Spectroscopic characterization (Raman and infrared) of Aloe maculata from the north Argentina region

Abstract

In this work we present the Fourier-transform infrared (FTIR) and Raman spectra of Aloe maculata (A.maculata)(“maculata” = with spots) gel after elimination of the aloin fraction. The analyzed samples were harvested from two zones of different heights in northern Argentina. From the FTIR measurements it was possible to identify the presence of pectin in the gel, where an analysis of the degree of esterification was done on the basis of characteristic marker bands for the different aloe samples. The effect of the storage time of both samples was also monitored revealing that the degree of esterification undergoes a decrease upon the storage time in all samples. By this way, it was determined that the samples of A. maculata collected from the high lands, present a higher esterification degree in pectins than those collected from the low lands. In order to better follow the distribution of the different spectral signals, we performed a Raman mapping in a selected area. The Raman measurements helped to determine the characteristics of the different fibers of the Aloe gel. Furthermore, theoretical calculations carried out on a molecular model of one important aloe gel component, the acemannan, aided in the assignment of the modes of the groups present in the gel samples. This investigation is important in order to assess the influence of the harvesting place and the storage time on the use and commercialization of the aloe products, since a higher degree of esterification gives rise to a higher viscosity and, consequently, a better bioavailability.