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Xanthan Gum is a long-chain polysaccharide-based excipient having D-Glucose, D-Mannose, and D-Glucuronic acid as building blocks in a molecular ratio of 3:3:2 with a high number of trisaccharide side chains. It is a product of fermentation of a suitable sugar source using pure cultures of the micro-organism Xanthomonas campestris and has an average molecular weight of about 2000 kDa. Xanthan gum is supplied in the form of a cream or white-coloured free-flowing powder that has no perceptible odour or taste.
Pharmacopoeial Compliance: USP-NF; Ph.Eur; B.P; J.P; I.P
Synonyms and Trade Names: Xanthan gum; Corn sugar gum; E415; Grindsted; Keldent; Keltrol; Polysaccharide B-1459; Rhodigel; Vanzan NF; Xantural
Uses and Applications: Gelling Agent; Stabilising Agent; Suspending Agent; Sustained-Release Agent; and Viscosity-Increasing Agent
Xanthan gum is a high-molecular-weight polysaccharide (whose building blocks are D-glucose, D-mannose, and D-glucuronic acid in a molar ratio of 3:3:2) produced by aerobic fermentation of dextrose solutions using pure cultures of the micro-organism Xanthomonas campestris. The gum is recovered by precipitation with isopropyl alcohol.
Xanthan gum was discovered in the 1960s by scientists at the United States Department of Agriculture. It was subsequently commercialised by CP Kelco and availed to the market in the early 1970s following approval for use as a food additive in 1969. Currently, Xanthan gum is widely approved as a food hydrocolloid and pharmaceutical excipient across the world. In Europe, it is also known as E415.
Xanthan gum is assigned the empirical formula (C35H49O29). The primary structure consists of the cellulose-like backbone of (1, 4)-linked D-glucose residues substituted alternate glucose residues with a trisaccharide side chain. The trisaccharide side chain consists of two mannose separated by a glucuronic acid. Approximately half the terminal mannose units are linked to a pyruvate group and the non-terminal residue usually carries an acetyl group. The carboxyl groups on the side chains render Xanthan gum molecules anionic. In all, the molecular weight of xanthan gum ranges from 300 kDa to 8 MDa.
The USP-NF describes xanthan gum as a high molecular weight polysaccharide gum that contains D-glucose and D-mannose as the dominant hexose units, along with D-glucuronic acid, and is prepared as the sodium, potassium, or calcium salt. The USP-NF also includes a monograph for xanthan gum solution. ICommercial grades available in several different grades that have varying particle sizes. Fine-mesh grades are used in applications where high solubility is desirable since they dissolve rapidly in water. However, fine-mesh grades disperse more slowly than coarse grades and are best used dry blended with the other ingredients of a formulation.
Xanthan gum occurs as a cream- or white-coloured, odourless, free-flowing, fine powder. In water, Xanthan gum yields high-viscosity solutions that are pseudoplastic, unusually stable to high temperatures, and little change in viscosity as temperature changes.
|Chemical Name||Xanthan gum|
|CAS Registry Number||[11138-66-2]|
|Molecular Weight||1xl06 Daltons|
|UNII Code (FDA)||TTV12P4NEE|
Xanthan gum is an approved pharmaceutical excipient and currently listed in all the major pharmacopoeia. It is also GRAS listed and accepted for use as a food additive in Europe. It is included in the FDA Inactive Ingredients Database (covering oral solutions, suspensions, and tablets; rectal and topical preparations). A specification for xanthan gum is contained in the Food Chemicals Codex (FCC).
|Physical form||Solid, powder|
|Appearance||Cream or white-coloured powder. Solutions are clear to translucent depending on concentration|
|pH (1% w/v aqueous solution)||6.0-8.0|
|Freezing point||0 oC for a 1% w/v aqueous solution|
|Nutritional value||210 kJ (50 kcal) per 100g|
|Heat of combustion||14.6 J/g|
|Melting point||Chars at 270 oC.|
|Particle size distribution||Various grades with different particle sizes are available.|
|Refractive index||= 1.333 (1% w/v aqueous solution)|
|Solubility||Soluble in cold or warm water. Insoluble in ethanol|
|Viscosity (1% w/v solution)||1200-1600 cP at 25 C.|
|Official name||Xanthan gum||Xanthan gum|
|Viscosity||≥ 600 mPa s||≥ 600 mPa s|
|Propan-2-ol||≤ 0.075%||≤ 750 ppm|
|Loss on drying||≤ 15.0%||≤ 15.0%|
|Total ash||6.5 -16.0%||6.5 -16.0%|
|Bacteria||n/a||≤ 103 cfu/g|
|Fungi||n/a||≤ 102 cfu/g|
|Pyruvic acid||≤ 1.5%||n/a|
|Heavy metals||≤ 0.003%||n/a|
Key: n/a Specification is not listed
*All claims with respect to conformity are subject to our Terms and Conditions. No express or implied warranty is made for specific properties or fitness for any particular application or purpose.
Xanthan gum functions as a stabilizing agent; gelling agent, suspending agent, sustained-release agent and viscosity-increasing agent. It is a fast-hydrating water-soluble hydrocolloid that can be dissolved at room temperature.
Xanthan gum is extensively used in oral and topical pharmaceutical products, foods and cosmetics as a suspending and stabilizing agent. It is also used as a thickening and emulsifying agent. It exhibits excellent stability and viscosity properties over a wide pH and temperature range.
Xanthan gum gels exhibit pseudoplastic rheological properties, such that the decrease in viscosity is directly related to the applied shear rate. The viscosity returns to normal immediately upon the removal of the shear stress.
Xanthan gum has been used as a suspending agent for conventional, dry and sustained-release suspensions. When xanthan gum is mixed with certain inorganic suspending agents, such as Magnesium aluminium silicate, or organic gums, synergistic rheological effects are obtained. Thus, blends of Xanthan gum and Magnesium aluminum silicate are used in ratios between 1:2 and 1:9 to produce optimum rheological properties. In addition, optimum synergistic effects are observed when Xanthan gum is combined with Guar gum, typically in ratios between 3:7 or 1:9.
While the primary function of Xanthan gum is as a viscosity-increasing excipient, it has also been used to fabricate sustained-release matrix tablets taking advantage of its gel-forming properties. Xanthan gum has also been used to formulate directly compressed matrix tablets that exhibit high levels of swelling as a result of water intake, and limited erosion from polymer chain relaxation. Xanthan gum has reportedly been used in combination with Chitosan, Guar gum and Sodium alginate to formulate sustained-release matrix tablets.
In ophthalmic formulations, Xanthan gum is used as a bioadhesive gelling agent, which interacts with mucin, enabling prolonged contact of the dosage form to the corneal membrane. When included in liquid ophthalmic products, Xanthan gum can help delay the release of active drug substances, thereby enhancing the therapeutic effect of the pharmaceutical product, and improving patient experience.
Xanthan gum may also be utilised to improve the bioadhesive strength of various gels (for instance, vaginal formulations and ultrasound gels). Either alone or in combination with Carbomer 974, Xanthan gum can be used as a mucoadhesive controlled-release excipient for buccal drug delivery. Several active pharmaceutical ingredients, including Atenolol, Ibuprofen and Vitamin A have been successfully formulated using films, microemulsions or lipid nanoparticles leveraging the gelling properties of Xanthan gum. A formulation combining Xanthan gum, Carboxymethylcellulose sodium and Povidone polymers has been used to relieve symptoms of dry mouth (xerostomia).
Xanthan gum is also used widely as a hydrocolloid in the food industry, as well as a gelling agent in several cosmetic products. It functions as a thickening agent and viscosity modifier in shampoos and shower gels.
Xanthan gum is widely used in oral and topical pharmaceutical formulations, cosmetics, and food products, and is generally regarded as nontoxic and non-irritant at the levels employed as a pharmaceutical excipient.
The estimated acceptable daily intake for xanthan gum has been set by the WHO at up to 10 mg/kg body-weight.
No eye or skin irritation has been observed in rabbits and no skin allergy has been observed in guinea pips following skin exposure1. No adverse effects were observed in long term feeding studies with rats (up to 100mg/kg/day) and dogs (up to 1000 mg/kg/day). No adverse effects were observed in a three-generation reproduction study with rats (up to 500mg/kg/day)
Toxicology: LD50 (rat; oral): > 45g/kg
Xanthan gum is generally a stable excipient. Typical shelf life is given as 24-36 months if the material is handled correctly. The bulk material should be stored in a well-closed container in a cool, dry place.
Aqueous solutions are also stable between the pH range of 3-12, although the ideal pH is 4-10 (at temperatures of 10-60 oC). Xanthan gum exhibits excellent thermal stability, and will generally provide the same thickening, stabilizing, and suspending properties during long-term storage at elevated temperatures. Additionally, Xanthan gum shows excellent freeze-thaw stability. Solutions are unaffected by the presence of enzymes, salts, acids, and bases. However, since Xanthan gum is an anionic, compatibility with cationic surfactants, polymers, or preservatives is compromised and precipitation may ensue. Anionic and amphoteric surfactants (at concentrations >15% w/v) may also result in the precipitation of Xanthan gum from its solutions.
Xanthan gum is compatible with most synthetic and natural viscosity-increasing agents, mineral acids, and inorganic salts (up to 30%). When used together with Cellulose ether polymers, Xanthan gum that is free of the enzyme cellulase is recommended in order to eliminate the possibility of de-polymerising the cellulose polymer. However, Xanthan gum solutions are compatible with water-miscible organic solvents (for example, acetone, methanol, ethanol, or isopropanol) in concentrations of <60%.
When handling Xanthan gum in the workplace, it is highly recommended to observe SHEQ protocols appropriate to the circumstances and quantity of material handled. The use of suitable eye protection and gloves is recommended.
Xanthan gum is a nature-derived carbohydrate produced by aerobic fermentation of glucose or sucrose solutions. As a biodegradable and non-toxic substance, Xanthan gum is considered safe for the environment with minimal long-term impact on ecology or marine life. Xanthan gum achieved a total score of 80/100 by the Excipients Forum Sustainable Chemistry Score™ scheme.
. A.P. Imeson, Thickening and Gelling Agents for Food, 1995.
. G.O. Phillips, P.A. Williams, D.J. Wedlock, Gums and Stabilisers for the Food Industry, 1996.
. M.J. Tobyn, J.R. Johnson, P.W. Dettmar, Factors affecting in vitro gastric mucoadhesion. IV. Influence of tablet excipients, surfactants and salts on the observed mucoadhesion of polymers, European Journal of Pharmaceutics and Biopharmaceutics, 43 (1997) 65-71.
. F. Garcı́a-Ochoa, V.E. Santos, J.A. Casas, E. Gómez, Xanthan gum: production, recovery, and properties, Biotechnology Advances, 18 (2000) 549-579.
. D.R. Karsa, R.A. Stephenson, Excipients and Delivery Systems for Pharmaceutical Formulations, 2002.
. M.D. Torres, R. Moreira, F. Chenlo, M.J. Vazquez, Water adsorption isotherms of carboxymethyl cellulose, guar, locust bean, tragacanth and xanthan gums, Carbohydr Polym, 89 (2012) 592-598.
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