Evaluation of polysaccharides from Malvaceae as sustainable excipients for sustained-release oral tablets

Polysaccharides continue to attract interest as renewable and biodegradable alternatives to conventional semi synthetic tableting excipients in sustained release tablets. Building upon previous investigations on polysaccharides extracted from the Malvaceae family, this study focuses on a polysaccharide extracted from Baobab fruit as a potential sustainable tableting excipient. Polysaccharides were extracted from Nigerian baobab fruit pulp by hot water extraction at pH6 and ethanol precipitation. The extracted baobab polysaccharide (BP) consisted of predominantly linear xylogalacturonans (containing between ~30-40% galacturonic acid) and significant proportions of neutral sugars. Comparable uronic acid contents are reported for other polysaccharides from the Malvaceae family investigated as tableting excipients, such as okra (47–57 %) [1] and grewia gum (19–35%) [2], suggesting broad compositional similarities but notable differences in ratios of neutral to acidic monosaccharides.

The amorphous BP powder was characterised and compacted into tablets with microcrystalline cellulose and theophylline as a model drug. An increase in BP concentration (from 10% to 57.5%) enhanced the tablets' mechanical strength and reduced their porosity (from 11% to 9%). Dissolution studies revealed pH dependent release. At pH 1.2, tablets with a higher BP content (30–57.5%) demonstrated sustained release over a 4h period. Conversely, at pH 6.8, increasing the BP content promoted a burst release. This behaviour of strong acid stability and erosion dominated release at higher pH, is likely controlled by BP’s xylogalacturonan rich, weakly acidic structure, which forms a gel in acidic media and rapidly erodes in a basic environment. This performance places BP in an interesting position relative to other Malvaceae polysaccharides. Grewia gum produces hard compacts and maintains sustained release in both acidic and neutral media [3] and okra polysaccharides, with their higher uronic acid content, typically form a stable swollen gel on the tablet surface that slows drug release [4].

Overall, these findings establish BP as a promising, sustainable excipient with pH dependent release characteristics. The chemical composition and structural differences among Malvaceae polysaccharides underpin their distinct release behaviours with BP’s weakly acidic structure favoring pH responsive erosion, grewia’s low uronic acid and high degree of branching promoting mechanical reinforcement and okra’s balanced composition favouring a stable surface gel formation. This highlights the potential and functional diversity of polysaccharides extracted from the Malvaceae family in the development of environmentally responsible sustained release oral dosage forms.

References: [1] Alba et al (2015) Food Hydrocoll. 43,726-735 [2] Alba et al (2021) Food Hydrocoll. 118, 106749. [3] Nep et al (2015) Int. J. Pharm, 496, 689-698 [4] Ghori et al (2014) Food Hydrocoll. 42, 342-347
Relevant Conference Theme: Role of hydrocolloids in pharmaceuticals and health/personal care products

Presentation Type: Oral presentation