Preparation and Characterization of Cellulose and Microcrystalline Cellulose from Sugarcane Bagasse and Assessment of the Microcrystalline Cellulose as a Directly Compressible Excipient

Abstract

Cellulose, the most abundant biomass material in nature finds wide applications in the pharmaceutical industry. Sugarcane bagasse (SCB)  is one of the main agricultural lignocellulose byproducts. The objective of this study was to prepare and characterize native and  microcrystalline cellulose (MCC) from SCB and evaluate the MCC as a directly compressible pharmaceutical excipient. Cellulose was  extracted from SCB by chlorine-free methods with or without dewaxing. MCC was prepared from the cellulose by hydrolysis using  hydrochloric acid, and subsequently oven-dried (OD) or spray-dried (SD). The as-obtained cellulose and MCC were characterized in terms of yield, degree of polymerization (DP), chemical functionality, crystallinity, morphology and thermal stability. The chemical composition,  particle size, densities and direct compressibility of MCCs were also determined. Cellulose yields on a dry weight basis were found to be  42.8 ± 1.10% and 43.5 ± 0.5% from non-dewaxed and dewaxed SCB, respectively. Dewaxed SCB cellulose (DSCBC) provided higher yield of MCC (DSCB-MCCOD, 83 ± 0.74%) than non-dewaxed SCB cellulose (SCBC) (SCB-MCCOD; 78 ± 1.07%). The DP of SCBC and DSCBC were  580.56 and 592.75, respectively, while the DP of MCC ranged from 230.10 - 251.40. The FTIR spectra of both cellulose and MCC were similar with that of Avicel PH-101. The degree of crystallinity of the dewaxed cellulose (77.34%) and MCCOD (79.56%) and MCC-SD (81.87%) were  higher than non-dewaxed cellulose (74.50%) and MCC-OD (78.11%) and MCC-SD (79.62%). Scanning electron micrographs (SEM) showed a  fibrous structure for DSCBC and rod-shaped for DSCB-MCC. Thermogravimetric analysis (TGA) revealed dewaxed products exhibited better thermal stability than non-dewaxed products. All MCC samples exhibited monomodal normal particle size distributions. The Hausner ratio and Carr’s index of DSCB-MCCOD and Avicel PH-101 were not significantly different (p < 0.05) indicating similar flow property and  compressibility of the materials, respectively. Also, plain tablets prepared from SCB-MCC showed reasonably high crushing strengths (MCC-SD > MCC-OD), although tablets of Avicel PH-101 showed the highest crushing strengths. Thus, SCB could be an alternative source of cellulose and MCC for pharmaceutical applications.