Evaluation of Grewia polysaccharide gum as a suspending agent

Grewia polysaccharide gum was extracted from the inner stem bark of Grewia mollis, thereupon drying was achieved by air-drying (ADGG) or freeze-drying (FDGG). The suspending ability of grewia gum was compared to that of xanthan (XAN), sodium carboxymethylcellulose (SCMC) and acacia gum (ACA) in ibuprofen suspension. The physical stability of the ibuprofen suspension formulations, containing the suspending agents at a range of concentrations, was assessed by appearance and pourability, viscosity and rheology, sedimentation volume ratio, redispersibility, degree of flocculation, zeta potential and microbial load. The ADGG and FDGG-containing formulations exhibited pseudoplastic flow with a viscosity-imparting ability superior to ACA and SCMC-containing formulations, but not XAN, at all concentrations. ADGG-containing formulations (1.0%w/v) remained fully suspended for over 42 days while all the other formulations sedimented within 24 hours except XAN-containing formulations. The FDGG and ADGG-containing formulations were more easily redispersed than SCMC-containing formulations and exhibited a higher degree of flocculation at 0.75%w/v than ACA or SCMC-containing formulations. The zeta potential of XAN, ADGG or FDGG-containing suspension formulations were more negative than-30 mV and therefore more stable than SCMC or ACA-containing suspension formulations (zeta potentials of <-23 mV). All suspension formulations showed evidence of microbial growth on storage. ADGG or FDGG may provide a suitable alternative as suspending agent in pharmaceutical oral suspensions.