Extraction and physicochemical characterization of a potential multifunctional pharma-excipient from crab shell wastes

Abstract

An efficient and beneficial waste disposal mechanism is highly desired. This study was carried out to extract and characterize a potential multifunctional pharmaceutical excipient from crab shell wastes. Shells of  Pachygrapsus mamoratus were obtained from Oron, a coastal town in Akwa Ibom State of Nigeria. Chitin was extracted from the powdered shell by deproteination and demineralization; and chitosan was derived by  alkaline deacetylation of the chitin. The polymer was subjected to Fourier transform infrared (FTIR)  spectroscopy and differential scanning calorimetry (DSC). It was also evaluated for flow properties, pH and  hydration and swelling characteristics. The shells gave a yield of 17% chitosan. FTIR analysis of the polymer showed C-H bond of substituted cyclic hydrocarbon, cyclic C-N bond, C-O bond of glucose molecules, C-H bond of side chain –CH2OH, presence of β-ester linkage, N-H of amides and bonded and free O-H groups. The last  transition in the thermogram of chitosan was a polymer degradation exotherm with a peak at 337.9°C. The  chitosan had higher bulk density, higher flow rate, lower Carr’s index and lower Hausner’s ratio compared to sodium carboxymethylcellulose. It also had lower hydration and swelling capacities. Therefore, the crab shell-derived chitosan has better thermal stability, better flow properties but poorer swelling properties compared to sodium carboxymethylcelluose.

Key words: Crab shell, chitosan, physicochemical characteristics, pharmaceutical excipient.