Natural polymers, gums and mucilages as efficacious green emissaries of essential therapeutics

. The emergence of natural polymers like gums and mucilages in drug delivery systems has curbed the rampant use of the synthetic materials for therapeutic purposes. Natural excipients offered advantages such as non-toxicity, less cost and abundantly availablity. Aqueous solubility of natural excipients plays an important role in their selection for designing immediate, controlled or sustained release formulations. This review article provides an overview of natural gum, polymers and mucilages as excipients in dosage forms as well as novel drug delivery systems. These recent investigations have provided ample evidences that these natural gums and mucilages like Gellan Gum, Gum Acacia, and Locust bean gum could efficaciously deliver therapeutics to the diseased site without exerting any significant adverse effects on the normal cells. Henceforth these natural polymers are endowed with the ability to function as like green emissaries for the transport of essential therapeutic agents which in turn will help in restraining the belligerence of different grave diseases like cancer.

MOL2NET, 2020, 6, ISSN: 2624-5078 6 http://sciforum.net/conference/mol2net-06 prolonged the drug release more extensive as compared to that containing single polymer. By utilizing release retarding properties of gum, controlled release profile was achieved in delivery of pentoxifylline [14]. Patel et al. [15] evaluate gum and guar gum for formulation of floating dosage form for dipyridamole. The prepared tablets had desired buoyancy characteristics. Hence gum could be use in floating drug delivery formulations.Gohel et al. [16] explored the use of blend containing gum and hydroxypropylmethyl cellulose for development of modified release drug delivery system of diltiazem HCl. The drug release kinetics for tablets followed Hixson-Crowell equation and showed drug release for 12 hrs.
Tamarind seed polysaccharide. It is a galactoxyloglucan. Sumathi et al. [17] isolated tamarind seed polysaccharide from tamarind kernel powder and studied the sustained release behavior of both watersoluble and water-insoluble drugs from tamarind seed polysaccharide.Acetaminophen, caffeine, and theophylline were used as water-soluble drug whereas salicylic acid and indomethacin as waterinsoluble drug. It was founded that the mechanism of release of soluble drugs was anomalous whereas water-insoluble drug showed zero order release behavior.
Gellan gum. It is an exocellular polysaccharide secreted by Pseudomonas elodea. This gum had been investigated for pharmaceutical applications such as tablet disintegrant, binder, gelling agent and controlled release polymer [18]. Smith et al. [19] prepared enteric coated dosage form by utilizing gellan gum, sodium alginate and hypromellose. The dosage form remined intact for about two hours in HCl (pH 1.2) but when placed in buffer (pH 6.8) it was ruptured. Thus, it was concluded that these natural polymers can be used in the formulation of delayed release dosage forms. Babu et al. [18] evaluated the suitability of gellan gum macrobeads for development of gastroretentive controlled delivery of amoxicillin. They prepared gellan gum beads by using ionotropic gelation with calcium ions.The macrobeads provided release which was fitted to diffusion model. Hence, gellan gum could be used in controlled drug delivery formulation. Emeje et al. [20] prepared matrix tablets of metronidazole using gellan gum in different concentrations and studied its release profile. It was concluded from the study that optimum concentration of gum (0.2%w/w) showed most effective as a MOL2NET, 2020, 6, ISSN: 2624-5078 7 http://sciforum.net/conference/mol2net-06 disintegrant. The use of gellan gum as a controlled release carrier in the formulation of gastro-floating matrix tablets has been done by Elmowafy et al. [21]. In a study, an attempt to design bi-layer tablet of metoclopramide HCl and ibuprofen, the use of gellan gum as disintegrant was done [22]. Narkar et al. [23] used gellan gum in preparation of stomach-specific controlled release mucoadhesive drug delivery system. They employed amoxicillin trihydrate as model drug. The in vitro dissolution study showed that drug release upto 7 hrs in a controlled manner and following the Peppas model. From the results of both in vitro and in vivo mucoadhesivity study, it was revealed that gellan gum beads possess good mucoadhesivity even after 7 hrs. Singh et al. [24] investigatedthe suitability of gellan beads for the development of colon specific controlled drug delivery system. Gellan beads to deliver azathioprine were prepared as a potential colonic delivery system by ionotropic gelation and were coated with Eudragit S-100. Gum releases drug in controlled manner. Thus, it was suggested the use of gellan gum as a carrier for controlled colonic specific drug delivery systems.

Resin. It is a clear, pale yellow to dark amber thermoplastic resin that present in oleoresins of tree
Pinus soxburghi and Pinus toeda belong to family Pinaceae. Nande et al. [25] prepared diclofenac sodium loaded microspheres using PEGylated rosin derivative. Microspheres were formulated by emulsion solvent evaporation method. In vitro dissolution study showed that the release follows Higuchi equation. It was reported that fickian diffusion was the mechanism of drug release. They suggested that PEGylated derivatives of rosin could be used for preparing microspheres to obtain sustained release of drug. In another study, Nande et al. [26] evaluate potential use of PEGylated derivatives of resin as film formers, which showed sustained release. Fulzele et al. [27] prepared sustained release microcapsules of diclofenac sodium by employing polymerized resin. They use polymerized rosin as wall-forming agent. Formulated microcapsules showed sustained release of drug for about 10 hrs. In vitro dissolution study showed that drug release from microcapsules follow Higuchiorder release pattern. Pathak et al. [28] prepared tablets of aspirin using rosin and its esters as hydrophobic matrix materials for controlled drug delivery. The tablets were formulated by wet granulation technique. Formulations had good mechanical strength and showed hardness greater than 6 MOL2NET, 2020, 6, ISSN: 2624-5078 8 http://sciforum.net/conference/mol2net-06 kg/cm2. Disintegration time for tablets was greater than 150 min. Thus, resin act as a hydrophobic matrix forming agent for development of controlled drug delivery systems.
Grewia gum. Grewia gum is a biodegradable hydrophilic gum obtained from Grewia mollis. It is mainly used in formulations of controlled release dosage forms. As gum is hydrophilic so when it comes in contact with aqueous medium it swells and forms a viscous dispersion. Ogaji et al. [29] evaluated grewia gum as a suspending agent in liquid oral preparations. They formulated suspension of ibuprofen using grewia gum. They found that grewia gum showed minimal changes in viscosity on storage. Hence, grewia gum could be utilized as suspending agent in suspension formulations.
Carrageenan. It is obtained from seaweeds of class Rhodophyceae. Red seaweeds including Iradaea aminariodes, Chondrus cripus, Euchema spinosum are the major sources. Picker et al. [30] and Hariharan et al. [31] suggested carrageenan use as excipient in controlled-release tablets. Bonferoni et al. [32] prepared carrageenan-diltiazem complex and evaluate it as a excipient used in controlledrelease formulations. In their study they found that there was the highest crushing strength and the slowest drug release, when the finest sieve fraction of complex was employed. They also suggested that drug release mechanism was surface dissolution or erosion. The prepared tablets had high crushing strength. They suggested that the studied carrangeenans showed good compatibility and controlled release behavior. Picker et al. [33] studied the drug release from ternary mixture composed of kappacarrageenan, microcrystalline cellulose and theophylline monohydrate. The results showed different drug release mechanisms from ternary mixture based on the concentration of kappa-carrageenan used.
When proportion of kappa carrageenan about 20% v/v was used, there was fast release of drug whereas when 30% v/v was used, itshowed zero-order kinetics. This was due to swelling of tablets made of ternary mixture. Bani-Jaber et al. [34] prepared interpolymeric complex of carrageenan and chitosan and evaluated its influence on drug release. It was concluded that this complex was able to sustain drug release from polymeric matrix. Ghanam et al. [35] proposed the use of carrageenan pellets for the preparation of multiparticulate tablets which showed modified drug release. In another study evaluation of carrageenans (Gelcarin GP-379 and Viscarin GP-209) as a carrier for the preparation of MOL2NET, 2020, 6, ISSN: 2624-5078 9 http://sciforum.net/conference/mol2net-06 controlled-release drug delivery system was carried out. Tablets containing both carrageenans in equal proportion showed zero-order release profile [31].
Terminalia catappa gum. Kumar et al. [36] examined terminalia catappa gum as vehicle for oral sustained release tablets. Dextromethorphan hydrobromide was selected as a model drug for their study. Dextromethorphan hydrobromide tablet composed of terminalia catappa gum prepared by direct compression method. Sustained release of drug was demonstrated in phosphate buffer (pH 6.8).
Formulation showed sustained release of more than 8 hrs. Hence, terminalia catappa gum is a promising basis in the design of controlled drug delivery system.
Mimosa pudica seed mucilage. Singh et al. [37] examined the sustained-release properties of mimosa pudica seed mucilage on diclofenac sodium. Tablets were prepared by wet granulation method. Results showed that as the increase concentration of mucilage in fortmulation decreases the release of drug from tablets. Higuchi square root release kinetics was followed by formulations and showing diffusion release mechanism when high amount of mucilage was utilized whereas showed both matrix erosion and diffusion mechanisms for formulations composed of less amount of mucilage. Ahuja et al. [38] prepared buccal discs of fluconazole by using mimosa pudica seed mucilage as bucoadhesive. The discs were prepared by employing direct compression method. The results revealed that polymer showed bioadhesion time of 10 hrs and more than 85% release of drug in 10 hrs.
Pectin. It is methoxyester of pectic acid. Plant cell walls are the major source of pectin. The different sources of pectin include sunflower, orange, lemon, carrot, mango, guava and papaya. It has more stability in acidic media. In one study, it has been suggested that pectin in combination with gelatine can be used as an encapsulating excipient to provide sustained release. Turkoglu et al. [39] used pectin-hydroxypropylmethyl cellulose compression coat on 5-aminosalicylic acidcore tablets for colonic delivery. The study confirmed that selective delivery of 5-aminosalicylic acid to colon could be achieved utilizing pectin-hydroxypropylmethyl cellulose as a carrier in the form of a compression coating. Rao et al. [40] evaluated use of pectin in combination with hydroxypropylmethyl cellulose and hydroxyethyle cellulose for colon drug delivery. Naproxen tablet matrices prepared by using MOL2NET, 2020, 6, ISSN: 2624-5078 10 http://sciforum.net/conference/mol2net-06 different proportion of polymers. Tablet coating was done by ethyl cellulose and cellulose acetate phthalate. Results showed that pectin-hydroxyethyl cellulose base coat could be used as carrier to deliver naproxen to colon. Mura et al. [41] investigated a new colonic drug delivery system using pectin matrix system with Eudragit S100 coating.
Alginate. Sodium alginate is a natural polysaccharide isolated from the brown seaweed. Alginates offer utilizations in dosage forms including microspheres, beads, liposomes, tablets, buccal films.
Sodium alginate act as thickening agent and hence, use in preparation of pastes and creams. It is also employed as disintegrating agent and binder in tablet formulations. Miyazaki et al. [42] prepared bioadhesive tablets of ketoprofen using mixture of chitosan and sodium alginate in different ratios (4:1, 1:1 and 1:4). It was found from the study that 1:4 ratio of chitosan and alginate served to be the optimized oral sustained release tablet of ketoprofen. Liew et al. [43] studied the release behavior of drug from sodium alginate based formulations. According to them, alginate particle size, affect the extent of burst release and also sodium alginate based matrices sustained the drug release upto 8 hrs.
Gum acacia. It is obtained from stems of tree Acacia Arabica. It is water soluble and form viscous gel in water.In studies it was showed that gum acacia could be used as binder in tablets. In combination with gelatn, gum acacia can be used as encapsulating agent in preparation of microspheres. Dash et al. [44] prepared microspheres and microcapsules of tolnaftate by using gelatine-acacia coacervation method. Stability study of formulation was performed and found that the drug was stable in microspheres and microcapsules formulation for about 6 months. Lu et al. [45] suggested the use of gum Arabic in preparation of oral controlled drug delivery. They prepared naproxen osmotic tablets. In their tablets they use gum arabic as osmotic agent. The effect of gum Arabic on drug release was studied. The optimal formulation deliver drug by following zero order for 12 hrs.
Locust bean gum. Malik et al. [46] evaluated locust bean gum as superdisintegrants. They fabricated orodispersible tablets of nimesulide, by using locust bean gum. Results of their study concluded that tablet formulation containing 10% locust bean gum showed 13 seconds disintegration time.
Khaya gum. It is naturally occurring hydrophilic polysaccharide obtained from tree, Khaya grandifiola belonging to family Meliaceae. In studies khaya gum used as binding agent in tablets, for drug targeting and controlled release has been reported. Odeku et al. [48] evaluated khaya gum as a controlled release agent in tablet formulations. Paracetamol tablets were formulated by employing direct compression method. From their studies, it was found that khaya gum provide controlled release of drug for 5 hr. Also combination of khaya gum and hydroxypropylmethylcellulose showed zeroorder time independent release kinetics. Thus, tablets matrices composed of khaya gum could be utilized to obtain sustain release. In another study Odeku et al. [49] studied khaya and albizia gum coating for drug targeting to the colon. Odeku et al. [50] evaluated khaya gum as binder in tablets.
Paracetamol was used as model drug. All fabricated tablets possess friability value less than 1%.
Tablet formulations containing khaya gum as binder had lower tensile strength values.