A study on the factors affecting the compressibility of green tea leaves powder to make a herbal tablet

Evaluation of the role of solvent and the effective factors in the compressibility of the extract powder of green tea leaves to produce a herbal tablet was the main aim of the present study. Green tea leaves were extracted by different solvents of ethanol, methanol, acetone, isopropyl alcohol and de-ionized water, separately in the proportion of 1:4 powder to solvent. The prepared extracts were dried by a freeze dryer. The presence of tannin and its assay was approved by Folin-Denis reaction. The extracted powder of each solvent was divided in to different sizes of 14,18, 35 and 60 mesh by the USP standard sieves and then the flow properties such as repose angle, compressibility percent and also the type of deformation of particles during compression force, were studied. Carr's index was calculated for determination of compressibility percent and Heckel’s plot drawn to distinguish the plasticity or elasticity nature of green tea powder. The most of tannin percent was obtained by the water solvent. The best compressibility percent with Carr’s index 12, was from the powder extracted by water, with 3% constant humidity and 60 mesh particle size. This powder with least of repose angle (250) showed the best flowability. The result of drawn Heckel's plot for this powder indicated a plastic deformation during compression with 95% confidence. It seems that the powder of green tea extracted with the water solvent shows a better extraction of active ingredient from green tea leaves, as compared with alcoholic solvents, and also, a more favorable compressibility with a plastic deformation to the compression force.