ACETYLATION OF GUM FROM STEM BARK GREWIA MOLLIS JUSS. FOR USE AS A DISINTEGRANT IN TABLET FORMULATION

Abstract

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.