Acetylation of Gum from Stem Bark Grewia mollis juss. for use as a Disintegrant in Tablet Formulation
Keywords:
Bleaching, Characterization, Grewia gum (GG), Organoleptic properties, AcetylationAbstract
Introduction: Gums are polysaccharides of natural origin that have been used traditionally as binders in the formulation of tablets by wet granulation. Grewia polysaccharide gum as a natural resource could be used as an excipient in the pharmaceutical industry to reduce the costs of pharmaceutical products. It may provide a suitable alternative to the synthetic counterparts which are expensive and mostly imported.12 Interest in Grewia polysaccharide gum as a pharmaceutical excipient has been on for more than a decade now.13This growing interest is informed by the viscous property of the gum extracted from the inner stem bark of the Grewia mollis plant. 12
Aim: This research aimed at acetylating gum from stem bark of Grewia mollis Juss (GG) using acetic anhydride as the acetylating agent.
Methods: GG 75 g was mixed with acetic anhydride 139 ml (150 g, ρ = 1.08 g/mL) in a ratio of 1:2. Sodium hydroxide 5.0 % w/v was used as an oxidizing agent and the mixture was stirred for 2 – 3 mins. After which 50 g of the acetylated gum was sized reduced in a mortar and dispersed in 100 mL of water (distilled water), then bleached using 20 mL of sodium hypochlorite solution (10 % w/v) for 1 h to obtain the buff colour (light brownish yellow).
Results: The yields of the gums were found to be 58.5, 80.3, and 60.0 % for GG (Grewia Gum), AGM (Acetylated Grewia Gum), and BAGG (Bleached Acetylated Grewia Gum) respectively. The pH values for the gums were 4.83, 4.95, and 4.01 for GG, AGM, and BAGG respectively. The swelling capacities were 1.59 ± 0.00, 2.90 ± 0.01, and 2.80 ± 0.00 respectively for GG, AGM, and BAGG. Moisture contents were 0.54 ± 0.01, 0.13 ± 0.01, and 0.12 ± 0.01 for GG, AGM and BAGG respectively. The LD 50 values of both the native and derivatized gums were both greater than 5000 mg.
Discussion: These findings revealed that the product yields may be dependent on the species of Grewia processed as well as the processing conditions. Also, the difference in the yield between the AGM (80.3 % w/w) and BAGG (60.0 % w/w) was due to the lost for materials in the course of bleaching. The pH value of BAGG mucilage would be relatively unchanged if samples are stored at 25 o C to 45 o C, which is desirable for pharmaceutical excipients that may be subjected to elevated temperatures during processing, handling or storage. The BAGG samples are preferably stored in air-tight containers under low humidity. The swelling index of our studied BAGG powder was greater than that of Grewia venusta evaluated by Alobo and Arueya (2017) (2.80 ± 0.00 % vs. 1.7 ± 0.1%). This implies that BAGG-containing dosage forms exhibit relatively superior bioadhesive and sustained drug release properties.
Conclusion: The results of this study had been able to establish that chemical modification through acetylation of GG improved the physicochemical properties of the gum which invariably increases its emulsifying capacity that further increases its swelling index and solubility thereby opening prospects for extending the applications of the native gum.
