (t50 = 8.40 ± 1.20 h).Conclusion: Breadfruit starch was suitable as a copolymer for the controlled delivery oftheophylline in microbeads which could serve as a substitute to synthetic polymers in drugdelivery.

Chinese yam (Dioscorea oppositifolia) starch modified by acid hydrolysis was characterized and compared with native starch as a binder in chloroquine phosphate tablet formulations. The physicochemical and compressional properties (using density measurements and the Heckel and Kawakita equations) of modified Chinese yam starch were determined, and its quantitative effects as a binder on the mechanical and release properties of chloroquine phosphate were analyzed using a 2³ full factorial design. The nature (X1), concentration of starch (X2) and packing fraction (X3) were taken as independent variables and the crushing strength-friability ratio (CSFR), disintegration time (DT) and dissolution time (t80) as dependent variables. Acid-modified Chinese yam starch showed a marked reduction (p<0.05) in amylose content and viscosity but increased swelling and water-binding properties. The modified starch had a faster onset and greater amount of plastic flow. Changing the binder from native to acid-modified form led to significant increases (p<0.05) in CSFR and DT but a decrease in t80. An increase in binder concentration and packing fraction gave similar results for CSFR and DT only. These results suggest that acid-modified Chinese yam starches may be useful as tablet binders when high bond strength and fast dissolution are required.