Grewia gum as a potential aqueous film coating agent

The study was aimed at gaining insight into the functionality of grewia gum as a potential aqueous film coating agent in pharmaceutical formulations. Cast free films of grewia gum samples were evaluated for some mechanical properties and the effect of storage conditions to gain insight into the functionality of grewia gum as a fi lm former when applied on solid substrates. Aqueous cast free fi lms of grewia gum samples were prepared with glycerin, propylene glycol or triethylcitrate at 0.75–10 %w/v as the plasticizer. The Young’s Modulus, % elongation and force at break were investigated as well as the effect of storage at 11, 40, 75 and 85 % RH on the integrity of the fi lms. Glycerin had optimum plasticizer effect at 1.5 %w/w and higher concentrations resulted in shiny and smooth fi lms that were unstable on storage at ambient conditions beyond two months. Free fi lms prepared from grewia sample coded-GR exhibited the highest load at failure, being 15.42 ± 3.59 N while tragacanth fi lms were the lowest, 0.22 ± 0.07 N. The fi lms elongation varied from 0.29 ± 0.09 to 20.59 ± 3.65 mm. The Young’s modulus of tragacanth and grewia gum free fi lms were respectively 4.5 ± 1.10 and 4.34 ± 2.97 while HPMC K4M and HPMC E5 had 4–20 times higher values. Cast free fi lms with propylene glycol were soft and tender and triethylcitrate was not compatible as a plasticizer in the formulations. Selection of a compatible plasticizer and concentration are important in the integrity of cast fi lms of grewia gum.