Available online on www.ijppr.com
`International Journal of Pharmacognosy and Phytochemical Research 2014-15; 6(4); 901-912
`
` ISSN: 0975-4873
`Review Article
`
`Natural Gums and Mucilages: A Review on Multifaceted Excipients in
`Pharmaceutical Science and Research
`
`Rohit Rajendra Bhosale, Riyaz Ali M. Osmani, *Afrasim Moin
`
`Department of Pharmaceutics, JSS College of Pharmacy, Mysore, Karnataka, India.
`
`Available Online: 22nd November, 2014
`
`
`ABSTRACT
`The application of natural polysaccharides in novel drug delivery systems to deliver the bioactive agents has been hampered
`by the synthetic polymers. The main benefits of the natural polysaccharides are their being biodegradable, biocompatible,
`non-toxic, richly available and less expensive. Because of the advances in drug delivery technology, natural
`polysaccharides are included in novel drug delivery to fulfill multitask functions and in some cases directly or indirectly
`control the extent and/or rate of drug release. Substantial research efforts have been directed towards developing safe and
`efficient natural based polysaccharide particulate drug delivery systems. The present review outlines the natural based
`polysaccharides, natural gums and mucilages and their isolation, purification, standardization and characterization
`characteristics along with their applications are covered. Also this review covers fabrication techniques for natural
`polysaccharide based particulate drug delivery systems, specifically micro and nanoparticle drug delivery systems with
`their characterization techniques and applications are discussed.
`
`Keywords: Natural Polysaccharides; Natural gums and mucilages; Standardization; Applications; Modification.
`
`INTRODUCTION
`In this developing world, there is an immense demand for
`novel drug delivery systems, and there is a noteworthy
`increase in the approvals of similar systems. Natural
`excipients and their application in the pharmaceutical
`industry are super imposed by the presence of synthetic
`excipients. Natural excipients are preferred over the
`synthetic as they are inert, safe, non-toxic, biocompatible,
`biodegradable, low cost, eco-friendly and abundantly
`available in nature.1-3 Conventionally, excipients were
`incorporated in dosage forms as inert vehicles but in
`modern pharmaceutical dosage
`forms
`they often
`accomplish multitask roles such as improvement of
`solubility of poorly soluble drugs enhance bioavailability,
`desired drug release, target specific in the form of
`microparticles, and nanoparticles.4 Most of natural
`polysaccharides used in the food industry are regarded as
`safe for human consumption.
`Natural polysaccharides are often included in the design of
`controlled drug delivery such as those target delivery of the
`drug to a specific site in the gastro intestinal tract (GIT),
`this can be achieved by various mechanisms including
`coating granules, pellets, tablets with polysaccharides
`having pH dependent solubility, or incorporating non-
`digestible polysaccharides that are degraded by bacterial
`enzymes present in the colon, this property makes these
`polysaccharides potentially useful in the formulation of
`colon-targeted drug delivery systems. The polysaccharides
`can also be modified in different ways to obtain tailor-
`made materials for drug delivery systems and thus can
`compete with the available synthetic excipients. With the
`
`increasing interest in excipients of natural origin, the
`pharmaceutical world has compliance to use most of them
`in
`their
`formulations. Moreover,
`the
`tremendous
`orientation of pharma world towards these naturally
`derived polysaccharides has become a subject of
`increasing interest to discover, extract and purify such
`compounds from the reported origin. The focus should be
`directed towards the development of the newer excipients,
`so that they can enter the pharmaceutical industry and
`newer formulations could be developed and formulation
`problems could be solved.5, 6
`Natural Polysaccharides: Polysaccharides are composed of
`many monosaccharide residues that are joined one to the
`other by O-glycosidic linkages. Polysaccharides are
`commonly known as Cinderella of biopolymers, with wide
`range of applications.7
`Their structures are often linear, but may contain various
`degrees of branching. In nature, polysaccharides have
`various resources from algal origin, plant origin, microbial
`origin and animal origin .Polysaccharides have a general
`formula of Cx(H2O)y where x is usually a large number
`between 200 and 2500. Considering that the repeating
`units in the polymer backbone are often six-carbon
`monosaccharides,
`the general formula can also be
`represented as (C6H10O5)n where 40≤ n ≤3000.8-10
`Classification of Natural Polysaccharides: Polysaccharides
`are extracted and isolated from plant seeds. (locust bean
`gum, guar gum, tara gum, and tamarind gum). They also
`play a major role in the structural integrity and mechanical
`strength of plant tissues by forming a hydrated cross-linked
`
`*Author for correspondence
`
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`Rohit Rajendra Bhosale et al. / Natural Gums and…
`
`Table 1: Preliminary confirmative test for dried mucilage
`Test
`Molisch’s test:
`100 mg dried mucilage powder + Molisch’s reagent +
`conc. H2SO4 on the side of a test tube.
`Ruthenium test:
`Take a small quantity of dried mucilage powder, mount it
`on a slide with ruthenium red solution and observe it under
`microscope.
`Iodine test:
`100 mg dried mucilage powder + 1 ml 0.2 N iodine
`solution.
`Enzyme test:
`Dissolve 100 mg dried mucilage powder in 20 ml distilled
`water; add 0.5 ml of benzidine in alcohol (90%). Shake
`and allow to stand for few minutes.
`three dimensional network (pectin). On the other hand,
`cellulose an essential ingredient of the cell wall in higher
` plants is most abundantly available biopolymer present in
`the nature.
`Another most important classification of polysaccharide
`are tree exudates with an history of 5,000 years which are
`known for their properties like thickening, emulsifying,
`stabilizing, binding agents and matrix formers in both food
`and pharmaceutical industry (gum acacia, gum tragacanth
`and gum karaya). Gums are present in huge quantities in
`varieties of plants, animals, marine and microbial sources.
`Plant gums are very common with different structural and
`metabolic
`functions commonly
`found
`in
`family
`Leguminosae, Sterculiaceae, Bixaceae, Compositae,
`Combretaceae, Gigarginaceae.
`The different available polysaccharides can be classified as
`follows.8-11
`Based on the ionic charge: Gums have been classified into
`anionic, cationic and non-ionic. a) Anionic charged gums:
`tragacanth, arabic, karaya, gellan, agar, pectin, algin,
`carrgeenans. b) Cationic charged gums: chitosan. c) Non-
`ionic charged gums: guar gum, locust bean gum, tamarind
`gum, arabinans, xanthan gum, amylase, cellulose.
`Based on the origin: a) Marine (sea weeds gum): alginates,
`agar, Carrageenans. b) Animal origin: chitin and chitosan,
`Chondroitin sulfate, hyaluronic acid. c) Plant origin: i)
`Seed gums–locust bean, guar, starch, cellulose, amylase.
`ii) Tree exudates-gum arabia, tragacanth, ghatti, karaya.
`iii) Tubers-Potato starch. iv) Extracts-pectin. d) Microbial
`origin (fungi and bacteria): glycan, pullulan, dextran,
`xanthan, gellan.
`Based on the shape: a) Linear: amylase, pectin, cellulose.
`b) Branched: i) Short branched-guar gum, locust bean
`gum; ii) Long branched-amylopectin, karaya gum, gum
`tragacanth, gum arabic.
`Natural Gums and Mucilages: Gums are considered to be
`pathological products formed following injury to the plant
`or owing to unfavorable conditions, such as drought, by a
`breakdown of cell walls (extra cellular formation;
`gummosis) while, mucilages are generally normal
`products of metabolism,
`formed within
`the cell
`(intracellular formation) and/or are produced without
`injury to the plant. Gums readily dissolve in water,
`
`Observation
`Violet green color observed at
`the junction of the two layers
`
`Inferences
`Carbohydrate present
`
`Pink color develops
`
`Mucilage present
`
`No blue color produced
`
`No color observed in solution Polysaccharides
`present (starch is
`absent)
`Enzyme absent
`(Distinction
`between dried
`mucilage and acacia)
`whereas, mucilage form slimy masses. Gums are
`pathological
`products, whereas mucilages
`are
`physiological products. Acacia, tragacanth, and guar gum
`are examples of gums while mucilages are often found in
`different parts of plants. For example, in the epidermal
`cells of leaves (senna), in seed coats (linseed, psyllium),
`roots (marshmallow), barks (slippery elm) and middle
`lamella (aloe). Gums and mucilages have certain
`similarities- both are plant hydrocolloids. They are also
`translucent amorphous substances and polymers of a
`monosaccharide or mixed monosaccharides and many of
`them are combined with uronic acids. Gums and mucilages
`have similar constituents and on hydrolysis yield a mixture
`of sugars and uronic acids. Gums and mucilages contain
`hydrophilic molecules, which can combine with water to
`form viscous solutions or gels. The nature of the
`compounds involved influences the properties of different
`gums. Linear polysaccharides occupy more space and are
`more viscous than highly branched compounds of the same
`molecular weight. The branched compounds form gels
`more easily and are more stable because extensive
`interaction along the chains is not possible.12
`in
`Advantages of Natural Gums and Mucilages
`Pharmaceutical Sciences: The following are a number of
`the advantages of natural plant–based materials.13, 14
` Biodegradable- Naturally available biodegradable
`polymers are produced by all living organisms. They
`represent truly renewable source and they have no
`adverse impact on humans or environmental health.
` Biocompatible and non-toxic- Chemically, nearly all of
`these plant materials are carbohydrates composed of
`repeating sugar (monosaccharides) units. Hence, they
`are nontoxic.
` Low cost- It is always cheaper to use natural sources.
`The production cost is also much lower compared with
`that for synthetic material. India and many developing
`countries are dependent on agriculture.
` Environmental-friendly
`and
`processing- Gums
`mucilages from different sources are easily collected in
`different seasons in large quantities due to the simple
`production processes involved.
`
`IJPPR, Vol-6, Issue 4, December 2014- January 2015, 901-912
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`Rohit Rajendra Bhosale et al. / Natural Gums and…
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`Guar gum
`
`Gellan gum
`
`USP, PhEur
`
`USP
`USP, PhEur
`
`USP, JP, PhEur
`
`USP, PhEur
`
`USP
`
`Pharmacopeia
`USP, JP, PhEur
`USP, PhEur
`USP
`USP, BP, JP
`USP, JP, PhEur
`
`Table 2: Pharmacopoeial Specifications for Natural Gums and Mucilages
`Excipient
`Test
`Acacia
`Microbial limit, ash values
`Alginic acid Microbial limit, pH, loss on drying
`Carrageenan
`Solubility, viscosity, loss on drying, ash value
`Dextrin
`Loss on drying, residue on ignition, reducing sugars
`Gelatin
`Isoelectric point, microbial limit, residue on ignition,
`loss on drying, total ash, jelly strength
`pH, microbial contamination, apparent viscosity, loss
`on drying, ash, galactomannans, organic volatile impurities
`Water, arsenic, lead, acid value, heavy metals
`Lecithin
`Microbial limit, appearance of solution, loss on
`Sodium
`drying, ash, heavy metals
`alginate
`Tragacanth Microbial limits, flow time, lead, acacia and other
`soluble gums, heavy metals
`Xanthan gum pH, viscosity, microbial limits, loss on drying, ash,
`heavy metals, organic volatile impurities
`pH, microbial limit, loss on drying, moisture
`content, specific gravity, solubility, bulk density
`Baveja et al., and Wahi et al., reported the following
` Local availability (especially in developing countries)-
`method for the isolation of mucilage. The fresh plant
`In developing countries, governments promote the
`materials were collected washed with water to remove dirt
`production of plant like guar gum and tragacanth
`and debris, and dried. Then, the powdered material was
` because of the wide applications in a variety of
`soaked in water for 5-6 h, boiled for 30 min, and allows
`industries.
`standing 1 h so that all the mucilage was released into the
` Better patient tolerance as well as public acceptance-
`water. The material was then squeezed from an eight
`There is less chance of side and adverse effects with
`muslin bag to remove the marc from the solution.
`natural materials compared with synthetic one. For
`Following this, three volumes of acetone was added to the
`example, PMMA, povidone.
`filtrate to precipitate the mucilage. The mucilage was
` Edible sources- Most gums and mucilages are obtained
`separated, dried in an oven at a temperature less than 50˚C,
`from edible sources.
`and the dried powder was passed through a No. 80 sieve
`Disadvantages of Natural Gums and Mucilages: The
`and stored in a desiccator until required. The isolated
`following are a number of the disadvantages of natural
`mucilage from the plant was subjected to some preliminary
`plant–based materials.13, 14
`confirmative testing.
` Microbial contamination- The equilibrium moisture
`Table No. 1 shows the preliminary confirmative test for
`content present in the gums and mucilages is normally
`dried mucilage.15, 16
`10% or more and, structurally, they are carbohydrates
`Extraction is one of the most crucial procedures to achieve
`and, during production, they are exposed to the external
`complete recovery of target compounds from plants.
`environment and, so there is a chance of microbial
`Recently, microwave energy has started to be used for the
`contamination. However, this can be prevented by
`extraction of phytoconstituents from plants. It is a simple,
`proper handling and the use of preservatives.
`fast, clean, eco-friendly and efficient method and saves
` Reduced viscosity on storage- Normally, when gums
`energy, fuel and electricity.17
`and mucilages come into contact with water there is an
`Microwave extraction follows the same principle as
`increase in the viscosity of the formulations. Due to the
`maceration or percolation, but the speed of breaking up of
`complex
`nature
`of
`gums
`and mucilages
`the plant cells and tissues is much higher. Microwave
`(monosaccharides
`to polysaccharides
`and
`their
`assisted extraction methods require a shorter time and less
`derivatives), it has been found that after storage there is
`solvent, and provide a higher extraction rate and better
`reduced in viscosity.
`products at a lower cost. Plant material is powdered in a
`Isolation and Purification of Natural Gums and Mucilages:
`mechanical blender for 5 min and then soaked in distilled
`Plant material is dried in sunlight (preferably) or in an oven
`water for 24 hrs in a 1000 ml beaker. It is kept in a
`at 105˚C to retain its properties unchanged. Generally,
`microwave oven along with a glass tube to prevent
`chlorophyll or pigments are present in the plant which
`bumping when subjected to microwave irradiation. The
`should be removed before isolating the mucilage. Plant
`beaker is removed from the oven and allowed to stand for
`material must be treated with petroleum ether and
`2 hrs to allow the mucilage to be released into the water. It
`chloroform (to remove pigments and chlorophyll) and then
`is then processed in a similar way to the conventional
`with distilled water. Care should be taken when drying the
`procedure, weighed and stored.17
`final isolated/extracted mucilage. It must be dried at a very
`Characterization and Standardization of Natural Gums and
`low temperature (not more than 50˚C) or in a vacuum. The
`Mucilages: A suitable strategy is required to save money
`dried material is stored carefully in desiccators to prevent
`and time. Over-characterization is not desirable, because
`further moisture uptake or degradation.
`excessive use of time and resources could actually delay
`
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`Table 3: Pharmaceutical Applications of Natural Gums and Mucilages
`Common
`Botanical Name
`Family
`Name
`Albizia gum
`Asario Mucilage
`
`Leguminoseae
`Cruciferae
`
`Albizia Zygia
`Lepidum Sativum
`
`Bavchi Mucilage
`
`Ocimum Canum
`
`Cashew gum
`Guar gum
`
`Gum acacia
`
`Anacardium occidentale
`Cyamompsis
`tetraganolobus
`Acacia Arabica
`
`Gum ghatti
`
`Gum
`Tragacanth
`
`Anogeissus
`Latifolia
`Astragalus
`Gummifer
`
`Karaya gum
`
`Sterculiaurens
`
`Khaya gum
`Sodium alginate
`
`Khaya grandifolia
`Macrocytis pyrifera
`
`Labiatae
`
`Anacardiaceae
`Leguminoseae
`
`Leguminoseae
`
`Combretaceae
`
`Leguminoseae
`
`Sterculiaceae
`
`Meliaceae
`Lessoniaceae
`
`Xanthan gum
`
`Xanthomonas lempestris
`
`-
`
`-
`
`Pseudomonas elodea
`Gellan gum
`the launch of innovative excipients.
`The characterization of gums and mucilages is initially
`achieved by only a multiple technique approach.
`For excipient analysis, analytical techniques can be
`classified according
`to
`the
`type of
`information
`generated.18-20
` Structure- Gums and mucilages are polysaccharides and
`contain sugars. So, confirmation of the different sugars
`is carried out by chromatography and structure
`elucidation can be carried out by NMR and mass
`spectroscopy.
` Purity- To determine the purity of the selected gum and
`mucilage, tests for alkaloids, glycosides, carbohydrates,
`flavanoids, steroids, amino acids, terpenes, saponins,
`oils and fats, and tannins and phenols are carried out.
` Impurity profile- Testing for impurities must be carried
`out using suitable analytical techniques.
` Physico-chemical properties- Color, odor, shape, taste,
`touch, texture, solubility, pH, swelling index, loss on
`drying, hygroscopic nature, angle of repose, bulk and
`true densities, porosity and surface tension. Different ash
`values are also estimated. The microbial load and
`presence of specific pathogens are also determined. In
`vitro cytotoxicity
`is also determined. Gums and
`mucilages are highly viscous in nature. So, the
`rheological properties of excipients are important
`criteria for deciding their commercial use. The flow
`behavior of the samples is determined.
` Toxicity- The acute toxicity of gums and mucilages are
`determined by the followings fixed-dose method as per
`
`IJPPR, Vol-6, Issue 4, December 2014- January 2015, 901-912
`
`Reference
`
`34-36
`37, 38
`
`39
`
`40-43
`44-49
`
`50
`
`51
`
`52
`
`53-61
`
`62
`63-71
`
`72-74
`
`Page904
`
`Pharmaceutical
`Applications
`Tablet binder
`Suspending agent,
`emulsifying agent,
`Suspending agent,
`emulsifying agent
`Suspending agent
`Binder,
`emulsifier,
`disintegrant
`Suspending agent,
`emulsifying agent,
`binder in tablets,
`demulcent and
`emollient
`Binder, emulsifier,
`suspending agent
`Suspending agent,
`emulsifying agent,
`demulcent, emollient
`Suspending agent,
`emulsifying agent,
`dental adhesive,
`sustaining agent
`Binding agent
`Suspending and sustained
`release agent
`Suspending agent,
`emulsifier, stabilizer
`Disintegrating agent
`75
`OECD guideline No. 425. A sub-acute toxicity study,
`determination of the LD50 etc., is carried out in rats and
`guinea pigs of both sexes. Once analysis is complete,
`determination of the structure, composition and impurity
`profile enables a scientific dossier to be prepared
`describing the excipient. This information is of value for
`the regulatory dossier of the final pharmaceutical
`product that would contain the given excipient. Finally,
`gums and mucialges are added to pharmaceutical
`formulations. So a compatibility study is important. The
`compatibility studies of gum/ mucilage/ drugs are
`performed using spectrophotometry/ FTIR/ DSC.21-29
`Pharmacopoeial Standard Specifications of Natural Gums
`and Mucilages: Different pharmacopoeias, like USP,
`PhEur, and JP give pharmacopoeial standards for specific
`gums. The Pharmacopoeial standard for different gums is
`shown in Table No. 2.30, 31
`Applications of Natural Gums and Mucilages: Gums and
`mucilages of different sources and their derivatives
`represent a group of polymers widely used
`in
`pharmaceutical dosage forms. Various kinds of gums are
`used in the food industry and are regarded as safe for
`human consumption. However, there is growing concern
`about the safety of pharmaceutical excipients derived from
`natural sources. Plant gums and exudates are now screened
`for their use as pharmaceutical adjuvants. Mucilages of
`different origins are also used in conventional dosage
`forms of various drugs for their binding, thickening,
`stabilizing and humidifying properties in medicine. A
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`Acacia
`Bhara gum
`Chitosan
`
`Acacia Senegal
`Terminalia bellericaroxb
`-
`
`Leguminosae
`Combretaceae
`-
`
`Cordia gum
`
`Cordia oblique willed
`
`Boraginaecae
`
`Guar gum
`
`Gellan gum
`
`Cyamompsis
`Tetraganolobus
`Pseudomonas elodea
`
`Leguminoseae
`
`-
`
`Karaya gum
`
`Sterculiaurens
`
`Sterculiaceae
`
`Table 4: Applications of Natural Gums and Mucilages in Novel Drug Delivery Systems
`Common Name Botanical Name
`Family
`Pharmaceutical
`Applications
`Osmotic drug delivery
`Microencapsulation
`Colon specific drug
`delivery, microspheres,
`nanoparticles
`Oral sustained release matrix
`tablets
`Colon targeted drug
`delivery, microspheres
`Ophthalmic drug delivery,
`sustaining
`agent,beads,
`hydrogels,
`Mucoadhesive and
`Buccoadhesive
`Controlled delivery
`
`Microspheres
`Hydrophilic matrix for
`controlled release drug
`delivery
`Bioadhvesive
`microspheres,
`nanoparticles
`Pellets, controlled drug
`delivery system
`Table 3. Table 4 lists the different applications of gums
`and mucilages in novel drug delivery systems.34-98
` Industrial applications- Gums used in cosmetics (acacia,
`tragacanth and karaya gum), textiles (starch, dextrin,
`cellulose, pectins, and tamarind gum), adhesives (acacia
`gum, and
`tragacanth),
`lithography
`(gum arabic,
`tragacanth, and locust bean gum), paints (pectins,
`hemicellulose, and resins) and paper manufacturer
`(tamarind, and cellulose).
`Modification/Grafting of Natural Polysaccharides, Gums
`and Mucilages: There are various methods for modifying
`the structures of polysaccharides. The introduction of
`hydrophobic, acidic, basic, or other functionality into
`polysaccharide structures can alter the properties of
`materials based on these substances.
`There are two methods for modification or grafting of
`natural polysaccharides: Physical methods and chemical
`Methods.99
`Physical Modification of Polysaccharides
` Physical Cross linking
`forms
`polysaccharides
`In
`physical
`crosslinking,
`crosslinked network with counterion at the surface. High
`counterion concentration would require longer exposure
`times
`to achieve complete crosslinking of
`the
`polysaccharides. For physical crosslinking different
`methods have been investigated such as:
` Cross linking by ionic interaction
` Cross linking by Crystallization
` Hydrophobised polysaccharides
`generate
`Microwave modification: Microwaves
`electromagnetic radiation in the frequency range of 300
`
`Sodium alginate Macrocytis pyrifera
`
`Lessoniaceae
`
`Xanthan gum
`
`Xanthomonas lempestris
`
`-
`
`newer use of different gums and mucilages in cosmetics
`and textiles has increased the demand and screening of
`gums has become an important pharmaceutical area.
`However, different gums and mucilages used as
`pharmaceutical adjuvants have stringent specifications,
`which few natural agents can fulfill.32, 33
`Gums and mucilages have the following applications.34-98
` Applications in the food industry- Gums and mucilages
`have a variety of applications in the food industry.
`Different gums have different uses like water retention
`and stabilization (guar and locust bean gum), stabilizers
`for ice-cream, meat products and instant pudding
`(carrageenanas), dairy, confectionary and meat products
`(agar), confectionary, beverages, backed product, and
`sauces (gum arabic, tragacanth, pectins, alginates and
`xanthan gum).
` Pharmaceutical applications- Gums and mucilages have
`a variety of applications in pharmacy. They are used in
`medicine for their demulcent properties for cough
`suppression. They are ingredients of dental and other
`adhesives and can be used as bulk laxatives. These
`hydrophilic polymers are useful as tablet binders,
`disintegrants, emulsifiers, suspending agents, gelling
`agents, stabilizing agents, thickening agents, film
`forming agents in transdermal and periodontal films,
`buccal tablets as well as sustaining agents in matrix
`tablets and coating agents in microcapsules including
`those used for protein delivery.
` Various gums and mucilages with their common names,
`biological sources, family and applications are listed in
`
`IJPPR, Vol-6, Issue 4, December 2014- January 2015, 901-912
`
`Reference
`
`76
`77
`78
`
`79
`
`80-82
`
`83-85
`
`86-89
`
`90
`
`91
`92
`
`93-96
`
`97, 98
`
`Page905
`
`bean
`
`Locust
`gum
`Mucuna gum
`Okra gum
`
`Cerataniasiliqua
`
`Leguminoseae
`
`Mucunaflagillepes
`Hibiscus esculentus
`
`Papillionaceae
`Malvaceae
`
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` KINDERFARMS LLC. v. GENEXA INC.
` PGR2023-00051
`
`
`Page 5 of 12
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`Page906
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`Rohit Rajendra Bhosale et al. / Natural Gums and…
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`MHz to 300 GHz. On exposure to microwaves, the polar
`or charge particles tend to align themselves with electric
`field component of the microwaves which reverses its
`direction e.g. at the rate of 2.4 × 109/s at 2.45 GHz
`microwave frequency. As the charged or polar particles in
`a reaction medium fail to align themselves as fast as the
`direction of the electric field of microwaves changes,
`friction is created, which heated the medium.
`Chemical Modification of Polysaccharides
` Chemical crosslinking
`Chemical crosslinking of polysaccharide is a versatile
`method with good mechanical stability.
`the
`into
`During crosslinking counterions diffused
`polymeric
`and
`crosslinking
`agent
`reacts with
`polysaccharides
`forming
`either
`intermolecular or
`intramolecular linkages.
` Crosslinking by radical polymerization
` Crosslinking by addition reaction
` Crosslinking by condensation reaction
`Graft
`copolymerization of polysaccharides: Graft
`copolymers by definition, consists of a long sequence of
`one polymer with one or more branches of another
`polymer. With
`the help of preformed polymer
`(polysaccharide in case of grafted polysaccharides) the
`synthesis of graft copolymer process will start. The free
`radical sites will create on this preformed polymer with the
`help of external agent. The agent should be effective
`enough to create the required free radical sites, at the same
`time should not be too drastic to rupture the structural
`integrity of the preformed polymer chain. Once the free
`radical sites are formed on the polymer backbone, the
`monomer can get added up through the chain propagation
`step, leading to the formation of grafted chains.100
` Vinyl/acryl graft copolymerization
` Chemical initiating system
` Radically initiating system
`Other methods
` Ester and ether formation using saccharide oxygen
`nucleophiles, including enzymatic reactions and aspects
`of regioselectivity
` The introduction of heteroatomic nucleophiles into
`polysaccharide chains
` The oxidation of polysaccharides, including oxidative
`glycol cleavage, chemical oxidation of primary alcohols
`to carboxylic acids, and enzymatic oxidation of primary
`alcohols to aldehydes
` Reactions
`polysaccharides,
`of
`uronic-acid-based
`nucleophilic reactions of the amines of chitosan and the
`formation of unsaturated polysaccharide derivatives.101
`Many studies have been carried out in fields including food
`technology and pharmaceuticals using polysaccharides.
`The Literature reviles that the extensive effort have been
`made in pharmaceutical research laboratory for the
`development of excipient from natural polysaccharides.
`The Literature survey also reviles the use of various
`physical and chemical methods for modification of
`polysaccharides for improving its activity.
`Some of them are:121
`Basavaraj et al (2011) designed and characterized
`sustained release Aceclofenac matrix tablets containing
`
`tamarind seed polysaccharide. They extracted tamarind
`seed polysaccharide (TSP) from tamarind kernel powder
`and utilized it in the formulation of matrix tablets
`containing Aceclofenac by wet granulation technique and
`evaluated for its drug release characteristics. Granules
`were prepared and evaluated for loose bulk density, tapped
`bulk density, compressibility index and angle of repose,
`shows satisfactory results. Formulation was optimized on
`the basis of acceptable tablet properties (hardness,
`friability, drug content and weight variations), in vitro drug
`release and stability studies. All the formulations showed
`compliance with pharmacopieal standards. The in vitro
`release study of matrix tablets were carried out in
`phosphate buffer pH 7.4 for 12 hr. Among
`the
`formulations, they observed that F5 shows 98.062% better
`controlled release at the end of 12 hr. The results indicated
`that a decrease in release kinetics of the drug was observed
`by increasing the polymer concentration. The drug release
`of optimized formulations F-5 follows zero order kinetics
`and the mechanism was found to be diffusion coupled with
`erosion (non-Fickian diffusion/anomalous). The stability
`studies were carried out according to ICH guideline which
`indicates that the selected formulations were stable.
`Tushar Deshmukh et al (2011) evaluated the gum obtained
`from of Butea monosperma as a tablet binder employing
`ibuprofen as a model drug. The gum was isolated from
`bark of Butea monosperma Lam. Physicochemical
`characteristics
`of
`gum were
`studied. Different
`formulations of tablets using Butea monosperma gum were
`prepared by wet granulation method. The binder
`concentrations in the present tablet were 2, 4, 6, 8, 10 and
`12% w/v. Tablets were prepared and subjected for
`evaluation of hardness, friability, drug content uniformity.
`Preliminary evaluation of granules showed that, 1.75 to
`2.06 granule % friability, 30.11 to 33.82º angles of repose
`and 4.146 to 6.512 compressibility index %. Tablet
`hardness was found to be in the range of 2.52 to 4.86
`kg/cm2, 155 to 267 sec disintegration time and more than
`90.00% dissolution in 105 min. From their study, it can be
`concluded that B. monosperma gum at 8% w/v exhibited
`good binding properties comparable to that of 10% starch.
`Gum can be used as a binding agent for the preparation of
`tablets.
`Sandhya P et al (2010) in their work, evaluated mucilages
`obtained from Malva sylvestris and Pedalium murex as
`Suspending Agent. The purpose of their study was to
`search for a cheap and effective natural excipient that can
`be used as an effective alternative for the formulation of
`pharmaceutical suspensions. The suspending properties of