Synthesis, characterization and evaluation of carboxymethylated Okra gum as suspending agent in metronidazole suspension

Abstract

Modification of natural polymers can alter their physicochemical properties and consequently improve functionality. Modification should be undertaken such that the natural polymers do not lose their biological properties. The purpose of this study was to investigate the suspending properties of plain and modified Okra gum in metronidazole suspension. Okra gum was extracted from the pods of Abelmoschus esculentus and modified by Carboxymethylation. Nine (9) batches of metronidazole suspensions were formulated with 0.5%, 1% and 1.5% of native Okra gum (Batches KB1-KB3), 0.5%, 1% and 1.5% of tragacanth (KB4-KB6) and 0.5%, 1% and 1.5% of carboxymethyl-Okra gum (KB7- KB9). The formulated suspensions were evaluated using these parameters: sedimentation volume, redispersibility, pH and viscosity and compared with tragacanth used as standard gum. Experimental results revealed that the swelling index of plain and modified okra gum were 260 and 525% respectively giving a 2-fold increase after modification; while the viscosity of plain and modified okra gum were 150 and 15 mPas respectively giving a 10-fold decrease in viscosity after modification. Suspensions were acidic with pH range of 3.83-4.76. The suspensions formulated with carboxymethyl-okra gum had better redispersibility profile with lesser redispersion number ranging from 6-12, as against 9-18 for native okra gum and 7-16 for tragacanth. The study demonstrates that both plain and carboxymethyl-okra gum have good suspending properties and compared favorably with the standard gum, tragacanth. However, modification of okra gum by arboxymethylation, improved functionality in terms of the swelling index and redispersibility which could result in more stable flocculated pharmaceutical suspension systems.

Keywords: Suspension, Carboxymethylation, Okra gum, Metronidazole