Chemical characterization and antioxidant of polysaccharide extracted from Dioscorea bulbifera

Abstract

The air yam (Dioscorea bulbifera) is an unconventional vegetable that produces a reserve stem, which has polysaccharides in its composition. These biopolymers, in turn, have aroused industrial interest due to many of their properties and applications in several areas, such as agro-food, chemical, pharmaceutical, textile, metallurgical, oil, among others. The objective of this work is to characterize the polysaccharide present in the raw and pre-purified air yams, as well as to verify its potential antioxidant capacity. The FTIR analysis showed in the two samples, a characteristic OH band at approximately 3250 cm−1, which is characteristic of polysaccharides. Through the SEM it was possible to analyze the morphology of the samples and verify that they are composed of films or “sheets” without measurable format. Furthermore, by XRD the samples were found to be an amorphous material, with peaks of crystallinity being observed at approximately 21.54° and 23.62° 2θ. Thermal analysis indicates that the NDP sample presents three regions of mass loss, the first one running up to 100 °C and may be associated with water loss; the second occurs from 150 °C, and occurs in several steps that can be visualized by DTG, and the third from 550 °C. The organic matter present in the sample was about 84%. The DP (Dialysed Polysaccharide) sample, in turn, also presented three regions of mass loss, the first one occurring up to 150 °C, the second from 175 °C and the third, from 425 °C. All these mass losses occur in only one stage. The organic matter present in the sample was approximately 80%. The samples presented potential antioxidant activity when analyzed by DPPH, ABTS, FRAP, OH radical removal, H2O2 removal and reducing power. The obtained results are very important, as they reveal information about the chemical characteristics and potential bioactivity of the dialysed and non-dialysed polysaccharide of D. bulbifera.