Physicochemical Characterization of Gum Isolated from Sterculia setigera for Potential Application as Pharmaceutical Excipient in Tablet Formulations

Sterculia setigera gum, also known as gum karaya, is a vegetable gum produced as an exudate. No teratogenic and mutagenic effects  were reported from gum karaya toxicity studies. The aim of this study was to extract the gum fraction of S. setigera and to characterize its  properties for potential application in pharmaceutical formulations. The colour of the extracted powder was grayish white, and its loss  on drying was 1.2 ± 0.7%, which showed its suitability for formulating stable tablets, especially for moisture-sensitive drugs. The total ash value of S. setigera gum was 6.98 ± 0.41%, which was within the British Pharmacopeia specification. The solubility determination of S.  setigera gum showed that it was sparingly soluble in water and insoluble in organic solvents, but soluble in 1:1 hydroalcoholic mixtures of  ethanol and water or methanol and water. The swelling ratio was high, which increases with temperature. Scanning electron  microscope images showed irregularly shaped (near to triangular), non-spherical, and of varying sized particles. Moisture sorption  increased with increased relative humidity (RH) ranging from 0.40 ± 0.32% at 20% RH to 3.13 ± 0.24% at 100% RH. The Carr’s Index (25.00  ± 0.65) and Hausner Ratio (1.33 ± 0.14) values showed passable flow properties of the gum powder. The DSC and X-ray diffraction studies  showed the amorphous nature of the gum. The findings of this study showed that S. setigera gum’s physicochemical properties were within pharmacopoeial specifications and showed its potential applications as a pharmaceutical excipient such as a binder or a sustained  release excipient in tablet formulations.