Bioactive polysaccharides

The isolation and purification of sufficient amoimts of pure bioactive polysaccharides in a reproducible manner was difficult due to the lack of isolation and purification methods. 

As mentioned in the introduction, various reviews over the last ten years show that many plants contain bioactive polysaccharides. Most of the plants studied were chosen due to their traditional use for different kinds of illnesses where the immune system could be involved. The following section will describe the pectic type polymers from the plants most studied for their structure, and activities related to the structure where possible. 

The first paper on the bioactive polysaccharides from Glycyrrhiza uralensis roots was published in 1996 by Kiyohara et al. [57]. They isolated a pectic type polymer with anti-complementary and mitogenic activity that was an acidic pectin, possibly containing rhamnogalacturonan type I as part of the total structure. Degradation of the uronic acid part of the molecule decreased both types of bio activities. The neutral oligosaccharide chains were shown to retain some of the activities of the native polymer, but it was suggested that they should be attached to the acidic core to retain maximum activity. 

In a more recent study it was shown that the roots from G. uralensis, after isolation, fractionation and purification, contain two bioactive polysaccharides of the pectin family termed GU-3IIa-2 and 3IIb-l. 

Yamadas group [85,86] has also taken a Japanese Kampo medicine consisting of many different plants as a starting point for identifying bioactive plant polysaccharides. They foimd in the Kampo medicine Juzen-Taiho-To, composed of many plants, several bioactive polysaccharides with effects in different test systems that may influence the immune system. A study like this can lead to the identification of the best possible source of the plants in the mixture that contain bioactive polysaccharides. 

Starting from bioactive proteins, peptides with similar activity or binding properties could frequently be identified the development of peptide mimetks from those peptides is a classical exercise in medicinal chemistry. The analogous approach for carbohydrates, the development of carbohydrate mimetks from bioactive polysaccharides, is in its infancy. 

An example of the use of carbohydrate-based affinity chromatography is, thus, the separation of proteins which are responsible for the action of bioactive polysaccharides or oses. The strategy consists in the immobilization of these carbohydrates on classical low- or high-pressure affinity phases. We will distinguish two types of ligands those based on osidic structures and those prepared from glycosaminoglycans or polysaccharides. 

The other bioactive polysaccharide that seemed interesting to be used to produce surface-modified nanoparticles reducing their recognition by the host defense was heparin. Heparin is used as a drug for its anticoagulation properties. Additionally, it is an inhibitor of the complement activation phenomenon [116-118]. It was demonstrated that heparin-coated nanoparticles did not activate the complement system [19, 31, 32] and remained in the blood stream for a longer time compared with nanoparticles, which do not show heparin on the nanoparticle surface [89], Other polysaccharides extracted from mushrooms were found to inhibit the activation process of the complement. They could be alternative polysaccharides to produce nanoparticles with a reduced capacity to activate the complement, such as heparin [119],... 

The polysaccharide contents of seaweeds vary according to the species. Generally, these polysaccharides have been extracted using water or aqueous organic solvents (Albuquerque et ah, 2004). However, as the cell wall consists of complex polymers, it is not easy to extract active polysaccharides using solvent extraction process. The production of different bioactive polysaccharides with lyases is required in order to increase the extraction efficiency of more functional ingredients from seaweeds. Therefore, enzyme-assisted extraction technique can be employed as an alternative method to improve the extraction efficiency of bioactive polysaccharides for industrial use (Athukorala et ah, 2009 Kang et ah, 2011). 

Yang, L. and Zhang, L. M. (2009). Chemical structure and chain conformational characterization of some bioactive polysaccharides isolated from natural sources. Carbohydr. Polym. 76, 349-361. 

Moreover, a variety of potential bioactive polysaccharides are also isolated from brown algae where some of them exhibit anti-HTV activity with different mechanism of action. Sulfated polymannurogluronate... 

Large quantities of polysaccharides are available in nature and many of them display a variety of biological functions [1 ]. There is an abundance of literature on the isolation of bioactive polysaccharides from botanical sources [1-5]. This area of research has attracted a lot of interest due to the fact that most of the bioactive polysaccharides are nontoxic with minimal side effects [4,5]. Hence, this class of biopolymers forms ideal candidates for therapeutic applications. Some of the notable bioactivities of botanical polysaccharides include antioxidant, immunomodulatory, and antitumor properties [4-10]. However, the mechanism of action of these biopolymers is not well understood. In general, one of the primary mechanisms of action of polysaccharides is nonspecific immunomodulation [8]. The key mechanism behind the immunomodulatory, anticancer, antibacterial, and other pharmacological activities of plant polysaccharides is to activate macrophages, which then leads to modulation of the complement system that activates the cells involved in innate immunity and improves host defense [1—4,11,12]. 

Solution NMR techniques have been extensively used in the literature for the determination of precise structures of bioactive polysaccharides [90,129,131]. However, it should be noted that the technique is applicable only if the polysaccharides are soluble in a suitable solvent. Nonsoluble polysaccharides can be analyzed using solid state NMR techniques [134]. Normally, magic-angle spinning experiments with cross-polarizaticHi from proton to nuclei are employed in high-resolution solid-state NMR to enable the structural analysis of insoluble polysaccharides. 

As discussed in the previous sections, there is an abundance of literature on anticancer and immunomodulatory activities of polysaccharides isolated from medicinal plants and mushrooms. Some of the bioactive polysaccharides that have been identified in the recent years are summarized in Table 2 along with... 

Srivastava, R. and D. K. Kulshreshtha, Bioactive polysaccharides from plants. Phytochemistry, 28, 2877-2883 (1989). 

Table 9.1 TCM and Kampo herbs containing bioactive polysaccharides...

Source Based on a table in R. Chang 2002, Bioactive polysaccharides from traditional Chinese medicine herbs as anticancer adjuvants , Journal of Alternative and Complementary Therapies 8 561. 

Wang Y, Hong Q, Chen Y, LianX,Xiong Y. Snrface properties of polynrethanes modified by bioactive polysaccharide-based polyelectrolyte multilayers. Colloids Surf B Biointerfaces lOUAdOJl-S3. http //dx.doi.Org/10.1016/j.colsurfb.2012.05.030. 

Kraus S, Wagner H, Liptak A (1996) Labelling of bioactive polysaccharides for resorption studies. Abstract of the 2nd International Congress on Phytomedicine, Munich... 

Bioactive Polysaccharides of Vegetable and Microbial Origins An Overview... 

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