The material and tablet formation properties of starches from four different Dioscorea species, namely White (D. rotundata), Bitter (D. dumetorum), Chinese (D. oppositifolia) and Water yam (D. alata), was characterized to determine their applicability as direct compression excipient. The physicochemical, thermal, morphological and material properties of the starches were investigated. The tablet formation properties were assessed using the 3‐D modeling parameters, the Heckel equation and the force‐displacement profiles. The tablet properties were evaluated using the elastic recovery and compactibility plots. The results indicate that the chemical composition, thermal and material properties of the starches varied considerably among the four species. The sorption isotherms show that the relative humidity (RH) during tablet production and storage should be carefully controlled. The tableting results show that all four starches exhibit similar time dependent deformation (d). The ranking for pressure plasticity (e) was Water > Chinese > White > Bitter, which indicates that Water deforms more easily and Bitter less easily. The ranking for fast elastic decompression was White > Water ≥ Chinese > Bitter. The amylose content, size and shape of the starch granules and specific surface area appears to play a significant role in the compressibility. Thus, White and Water with larger granules and high amylose content exhibited poor compressibility and did not form compacts except at high ρrel,max, while Bitter and Chinese with polygonal shape, small particle size and high specific surface area were more compressible and formed tablets of acceptable crushing force. Thus, Chinese and Bitter could be useful as excipient in direct compression.

The aim of the study was to analyze hydroxypropylcellulose (HPC) in pure form and in excipient mixtures and to relate its physical and chemical properties to tablet binder functionality. The materials used were Klucel hydroxypropylcellulose grades ranging from low to high molecular weight (80-1000 kDa) of regular particle size (250 μm mean size) and fine particle size (80 μm mean size). These were compared with microcrystalline cellulose, spray-dried lactose, and dicalcium phosphate dihydrate. Thermal behavior of HPC was analyzed by modulated temperature differential scanning calorimetry (MTDSC). Tablets of the pure materials and of dry blends with 4% low viscosity, fine particle HPC and 30% high viscosity, fine particle HPC were produced on an instrumented eccentric tableting machine at 3 relative humidities. The 3-dimensional (3-D) model with the parameters time plasticity d, pressure plasticity e, and the twisting angle ω, the inverse of fast elastic decompression was compared with the Heckel method for characterization of compaction. Elastic recovery and compactibility were also studied. The results show that HPC tablet formation is characterized by high plastic deformation. The d, e, and ω values were markedly higher as compared with the reference materials. Plasticity was highest for the fine particle size HPC types. Maximum compactibility was observed for low molecular weight, fine particle size HPC. Tableting of the mixtures showed deformation, which was strongly influenced by HPC. Plasticity and crushing force of formed tablets was increased. In conclusion, HPC is characterized by strong plastic deformation properties, which are molecular weight and particle size dependent.

Starches obtained from four different Dioscorea species namely White (D. rotundata), Bitter (D. dumetorum), Chinese (D. oppositifolia) and Water yam (D. alata), were modified by acid hydrolysis and the physicochemical, material and tablet formation properties of the starches were investigated with the aim of determining their usefulness as a direct compression excipient in pharmaceutical tablets. The results obtained indicate that the physicochemical, material and tablet properties of the acid modified Dioscorea starches varied considerably among the various species. Acid hydrolysis led to an increase in solubility but decrease in swelling of the starches. Acid modification also led to an increase in the compressibility of the starches when compared with the native forms of the starches. Acid modified Water and White formed intact stable tablets only at higher rho(rel,) (max), while acid modified Chinese and Bitter formed tablets at all relative densities which could already be predicted from the deformation behaviour as analyzed by 3-D modeling. The result indicates that acid modified starch tablets showed higher crushing force and acceptable disintegration time and could therefore be useful as directly compressible excipient.

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