Characterization of Grewia Gum, a Potential Pharmaceutical Excipient

Grewia gum was extracted from the inner stem bark of Grewia mollis and characterized by several techniques such as gas chromatography (GC), gel permeation chromatography (GPC), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and thermogravimetric analysis of the extracted sample. Spectroscopic techniques such as x-ray photoelectron spectroscopy (XPS), fourier-transformed infrared (FT-IR), solid-state nuclear magnetic resonance (NMR), and 1H and 13C NMR techniques were also used to characterize the gum. The results showed that grewia gum is a typically amorphous polysaccharide gum containing glucose, rhamnose, galactose, arabinose and xylose as neutral sugars. It has an average molecular weight of 5925 kDa expressed as the pullulan equivalent. The gum slowly hydrated in water, dispersing and swelling to form a highly viscous dispersion exhibiting pseudoplastic flow behaviour. The polysaccharide gum is thermally stable and may have application as stabilizer or suspending agent in foods, cosmetics and in pharmaceuticals. It may have application as a binder or sustained-release polymer matrix in tablets or granulations

Grewia polysaccharide as a pharmaceutical excipient in matrix tablets

Matrix-based tablets using different concentrations of grewia gum, and the model drug ibuprofen, were prepared using a wet granulation technique. Similar formulations were also prepared using HPMC, guar gum or ethyl cellulose as the polymer matrix. In addition to tablet properties, swelling and erosion of tablets and kinetics of drug release were also investigated. In vitro drug release studies, in phosphate buffer (pH 7.2) using USP type II apparatus, revealed that grewia gum at concentrations of 16%, 32% and 48% can sustain the release of ibuprofen tablets for up to 24 hours. Release profiles were similar to those tablets containing ethyl cellulose as the matrix former. Swelling and erosion of grewia gum matrices occurred simultaneously, and ibuprofen release was by anomalous diffusion in accordance with the Korsmeyer-Peppas model. There was evidence suggesting synergism between grewia gum and guar gum in sustaining the release of ibuprofen from tablets when used in the ratio 2:1. Grewia gum may therefore prove a useful excipient, when used on its own, or in combination with other polymers, to modify drug release

Physicochemical characterization of polysaccharides extracted from sesame leaves: a potential matrix for sustained release tablets

Purpose In the developing world the pharmaceutical sector depends heavily on imported raw materials which elevate the cost of medicines beyond the reach of the majority of the local population; despite often being rich in renewable sources which could be used as excipients. In this study we have extracted and characterised a largely undeveloped polysaccharide, sesamum gum, with a view to application as an alternative pharmaceutical excipient. Methods Polysaccharide from the leaves of Sesamum indicum was extracted by maceration in distilled water followed by precipitation in absolute ethanol. The material was oven dried and milled to a particle size of 250 m. The resulting material was characterized using X-ray diffractometry (XRD), Fourier transform infra-red spectroscopy, differential scanning calorimetry and thermogravimetric analysis. The total carbohydrate content, protein content and intrinsic viscosity of the extracted gum were determined according to standard protocols. Constituent sugar analysis of the material was determined by high performance anion exchange chromatography after hydrolysis of the samples using 2M trifluoroacetic acid for 3 hours. Compaction studies were carried out using a Testometric materials testing machine and data analysed by Heckel analysis. Results The polysaccharide gum had a total carbohydrate content of 98.1% and protein content of 1.7%. XRD spectra were typical of an amorphous material with a maximum decomposition temperature of 266.7 °C. Intrinsic viscosity was determined to be approximately 3.31 and 4.40 dl/g in 0.1 M NaCl and deionized water respectively. Dispersions of the polysaccharide are viscoelastic and exhibit shear-thinning behaviour. The polysaccharide contains fucose (0.1%), rhamnose (1.1%), arabinose (2.8%), galactose (48.9%), glucose (2.7%), mannose (6.8%) and xylose (33.6%) as neutral sugars, and glucuronic acid (3.0%) and galacturonic acid (1.1%) as acid sugars. Heckel analysis indicates that sesamum consolidates plastically having mean yield pressure of 131.45 MPa. Conclusion Sesamum polysaccharide is typically amorphous with a low content of uronic acids. Results suggest it is a thermally stable, high molecular weight polymer which exhibits shear-thinning behaviour in the hydrated form. The polymer in the dry state is a highly compactable material which has the potential to be exploited as a matrix former in sustained release tablets

Eudragit E100 and Polysaccharide Polymer Blends as Matrices for Modified-Release Drug Delivery I: Physicomechanical Properties

Purpose: To compare the effects of two states of polymer/polymer blending (dry and aqueous/lyophilized) on the physicomechanical properties of tablets, containing blends of locust bean gum (LB) with Eudragit® E100 (E100) and sodium carboxymethylcellulose (SCMC) as matrices.Methods: LB, SCMC and E100 were blended in their dry (as purchased) state or modified by aqueous blending and subsequent lyophilization, prior to use as matrices in tablets. The polymer blends were characterized by infra-red spectroscopy (FTIR), flow and compressibility tests, as well as physicomechanical analysis of their tablets.Results: No significant variations were noticeable in the FTIR peaks of the individual polymers in the dry and the aqueous/lyophilized states. Aqueous/lyophilized blending of the polymers resulted in better flow properties. The aqueous/lyophilized matrices were denser with improved mechanical strength and the tablets were harder than those produced from dry blended polymers.Conclusion: Dry blending of LB with E100 and SCMC greatly improved the physicomechanical properties of the tablets. This was further enhanced by aqueous/lyophilized blending.Keywords: Drug delivery, Polymer blend, Eudragit, Locust bean gum, Levodopa, Sodium carboxymethylcellulose, Matrix, Physicomechanical propertie

Eudragit E100 and Polysaccharide Polymer Blends as Matrices for Modified-Release Drug Delivery II: Swelling and Release Studies

Purpose: To compare the effects of two states of polymer/polymer blending (dry and aqueous/lyophilized) of locust bean gum with Eudragit® E100 and sodium carboxymethylcellulose on swelling and drug (levodopa) release from their tablet matrices.Methods: Sodium carboxymethylcellulose (SCMC), Eudragit® (E100) and locust bean (LB) were blended in their dry (as purchased) state or modified by aqueous blending and subsequent lyophilization prior to use as tablet matrices. The tablets were evaluated for swelling and in vitro drug release. Furthermore, in vivo absorption was predicted from the in vitro release data by convolution method.Results: E100 matrices exhibited little or no swelling while the matrices of SCMC and LB and their blends exhibited a degree of swelling > 180 %. Aqueous blending and lyophilization modulated the rate of release from matrices formulated with LB, SCMC and their polymer/polymer blends. Drug release profiles of the lyophilized polymer/polymer blends matrices were dissimilar to those of the dry polymer/polymer blends. Formulations F1aq, F2aq and F3aq exhibited fairly uniform absorption in the first 8 h, indicating the possibility of producing a steady delivery of drug.Conclusion: Polymer blending of LB, SCMC and E100, achieved by aqueous blending and lyophilization, enhances the performance of the matrices thereby exhibiting controlled levodopa release with no burst effect and the tablets retained their three-dimensional network.Keywords: Controlled release, Drug delivery, Eudragit, Locust bean, Levodopa, Matrix, Polymer blend, Sodium carboxymethylcellulos

Characterization of grewia gum, a potential pharmaceutical excipient

Grewia gum was extracted from the inner stem bark of Grewia mollis and characterized by several techniques such as gas chromatography (GC), gel permeation chromatography (GPC), scanning electron microscopy (SEM), dilute solution viscometry, differential scanning calorimetry (DSC) and thermogrametric analysis of the extracted samples. Spectroscopic techniques such as x-ray photoelectron spectroscopy (XPS), fourier-transformed infrared (FT-IR), solid-state nuclear magnetic resonance (NMR), and 1H and 13C NMR techniques were also used to characterize the gum. The results showed that grewia gum is a typically amorphous polysaccharide gum containing glucose, rhamnose, galactose, arabinose and xylose as neutral sugars. It has an intrinsic viscosity of 48.36 ± 0.37 dl/g and an average molecular weight of 5925 kDa expressed as the pullulan equivalent. The gum slowly hydrated in water, dispersing and swelling to form a highly viscous dispersion exhibiting pseudoplastic flow behaviour. The polysaccharide gum is thermally stable and may have application as stabilizer or suspending agent in foods, cosmetics and in pharmaceuticals. It may have application as a binder or sustained-release polymer matrix in tablets or granulations

Evaluation of grewia polysaccharide gum as a suspending agent

Grewia polysaccharide gum was extracted from the inner stem bark of Grewia mollis, thereupon drying was achieved by air‐drying (ADGG) or freeze‐drying (FDGG). The suspending ability of grewia gum was compared to that of xanthan (XAN), sodium carboxymethylcellulose (SCMC) and acacia gum (ACA) in ibuprofen suspension. The physical stability of the ibuprofen suspension formulations, containing the suspending agents at a range of concentrations, was assessed by appearance and pourability, viscosity and rheology, sedimentation volume ratio, redispersibility, degree of flocculation, zeta potential and microbial load. The ADGG and FDGG‐containing formulations exhibited pseudoplastic flow with a viscosity‐imparting ability superior to ACA and SCMC‐containing formulations, but not XAN, at all concentrations. ADGG‐containing formulations (1.0 %w/v) remained fully suspended for over 42 days while all the other formulations sedimented within 24 hours except XAN‐containing formulations. The FDGG and ADGG‐containing formulations were more easily redispersed than SCMC‐containing formulations and exhibited a higher degree of flocculation at 0.75 %w/v than ACA or SCMC‐containing formulations. The zeta potential of XAN, ADGG or FDGG‐containing suspension formulations were more negative than ‐30 mV and therefore more stable than SCMC or ACA‐containing suspension formulations (zeta potentials of < ‐23 mV). All suspension formulations showed evidence of microbial growth on storage. ADGG or FDGG may provide a suitable alternative as suspending agent in pharmaceutical oral suspensions

Grewia Gum 2: Mucoadhesive Properties of Compacts and Gels

Purpose: To compare the mucoadhesive performance of grewia polysaccharide gum with those of guar gum, carboxymethylcellulose, hydroxypropyl methylcellulose and carbopol 971P. Methods: Grewia polysaccharide gum compacts or gels as well as those of guar gum, carboxymethylcellulose, hydroxypropyl methylcellulose or carbopol 971P were prepared. Texturometric and tensile analysis of the polymer gels and compacts were carried out using a software-controlled penetrometre, TA.XTPlus texture analyzer. The polymer gels were evaluated for hardness, stickiness, work of cohesion and work of adhesion. Furthermore, the detachment force of the polymer compacts from a mucin substrate was evaluated. Results: The work of adhesion of guar gels was significantly greater than that of grewia gels (p < 0.001) but the latter showed a significantly greater work of adhesion than carboxymethylcellulose gels (p < 0.05) and hydroxypropyl methylcellulose gels (p < 0.001). However, the work of cohesion for grewia/mucin gel mixture was significantly greater (p < 0.001) than those of carboxymethylcellulose/mucin, hydroxypropyl methylcellulose/mucin and carbopol 971P/mucin gel blends. The difference between the mucoadhesive performance of grewia compacts and those of hydroxypropyl methylcellulose and carbopol 971P compacts was insignificant (p > 0.05). Conclusion: Grewia polysaccharide gum demonstrated good mucoadhesive properties, comparable to those of carbopol 971P, carboxymethylcellulose, guar gum and hydroxypropyl methylcellulose, and therefore, should be suitable for the formulation of retentive drug delivery devices

Grewia Gum 1: Some Mechanical and Swelling Properties of Compact and Film

Purpose: To study the mechanical and dynamic swelling properties of grewia gum, evaluate its compression behaviour and determine the effect of drying methods on its properties. Methods: Compacts (500 mg) of both freeze-dried and air-dried grewia gum were separately prepared by compression on a potassium bromide (KBr) press at different pressures and subjected to Heckel analysis. Swelling studies were performed using 200 mg compacts of the gum (freeze-dried or air-dried) compressed on a KBr press. The mechanical properties of the films of the gum prepared by casting 1 % dispersions of the gum were evaluated using Hounsfield tensiometer. The mechanical properties of grewia gum films were compared with films of pullulan and guar gum which were similarly prepared. The effect of temperature on the water uptake of the compacts was studied and the data subjected to Schott’s analysis. Results: Drying conditions had no effect on the yield pressure of the gum compacts as both air-dried and freeze-dried fractions had a yield pressure of 322.6 MPa. The plots based on Schott’s equation for the grewia gum samples showed that both samples (freeze-dried and air-dried) exhibited long swelling times. Grewia gum film had a tensile strength of 19.22±3.61 MPa which was similar to that of pullulan films (p > 0.05). It had an elastic modulus of 2.13±0.12 N/mm2 which was significantly lower (p < 0.05) than those of pullulan and guar gum with elastic moduli of 3.33±0.00 and 2.86±0.00 N/mm2, respectively. Conclusion: The type of drying method used does not have any effect on the degree of plasticity of grewia gum compacts. Grewia gum obtained by either drying method exhibited extended swelling duration. Matrix tablet formulations of the gum will likely swell slowly and promote sustained release of drug