Читать книгу Polysaccharides - Группа авторов - Страница 27

A large variety of different methods of obtaining A. vera gel involving more than one step was found. Products derived from A. vera gel are commercially available in the form of gels, liquids, and particularly in spray dried or freeze dried products extracted from the inner part of the leaf, followed by stages of separation of insoluble fibers, alcohol precipitation of polysaccharides and purification of acemannan. Several authors have analyzed the composition of free sugars and used techniques for separation and purification of polysaccharides from A. vera gel and have determined the constitution of the monomers present. However, the types and molecular sizes of the polysaccharides isolated from A. vera gel vary due to factors such as the plant subspecies or seasonal differences in cultivation, different techniques used to isolate the polysaccharide, polysaccharide degradation during processing and also the analytical methodology applied.

These differences hamper standardization of the process of obtaining A. vera gel and of an analytic methodology for quantifying its principal polysaccharide, acemannan, yielding non-reproducible data. However, based on the studies reviewed, natural polysaccharides are not stable under conditions of stress, such as the application of heat or enzymatic processes, leading to degradation of acemannan and loss of physical and biological properties of A. vera. Thus, the method by which the plant is processed can lead to final preparations with different chemical compositions. Therefore, selecting the right process to ensure the desired chemical composition of the end product is vital, thereby retaining the high molecular weight polysaccharides present in the fresh gel.

Given that the inner gel obtained from A. vera is considered a source of biological activity attributed to the plant, it is essential to apply the body of knowledge on the chemical composition of A. vera to inform future studies for product standardization and development, and also to establish the most suitable method (or combination of methods) for quality control and subsequent confirmation of pharmacologic activity.