Intrinsic and Functional Properties of a Gelling Gum from Dioclea reflexa: A Potential Pharmaceutical Excipient

Abstract

Aims: Dioclea reflexa Hook F., is a woody vine widely distributed within tropical Africa and South America, in Nigeria flour prepared from the seeds is used as a soup thickener. The objectives of this study were to extract and modify the native gum from the seeds of D. reflexa, and evaluate their physicochemical and functional properties as a potential pharmaceutical excipient. Place and Duration of Study: Department of Pharmaceutical Technology and Raw Materials Development, National Institute for Pharmaceutical Research and Development, Abuja, Nigeria. Between January 2009 and October 2010. And Department of Pharmaceutics, Faculty of Pharmaceutical Sciences, University of Nigeria, Nsukka, Nigeria. Between June 2010 and October 2011. Methodology: Native D. reflexa gum (DR-gum) was extracted from the seeds of D. reflexa and modified by ionotropic gelation in calcium chloride solution. The gum’s gel clarity and swelling in buffer solutions of different pH (4, 7, and 9.2), as well as the moisture sorption characteristics at different relative humidity (RH) were determined in relation to guar gum (G-gum). Also, the Fourier transform infrared (FT-IR) and Differential scanning calorimetry (DSC) analysis as well as the powders’ flow properties were evaluated. Results: DR-gum, XDR-gum and G-gum are typical hydrogels showing considerable responsiveness in swelling and gel clarity to changes in pH. The DSC thermographs of DR-gum and G-gum were similarly characterized by a glass transition and a cold crystallization transitions peaks as compared to the glass transition and melting transition peak of XDR-gum. The moisture sorption profile indicated that DR-gum and G-gum are moderately hygroscopic while XDR-gum is slightly hydroscopic. The FT-IR of the gums showed the basic differences in the functional groups of the respective polymer chain network. The bulk particles of the three gums showed comparative good flow. Conclusion: The basic similarities and differences in the physicochemical and functional properties of DR-gum and XDR-gum, and G-gum indicate their potential as a pharmaceutical excipient.