Extraction and Physicochemical Characterization of <i>Adansonia digitata L.</i> Mucilage

Abstract

Background: Adansonia digitata leaves are edible and they contain a significant amount of mucilage that has shown potentials for  pharmaceutical application. However, there is paucity of information on this mucilage contained in its leaves.

Objective: This study aimed to determine a suitable method for extraction of Adansonia digitata mucilage (ADM) as well as to characterize its physicochemical properties.

Materials and Methods: ADM was extracted from the aqueous dispersion of the dried leaves powder of Adansonia digitata L. in water via  precipitation with ethanol. Physicochemical characterization of ADM was based on viscosity, chemical composition, particle size  characterization via QICPIC, Scanning Electron Microscopy (SEM), Attenuated Total Reflectance Fourier Transforms Infrared (ATR -FTIR)  spectroscopy, Nuclear magnetic resonance (NMR), moisture content and Dynamic vapor sorption (DVS) studies as well as pH and  aqueous solubility tests. In addition to this, colour of the mucilage and thermal analysis via DSC were used as criteria for selection of the  most suitable method for extraction of ADM.

Results: Colour and thermal analysis revealed a level of purity in the extraction process. The irregular needle like structures of ADM  revealed by SEM was found to be mildly acidic with a high viscosity that is concentration dependent in aqueous medium. Thermal  characterization revealed a glass transition (Tg) and melting temperatures (Tm) of 55.61 °C and 179.10 °C respectively. Finger prints of  functional groups revealed azo aromatic groups and other chemical constituents of sugars including glucose, galactose, arabinose and  rhamnose, and sugar acid form of galacturonic acid were identified by NMR. Moisture sorption provided insight into water sorption  mechanism, processing, packaging and storage conditions of the mucilage.

Conclusion: Extraction of ADM via a heat free method  improved its colour and purity based on the technique used. The mucilage was found to be a highly viscous and hydrates rapidly with  good gelling properties. In addition its moisture sorption characteristics and glass transition temperature gave insight into its stability,  storage and packaging conditions. These properties reveal its potential for many pharmaceutical applications including binding, coating,  gelling agents as well as matrix forming.