The complex world of polysaccharides edited by Desiree Nedra Karunaratne

 

The Complex World of Polysaccharides 

604 

A natural substance that helps in these anti-obesity treatments that has been highly 

recommended to control obesity is chitosan (Hennen, 2005). Chemically speaking, chitosan 

(Figure 1) is a linear polysaccharide of 1→4)-linked-2-amino-2-deoxy-D-glucopyranose 

obtained by deacetylation of chitin, the main component of the exoskeleton of insects and 

crustaceans (Kumirska et al., 2010). It has many important properties, such as non-toxicity, 

biocompatibility, biodegradability, antimicrobial activity, chemical reactivity (Cummings et 

al., 2010), industrial applications (Hennen, 2005), as well as carrier for body fat (Ni Mhurchu 

et al., 2004; Ni Mhurchu et al., 2005; Jull et al., 2008; Lois & Kumar, 2008), cholesterol and 

triglyceride (Razdan & Petterson, 1994; Liu et al., 2008; Zhang et al., 2008). Many 

mechanisms (Tapola et al., 2008; Prajapati, 2009) to explain the carriers and absorptive 

properties of microenvironment produced by chitosan in solution have been proposed. 

However, the use of chitosan is still controversial, and studies in favor and against the use of 

chitosan have been constantly reported. Many studies have confirmed the 

hypocholesterolemic activity of chitosan (Sugano et al., 1978; Liao et al., 2007; Yao et al., 

2008; Liu et al., 2008; Zhang et al., 2008). The same way, works have reported that the 

triglyceride and cholesterol absorption have been inhibited and the cholesterol 

concentration of mice fed with a high fat diet plus chitosan has been decreased (Razdan & 

Petterson, 1994; Liu et al., 2008; Zhang et al., 2008). Other studies reported that chitosan is 

efficacious in facilitating the reducing body fat and weight loss in obese individuals (Schiller 

et al., 2001; Kaats et al., 2006). 

On the other hand, studies have shown that oral administration of chitosan has weak action 

on the reduction of triglyceride and plasma cholesterol in rabbits (Hirano & Akiyama, 1995). 

Other works have reported that the effect of chitosan on body weight is minimal and 

unlikely to be of clinical significance (Ni Mhurchu et al., 2004; Ni Mhurchu et al., 2005; Lois 

& Kumar, 2008, Jull et al., 2008), as well as that the fat trapped was clinically insignificant in 

studies with overweight adults treated with chitosan capsules before each meal (Pittler et al., 

1999; Pittler & Ernst, 2004; Gades & Stern, 2005).  

 

Figure 1.

 Chemical structure of chitosan. 

Is well known that chitosan produces microenvironments with carriers and absorptive 

properties in acidic aqueous solution. These begin to form above a certain concentration, 

critical aggregate concentration, CAC (Rodrigues, 2005). The mechanism of solubilization of 

molecules is well known (Rodrigues, 2005; Rodrigues et al., 2008) however, the process by 

which chitosan acts as a carrier of fat is not yet fully understood and two mechanisms have 

been suggested (Prajapati, 2009; Tapola et al., 2008). One of these mechanisms describe the 

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The Chitosan as Dietary Fiber: An in vitro Comparative  

Study of Interactions with Drug and Nutritional Substances  605 

effect of chitosan fiber network, were chitosan also binds neutral lipids like cholesterol and 

triglycerides through hydrophobic bonds (Tapola et al., 2008; Prajapati, 2009). In other 

mechanism, the positive charges (NH

3+

 group generated by stomach acids) on chitosan 

attract and binds to fatty and bile acids (both negatively charged). This complex is 

indigestible by the body and excreted in the feces (Tapola et al., 2008; Prajapati, 2009). 

Regardless of the solubilization mechanism, nutrients can also be solubilized in chitosan 

microenvironments, as reported in some studies. Works demonstrated that chitosan causes 

significant decrease in protein digestibility (Deuchi et al., 1994) and its effect on nutrient 

digestibility (Ho et al. 2001). Nevertheless, studies on the interaction of chitosan with 

nutrients are still rare and inconclusive (Gades & Stern, 2005; Hennen, 2005; Kaats et al., 

2006; Barbosa et al., 2007; Tapola et al., 2008). 

In this context, we present a comparative study of interactions of the chitosan with 

molecules of two vitamins and one drug. To each molecule, the study was conducted in acid 

aqueous solution, condition similar to the stomach environment, where occurs formation of 

chitosan gel responsible for solubilizing molecules. 

Drug fluoxetine was chosen for this study. The need for anti-depressive drugs with few side 

effects, as anticholinergic activity and cardiovascular accidents, boosted the development of 

new anti-depressant compounds (Böer et al., 2010), as fluoxetine, which inhibits the uptake 

of serotonin by the neurons in the brain, enhances serotonin neurotransmission and had the 

longest half-life that other selective serotonine reuptake inhibitors (SSRIs) (Rizo et al., 2011). 

The precise mechanism of action is not clear but it has less cardiovascular, sedative and 

anticholinergic effects than the tricyclic antidepressant drugs (Shah et al., 2008). The main 

indications for the prescription of fluoxetine are for obsessive-compulsive disorder, 

depression therapy, bulimia nervosa, alimentary disorders and obesity (Suarez et al., 2009). 

Besides drug, the nutritional reeducation and intake of dietary fibers as chitosan has been 

recommended in treatments for obesity (Aslander-van Vliet et al., 2007). Based on the 

possible concurrent use of fluoxetine and chitosan, it is important to evaluate the 

interactions between both substances. 

Vitamins chosen for this study were the B2 and B12. Vitamin B2 or riboflavin is a vitamin B 

complex that participates in numerous metabolic reactions and physiological functions 

(United States Pharmacopeia, 2007). Vitamin B12 or cyanocobalamin is an essential 

component in human diet, plays a key role in cell nucleus, enzymatic processes in the 

mitochondria, and cytoplasm; it is necessary for the synthesis of red blood cells, for the 

maintenance of the nervous system, and for the growth and development in children (Wang 

et al., 2007). Both vitamins are not produced by the body and are consumed only in small 

quantities (Sommer, 2008); deficiency can cause many diseases (Sun et al., 2007). 

The interactions between chitosan-vitamin and chitosan-drug have been verified by 

monitoring the photophysical properties of these components. For this, fluorescence and 

UV-Vis absorption measurements were initially evaluated in acid aqueous solution and 

after in weakly acidic solution of chitosan given information about the interactions between 

this chemical component in conditions that approaches the stomach chemical environment.  

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