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A diet rich in soluble fiber such as pectin results in a decrease in total cholesterol and low-density lipoprotein LDL in the blood without affecting the high-density lipoprotein HDL [ ]. In addition, pectin enhances the excretion of bile acids, a substance that helps to remove the excess of cholesterol on the body, lowering consequently the serum cholesterol levels [ ]. Gunness and Gidley [ ] have proposed three possible mechanisms in order to explain the effect of reduction of total cholesterol and low-density lipoprotein LDL by the consumption of pectin. The first is the inhibition of reabsorption of bile salts within the enterohepatic circulation.
Second, the high viscosity of the pectin could in turn affect the glycemic response, by reducing the rate of glucose absorption. Finally, the selective fermentation of the fiber by the colonic microbial populations prebiotic effect , produces short chain fatty acids, especially propionate which can inhibit the synthesis of cholesterol in the liver. The properties of several types of pectins to reduce cholesterol are related first to their physicochemical properties, including viscosity, molecular weight and degree of esterification [ ]. Pectins have the capacity to form viscous gels that bind cholesterol and bile acids, promoting their excretion and reducing reabsorption.
The cholesterol absorption is further hindered by disruption of micelle formation, constituted by bile salts, phospholipids and fatty acids [ ]. Both high methoxyl and low methoxyl pectins reduce total cholesterol, and they have no effect on high-density lipoproteins HDL which are beneficial to health, but diverse studies have shown that high methoxyl and high molecular weight pectins are more effective in reducing cholesterol than low methoxyl pectins [ ]. Espinal-Ruiz et al. The extent of lipid digestion was diminished with the increase of the molecular weight and pectin methoxylation.
Pectins with higher degree of methoxylation affected the rheological properties of the gastrointestinal fluids, bringing an increase in the hydrophobicity of the molecule and decrease the number of negative groups. These authors suggest that having control of the lipid digestibility in the gastrointestinal tract can act as a functional food in the design of emulsion-based food and thereby promote health. Inhibition o lipid droplet digestion by pectin isolated from banana passion fruit.
Toxic metals as arsenic, cadmium, lead and mercury interrupt the normal functioning of the endocrine, neurological and immune systems, in addition to other functions in the human body. Normally heavy metal poisoning is treated by specific chelators such as ethylenediaminetetraacetic acid EDTA , 2,3-dimercaptosuccinic acid DMSA orsodium 2,3-dimercaptopropanesulfonic acid DMPS , which bind metals in the blood and facilitate their removal via urine and fecal routes. The levels of metals in the body can be reduced but these treatments may trigger secondary effects such as redistribution of metals in the brain or bones, reduction of essential minerals, disturbances in gastrointestinal function and skin rashes [ ].
Pectin has metal- binding capacity, aids in the elimination of heavy metal ions, and is considered a reliable alternative to conventional chelators without secondary effects [ , ]. The ability of pectin to reduce absorption and the bioaccumulation of toxic metals is attributed to pectin binding the metals in the digestive tract and preventing their absorption while facilitating their elimination in the feces.
The chemical structure, physicochemical properties and high heterogeneity of pectin in terms of molecular weight, degree of esterification, dispersion, and uronic acid content may hinder the metal-binding capacity of pectins [ 18 ]. Therefore, molecular tailoring and transformation is needed to render low methoxy pectin more effective [ ].
Kyomugasho et al. In addition, increments in the pectin concentration decreased the mineral-bioaccessibility in the digestive tract. The optimal in vitro bioaccessibility of mineral ions may be achieved controlling the structure of pectin. The effects of modified pectins on the excretion of toxic metals in humans have been studied.
Eliaz et al. These authors infer that the presence of rhamnoglactoturonan II rich in free carboxyl groups in pectin contribute to the chelation of metals. Figure 4 shows the proposed mechanism of action of fiber chains to entrap toxic metals as mercury, lead and cadmium. The positively charged metals are bound to the fiber chains and eliminated from the body [ ].
Why Were Polysaccharides Necessary?
For its part, in a study conducted by Zhao et al. In addition, no side effects were reported on negatively affected health. This study shows the effectiveness of modified citrus pectin as a chelator of lead, for its optimal structure, efficient for the chelation of heavy metals. The mechanism is still a subject of interest for science. The presence of toxic metals like zinc in aqueous solutions derived from industrial waste, also represents a high risk to environmental and human health due to large excess of zinc, may be carcinogenic.
The use of pectin with low degree of esterification close to zero with pH in a range of 4—7 can be very effective for elimination of heavy metals in aqueous disposals acting as sorbents [ ]. Another promising feature of pectin is its apparent synergism and chemoprotective action on metastasis of cancer and the growth of primary tumors in multiple types of cancer in human and animals.
Polysaccharide Dispersions Chemistry And Technology In Food Food Science And Technology
Leclere et al. These mechanisms are still under study and seem to depend on the structure of the pectin to yield various active fragments that can antagonize an active site or bind molecules, which can induce cellular apoptosis and inhibit tumor metastasis [ ]. In the literature there exists a considerable number of reports that provide evidence for a role of pectin and modified pectinin the inhibition of different types of cancer. The list includes prostate cancer [ , ], colon cancer [ , ], pancreatic cancer [ ], breast cancer [ ] and metastasis [ ].
In addition, it has been reported that this polysaccharide has the capacity to reduce cell proliferation, migration, adhesion, and induce apoptosis in a variety of cancer cell lines [ 13 ]. Pectins can be used in the form of dietary fiber and, since pectin is not digested in the gastrointestinal tract, it could protect cells from mutagenic phenomena in at least three ways. First, pectin is fermented in the colon by bacteria, and one of the products generated by this fermentation is butyrate, which inhibits colon inflammation and prevents carcinogenesis; then pectin and mainly modified pectins can interact with galectin-3 to inhibit cell metastasis; and, finally, the induction of apoptosis in cancer cells can be generated [ ].
Modified pectin has shown to be more effective against cancer, when shorter, low branched, water soluble and galactose-rich modified pectin polysaccharide fractions are obtained by pH and temperature treatments. They have the ability to access and interact tightly with galectin-3 Gal3 [ ]. Galectin-3 is a type of lectin protein that is implicated in cancer, immune function and inflammation.
High levels of galectin allow a greater adhesion and agglutination of cancer cells in the site of metastasis. Modified citrus pectin appears to act as a binding agent for the galectin-3 receptor site, binding it together and blocking the ability of cancer cells to bind to another site. This prevents the addition of tumor cells and their subsequent addition to endothelial cells [ ]. Figure 5 shows the different pathways of action of galectin-3 at extra and intracellular levels. Roles of galectin-3 at extracellular and intracellular levels.
At extracellular level Gal3 participates in cell adhesion. The relationship between the structure ofmodified pectin and its inhibitory activity on galectin-3 was investigated in several studies [ , ]. In a model of liver metastases and colon cancer in mice, the level of expression of galectin-3 was higher compared to that of normal mice.
In the study, modified pectin showed an effective inhibition of liver metastasis in a dose-dependence manner and also of the tumor volume of colon cancer in the model [ ]. In this regard, Maxwell et al. The expression of genes involved in the cell adhesion was investigated. Briefly, the structure of pectin has an important role in the regulation of the antiproliferative activity. The RGI-region of pectin decreased the proliferation of carcinogenic cells; also, the expression of the gene ICAM1 decreased significantly in the colon cancer cells treated with RG-I, suggesting that this gene may play a role in the reduction in cell growth.
These findings support the theory that HG segments in RGI, as well as the presence of neutral sugar side chains, are essential for pectin bioactivity. These same authors evaluated in the antiproliferative activity of a pectin extract from sugar beet under alkali treatment in colon cancer cells. The alkali treatment decreased the degree of esterification of pectin, which increased the observed ratio of rhamnogalacturonan I RGI to homogalacturonan. In studies conducted with humans, Guess et al. This was the first published human clinical trial to use MCP to demonstrate it effect on the time of duplication of prostate specific antigen.
In a pilot clinical trial the use of modified citrus pectin in patients with advanced solid tumors was evaluated, in terms of tolerability, clinical benefit and antitumoral efficacy. The results obtained showed a significant improvement of quality of life and stabilization of patients. In addition, no patient developed any severe therapy-related adverse events.
Most of the patients had improvements in their quality of life [ ]. The use of pectin as a matrix for the controlled delivery of drugs has raised interest in recent years mainly in biomedical applications such as drug delivery [ 14 , 18 ], gene delivery [ ], tissue engineering [ , ], wound healing [ ] and wound dressing material [ ], for its capacity to form stable gels and its simple gelling mechanism. For some pectin hydrogels applications to drug delivery, pectin with a high degree of esterification has been used, but variables such as high molecular weight and poor solubility in water, can considerably affect the encapsulateddrugs, leading to drug migration, early release or erosion of the cover.
So in terms of desirable structure of pectin, the utilization of pectin with low degree of esterification is preferable, for its low molecular weight; also amidated pectins with low methoxy can influence in the junction zones [ , ]. Pectin has the ability to form gels in presence of calcium to create a water-insoluble cross-linked polymer called calcium pectinate caP. This material is considered an attractive candidate for colonic drug delivery and forms hydrogel which can encapsulate drug molecules [ 16 , ]. Penhasi et al. On the other hand, caP films with low concentration of sodium chloride presented high biodegradability being highly degraded by enzymes of the colonic bacteria and can be use as delivery system for hydrophobic active material.
As a natural polymer, pectin has interesting properties such as biocompatibility, mucoadhesiveness, safety, inertness, and has the ability to form gels in acid environments; hence, it is considered a suitable candidate for drug delivery models [ 18 ]. The encapsulation of bioactive compounds in biomaterial carriers as pectin has been studied.
The De Souza [ ] group worked with pectin microparticles elaborated by the electroaspersion technique with the aim of using them as a directed release medium where an active compound from mango was encapsulated, mangiferin, a compound of therapeutic interest for its antioxidant, prebiotic, antiviral, antitumor and anti-allergenic properties. For its part, the release of theophylline coated in pectin and calcium pectinate films were evaluated in an in vitro drug release study.
The drug release was successful in an acidic medium pH dependent in a bi-layer film with combination of pectin and calcium pectinate [ ]. Pectin has also been used as a targeted delivery vehicle for cancer; Jantrawut et al. The results obtained indicated, that rutin encapsulated in low methoxyl pectin showed a higher anticancer activity than the non-encapsulated rutin.
This polysaccharide has been studied and used for the specific delivery in nasal, ocular and oral treatments. The mucoadhesive potential of pectin with low degree of esterification may be due to associations by hydrogen bonding between pectin free acid groups and mucin in aqueous medium and thought adsorption mechanism of pectin on the mucin molecule [ ]. Pectin has been proved as nasal spray to improve the analgesic onset, treatment efficacy and acceptability to treat cancer pain, where a rapid drug release is requested [ , , ].
The use of pectin has been evaluated in ocular disorder treatments as a new strategy to enhance contact time and drug penetration in the eye, owing to the fact ophthalmic drugs present certain disadvantages likepoor bioavailability due to the protective mechanisms of the eye [ 17 , ]. In a patent obtained by Ni and Yates [ ], the formation of a pectin gel in situ was evaluated to apply it in liquid form and then gels in the eye. The presence of electrolytes and pH of the tear film conducted to the gelation of pectin. For its part, preliminary studies were assessed on pectin microspheres as an ocular delivery system for piroxicam.
This system, can ensure high bioavailability, also has been shown to reduce some disadvantages of other ophthalmic delivery systems pomades, inserts, liposomes such as vision blurring, need for insertion and removal, and stability problems [ ]. The gastrointestinal tract and its probable distribution in the percentage of colon cancer [ ]. In a study performed by Dev et al. The results obtained showed that this formulation has a latency period of 4 h, enough time for the system to release the drug in the colonic zone.
In this regard, experiments carried out by Jung et al. Also, the hydrogel beads were able to protect drug from the conditions of the simulated gastric environment, being a suitable candidate for a colon targeted drug delivery system. Nevertheless, pectin by itself is not totally effective in all cases to achieve formulations capable to reach the colon in unaltered. Some authors have reported matrix formulations of pectin coated with polymers that protect the pectin complex during its journey through the upper digestive tract.
The interaction of pectin with some food polysaccharides is described in the text below. The interaction between biopolymers has been widely studied for its great scientific importance and for its relevant new applications. For this, it is very important to understand the interactions that happen among different mixtures of polysaccharides, which, can result commercially attractive in the development of formulations with better stability or more desirable textures and above all, obtain a higher cost benefit, decreasing the use of expensive synthetic biopolymers by replacing them with cheaper and safer ones [ ].
There are two essential types of interactions between polysaccharides: 1 attraction between the molecules, that occurs when the polymers are attracted to each other having an energetically favorable association; and 2 repulsion by steric exclusion, where the polymers repeal and exclude each other from the space they occupy [ ]. The combination of different types of biopolymers is in constant growth, and diverse materials have been formed with different polysaccharides as starch, pectin, chitosan, cellulose, among others.
Pectin is a biopolymer that has aroused greater interest in the formation of new composite material for its physicochemical and ionic characteristics [ 8 ]. Some interactions between pectins and other polysaccharides with potential uses in food and pharmaceutical industries are described below. Pectin- alginate systems were the first reported mixed gelsand are widely studied to this day. Diverse authors have reported that the structural properties of this type of mixed gels depends largely on the pectin-to-alginate ratio, the degree of esterification of pectin and the mannuronic and guluronic acid proportions of alginate [ , ].
Toft [ ] reported that mixtures of HM pectins and alginates with high content of l -guluronic acid gels sinergistically under certain conditions in which neither the pectin nor the alginate can form cohesive gels by their own. HM pectins require high solids concentration and low pH for gelling, whereas gels obtained from mixtures of HM pectin-alginate are largely independent of the solids content and also less dependent on pH, representing an advantage [ ]. Also, the presence of alginate enhances the structure development rates during gelation of pectin-alginate-sugar systems [ ].
It is important to mention that alginate with higher guluronic acid content, leads to the formation of gels with higher stability. In pectins with low degree of esterification, a much lower pH is needed to form gels with alginates. One of a few determining factors to explain the synergistic interaction between the galacturonic acid chains of pectin and the guluronic acid blocks of alginate, is the structural similarity between these polymers, being both polyuronates.
In fact, pectins and alginates can undergo intermolecular binding to rise coupled networks [ ]. The interaction between pectin and alginate is enhanced as the proportion of these sequences is increased. The gelation mechanism between pectin and alginate involves intermolecular junction zones formed by the union of polyvalent cations e. Rezvanian et al. The mixture of pectin-alginate can lead the formation of thermoreversible gels making it one of the most interesting features for the food industry, including preparation of cold-setting fruit gels, stabilization of acidic emulsions like salad cream or mayonnaise.
Also, these mixtures can be used in low sugar or calorie jams and jellies [ ]. Other important uses of these polysaccharide mixtures are in the pharmaceutical industry as matrices for the encapsulation of diverse active ingredients [ , ] and as drug delivery systems [ ], mainly as colon-specific drug delivery [ ].
This is due to the fact that pectin and alginate can remain intact in the upper gastrointestinal tract and are degraded by specific enzymes produced by bacteria that inhabit the human colon [ ]. Many examples have been reported in this decade. Hsu et al. As the authors state, the binary mixture enabled the best prolonged release profile of these compounds in simulated gastrointestinal fluids. Galus and lenart [ ] characterized diverse physical properties of composite edible films of pectin and alginate concluding that the combination of both polysaccharides gave continuous, homogenous and transparent films.
Seixasa et al. Many more potential applications are still being assayed for new food products and drug carrier design. Pectin and chitosan are polysaccharides which can form complexes useful for their biodegradability, biocompatibility and non-toxicity. Chemical structure of a polycation chitosan and b RG-I region of polyanion pectin and c electrostatic interactions between pectin-chitosan [ ]. Different interactions can occur between the groups in pectin-chitosan complexes:van der Waals, electrostatic, hydrophobic, hydrogen and coordination bonding. The presence of these polar functional groups results in a very strong intermolecular interaction and highly ordered orientation of the rigid chain polymers [ , ].
The stability ofthese pectin-chitosan complexes depends mainly of the pH, charge density, concentration of both polymers and on the ionic conditions of the medium. In addition, temperature, concentration of certain molecules, among other environmental conditions may play a significant role in this mixed gels stability [ , , ].
There are extensive investigations dedicated to the studies of the physicochemical properties of the interaction between pectin and chitosan [ , , , ]. Rheological investigations have shown that the gelation is thermoreversible when the pH value is below two and that the gelling temperature is dependent on the weight ratio of the polysaccharides [ , ].
Marudova et al. These polyelectrolyte complexes have many uses in diverse fields like food industry [ ], biomedicine [ , ], and pharmaceutical industry, especially as a drug delivery vehicle [ , ] and colon-specific drug delivery [ , , ]; these drug carriers include hydrogel, films, tablets, pellets and beads.
The interest on this system for controlled release of drugs lies in the fact that both polymers have the capacity to protect the drug from being released in the upper intestinal tract and deliver it in the colon [ ]. The complex showed higher resistance to UV action compared to polymers only; UV rays did not affect significantly the morphology and thermal stability of the complexes, which favors applications such as medical or pharmaceutical industry.
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The interactions between pectin and protein can occur through two different mechanisms in nature: associative phase and segregate phase separations, depending on the structural and ionic characteristics of the two components in the mixture. Associative phase occurs between two oppositely charged polymers electrostatic interaction and leads to the phase separation, where one phase is enriched with two different biopolymers. Segregative phase happens in two ways, due to strong electrostatic repulsion between two similarly charged biopolymers or for very high steric exclusion between two neutral biopolymers [ ].
Another type of interactions can occur between proteins and polysaccharides, such as covalent bonds, known as conjugated, forming very stable structures. Also non-covalent interactions such as hydrophobic, hydrogen bonding and van der Waals forces can occur [ ]. Diverse physicochemical factors can affect the formation and stability of the complexes such as pH, ionic strength, radio of pectin to protein, pectin and protein charge, and molecular weight, thus the predominant interaction is associated with ionic bonds and the charge density is determinant in the formation of the complex.
Parameters like decrease of the charge density of pectin by partial esterification of the carboxyl groups, increment of the ionic strength or lowering pH can reduce the ability to interaction between thesebiopolymers [ , , ]. Diverse authors have studied the interaction between pectin and proteins. McClements [ ] established that mixtures of protein and polysaccharides can be used to fabricate particles, nanoparticles, among others, with a variety of different compositions, structures and dimensions in dependence of the nature of the polymers involved and the assembly principle used.
In example, in , Jones et al. These authors infer that the particles obtained may be useful for encapsulation and delivery of bioactive food compounds. In this regard, Jones et al. On the other hand, Jensen et al. Figure 9 shows the electrostatic interaction that occurs between the negatively charged pectin and the positively charged casein molecules at different pH values. Stabilization of casein molecule with the pectin network.
At pH 6. At pH 4, pectin bound electrostatically to the positively charged areas of casein particles, preventing casein aggregates [ ]. Gelatin is one of the food biopolymers which has been more studied. Chemically it is considered as a denatured collagen. The interaction between gelatin and pectin has been reported for several authors. These mixes of biopolymers are usually used in formulas of food products and the interactions between them are given through two phenomena to form a gel structure: the first phenomenon is the phase separation that includes two mechanisms type, the segregative also called thermodynamic incompatibility and the associative also called complex coacervation interactions Figure In an associative phase separation one of the separating phases is enriched in both polymers, while in a segregative phase each phase is enriched in one of the polymers [ ].
Gilsenan et al. Schematic illustration of the electrostatic interactions that occur during acidification of gelatin and pectin mixtures a gelatin and pectin molecules exist as individual molecules in solution due to electrostatic repulsion; b gelatin—pectin soluble complexes are formed due to electrostatic attraction between positive charges on gelatin and negative charges on pectin; c soluble complexes merge and form gelatin—pectin complexes; d hydrogel particles form due to coalescence of sub-units; and e setting of internal structure as temperature cools down [ ].
The second phenomenon is the gelation of each polymer or of the association of polymers together, depending of the type of interactions that occurs between them. The gelation process happens when the viscosity of the mixture increases followed by the formation of a network of infinite size, expanding the whole volume and finally stopping the phase separation phenomenon. Factors as rigidity, charge density, solubility may affect the way the polymers interact in the complex system [ ]. Lui et al. For its part, diverse authors establish that the rheological properties of hydrogel particles are affected by parameters as particle shape, size and size distribution [ , , ].
Gupta et al. The fabricated hydrogel did not exhibit any phase separation, having promising uses in biomedical technology. As mentioned above the gelatin pectin complex can be used in the food industry, for example to confer texture to food since these complexes have similar rheological properties as starch granules, a polymer widely used in the food industry [ , ]; or may be a promising product in the subject of healthy reduced-calorie foods for the source of obtainment, protein and dietary fibers [ ].
The rheological, physical and chemical properties of these mixtures have been widely studied; Autio et al. Higher content of calcium Ca and the presence co solutes sucrose in the mixture had faster gelling rates than the gels formed separately. Gels with the lowest Ca content in the mixture affected the sensory profile obtaining gels smoother, more elastic and firm with respect to the other mixtures. Khondkara et al. The use of a cross linker had a considerable influence on the rheological and physicochemical properties of the gels and the study revealed that the cross links between these polysaccharides can occur in mixed polymer systems.
A similar study was reported by Carbinatto et al. The results obtained by these authors coincide with the results obtained by the authors mentioned above; the use of sodium trimetaphosphate leads the formation of gels with higher thermal stability through the formation of covalent bonds. Likewise, potential industrial uses of these polysaccharide combinations are include, as water soluble pouches for detergents and insecticides, flushable liners and bags, and in food industry as edible bags for soup and noodle ingredients [ ].
Dafe et al. The entrapment of probiotics in the matrix was successful and resisted the simulated gastric conditions, increasing the tolerance of L. Diverse authors have also studied the release of the drug diclofenac in matrixes of starch and pectin [ , ]. The existing information related to the interactions between pectin and arabinoxylan is low. To date it is known that the gelling mechanisms of both polymers, in part lies in the presence of ferulic acid in their structures which allows the formation of gels stronger and stable at temperature and pH conditions, mainly for arabinoxylans.
It is well known that the main gelling methods for pectins will depend to a large extent on their degree of methoxylation, although as mentioned previously the presence of ferulic acid in some type of pectins gives it complementary mechanism of gelation by oxidative coupling. Up to this review, authors found little information on the interaction of these polysaccharides in relation to the covalent linkages that may occur between ferulic acid residues in theory.
Nevertheless, some studies have been carried out for the evaluation of microspheres composed of pectin and arabinoxylans. Confocal Laser Scanning Microscopy image. The authors suggested that the composite material formed is a suitable candidate for fabrication of microparticles with little variation in size, a critical feature for the prediction of delivery and accurate doses administration. Also, they envisioned further investigations in vitro and in vivo, to fully understand the diffusional kinetics and mechanisms of such a composite matrix.
In addition, due to their diverse chemical structure they can interact with equally varied type of molecules with promising uses in the pharmaceutical industry, health care and treatment, controlled drug delivery matrix of bioactive materials, and specifically colon targeted ones for their capacity to resist acidic conditions. The impact of this polymer is derived from its good gelation, low cost, non-toxicity, high stability, and biocompatibility. The extensive bioavailability in nature is remarkable, since pectins can be extracted almost from any source of dicotyledonous plants, and also from the transformation of agro-industrial wastes, such as husks and fruit bagasse and pomace.
Traditionally, pectins are obtained from citrus or apple fruits, but in recent years the use of unconventional sources has become an attractive form to obtain pectins from sunflower head residues, mango waste, amaranth, sugar beet, among others. The structural properties of pectin such as degree on esterification, molecular weight, pectin concentration, ion concentration and extrinsic factors as pH, ionic strength and temperature directly affect the gelation process. The presence of ferulic acid in the structure of pectin in plants like sugar beet gives them another gelling mechanism by the ability to gel by oxidative coupling.
The continuous study of pectin structure and its properties has enabled a mayor understanding of the complex heterogeneity of this polysaccharide, and continued development of new applications of pectin beyond the traditional uses in food, as pharmaceutical industries are increasingly embracing renewable and biocompatible materials. The perspectives of the new composites are the most promising in controlled and targeted delivery of therapeutic molecules with high potential in the reduction of doses of antibiotics required as well as new vehicles for oral administration of otherwise sensitive molecules like insulin.
The anticancer, antiobesity and heavy metal-binding capacity has been well documented and will be of great impact in human health in the short term. National Center for Biotechnology Information , U. Journal List Molecules v. Published online Apr Author information Article notes Copyright and License information Disclaimer. Received Mar 16; Accepted Apr This article has been cited by other articles in PMC. Keywords: pectin, pectin composites, therapeutic properties, drug delivery system. Introduction Pectins are plant cell wall structural polysaccharides composed mainly of galacturonic acid units with variations in composition, structure and molecular weight.
Chemical Structure The exact chemical composition and structure of pectin is still under debate due to the high complexity of this molecule. Rhamnogalacturonan-II RG-II RG-II has a highly conserved structure and consistsofa linear backbone chain of galacturonic acid units, substituted with l -rhamnose, d -galactose and many unusual sugars, such as apiose, aceric acid, 3- O -methyl- l -fucose, 2- O -methyl- d -xylose, 3- C -carboxydeoxy- l -xylose, 3-deoxy- d -manno-octulosonic acid and 3-deoxy- d -lyxo-heptulosaric acid [ 30 , 46 , 54 ]. Biosynthesis of Pectin Though pectins have been reported since the s, pectin biosynthesis is a subject of study still under development due to its complex structure.
Open in a separate window. Figure 1. Sources 1. Traditional Sources Pectin can be found in almost all plants, but commercially most pectins are obtained from citrus fruits like orange, lemons, grapefruit, and apples [ 64 , 65 ]. Unconventional Sources In recent years, the search of new sources of pectin appears very promising.
Ferulated Pectins Ferulic acid is a component of some plant families, where it can be esterified to cell-wall polysaccharides. Gelling Mechanisms One of the main characteristics and attractiveness of pectins is their capacity to form gels. Figure 2. Ferulated Pectins Crosslinking It is well known that ferulic acid is linked to polysaccharides like pectins in many plants and that it is possible to form gels through oxidative coupling [ , , ].
Potential Applications of Pectin in Pharmaceutical and Biomedical Industry Pectin, as a natural polymer in many fruits, possesses many interesting properties that have been widely exploited in food technology, and studied in the biomedical and pharmaceutical fields. Sugar beet pulp NA [ ]. Roots of Bupleurum falcatum NS [ , ]. Apple pomace, tangerine peel and wild plant NA [ ].
Glucose levels Passiflora glandulosa 35 [ ]. Unripe apple NS [ ]. Citrus pectin NS [ , ]. Cholesterol leves Soluble dietary fiber NA [ , , ]. Banana passion fruit 52 [ ]. Metal removal Seagrass, citrus pectin 60 [ , , ]. Seagrass P. Citrus pectin 3. Citrus pectin NS [ ]. Citrus pectin 1 [ ]. Cancer prevention Modified pectin NS [ ]. Prostate cancer Modified citrus pectin NS [ ].
Citrus pectin P 6. Pancreatic cancer Flowers of L. Breast cancer Pectic polysaccharides NS [ ]. Metastasis Modified citrus pectin NS [ , ]. Modified citrus pectin 6. Pumpkin 5. Antiproliferative effect Citrus pectin NS [ ]. Modified sugar beet 18,55,57,62 [ ]. Modified citrus pectin NS [ ]. Gen delivery Amidated citrus pectin 26 [ ]. Tissue engineering Modified pectin with oligopeptides LM [ , ]. Wound healing Amidated pectin LM [ , ]. Drug encapsulation Citrus, pumpkin 48,44;8.
Fentanyl Pectin NA [ , , ]. Ocular drug delivery Mucoadhesive polymers NA [ , ]. Colon drug delivery Citrus pectin 36,25; 10,35 [ , , , , , ]. Prebiotic Effect In general, prebiotics are defined as indigestible food ingredients that beneficially affect health through various mechanisms [ ]. Effect on Glucose Levels Several studies have shown the positive effect of pectin in the reduction of blood glucose.
Effect on Cholesterol Levels The study of the relationship between cholesterol and the consumption of pectins has been studied extensively over the years through studies in vivo and in vitro. Figure 3. Removal of Metal Ions Toxic metals as arsenic, cadmium, lead and mercury interrupt the normal functioning of the endocrine, neurological and immune systems, in addition to other functions in the human body.
Figure 4. Cancer Prevention Another promising feature of pectin is its apparent synergism and chemoprotective action on metastasis of cancer and the growth of primary tumors in multiple types of cancer in human and animals. Figure 5. Pectin as a Drug Controlled Release Matrix The use of pectin as a matrix for the controlled delivery of drugs has raised interest in recent years mainly in biomedical applications such as drug delivery [ 14 , 18 ], gene delivery [ ], tissue engineering [ , ], wound healing [ ] and wound dressing material [ ], for its capacity to form stable gels and its simple gelling mechanism.
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