Impact of Amylose-Amylopectin Ratio of Starches on the Mechanical Strength and Stability of Acetylsalicylic Acid Tablets

The two main components of starch — amylose and amylopectin, are responsible for its interaction with moisture. This study investigated how moisture sorption properties of the starches with different amylose-amylopectin ratio impacted tablet properties including drug stability. The starch samples were equilibrated to 33, 53, and 75% relative humidity (RH) and then assessed for tabletability, compactibility, and yield pressure. Effect of humidity on viscoelastic recovery was also evaluated. Tabletability and compactibility of high-amylose starch were better than that of high-amylopectin starch at 33 and 53% RH. However, at 75% RH, the reverse was observed.

In terms of yield pressure, high-amylose starch had lower yield pressure than high-amylopectin starch. High-amylose starch tablets also exhibited lower extent of viscoelastic recovery than high-amylopectin starch tablets. The variations in the tableting properties were found to be related to relative locality of the sorbed moisture. Degradation of acetylsalicylic acid in high-amylose starch tablets at 75% RH, 40°C was less than the tablets with high-amylopectin starch. This observation could be attributed to the greater amount of water molecules binding sites in high-amylose starch.

Furthermore, most of the sorbed moisture of high-amylose starch was internally absorbed moisture, therefore limiting the availability of diffusible sorbed moisture for degradation reaction. Findings from this study could provide better insights on the influence of amylose-amylopectin ratio on tableting properties and stability of moisture-sensitive drugs. This is of particular importance as starch is a common excipient in solid dosage forms.

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Materials

Native maize starches of different amylose-amylopectin ratio were used: high-amylose maize starch (amylose ≥ 88%; maize starch amylo N-400, Roquette, France) and high-amylopectin maize starch (amylopectin ≥ 88%; waxy maize starch N-200, Roquette, France) (34, 35). Acetylsalicylic acid (ASA; USP grade, Bengbu Bayi Pharmaceuticals, China) was used as the model drug. The presence of ester functional group makes ASA susceptible to degradation by hydrolysis.

Magnesium chloride hexahydrate (MgCl₂∙6H₂O; Merck Chemicals, Germany), magnesium nitrate hexahydrate (Mg(NO₃)₂∙6H₂O; Merck Chemicals, Germany), and sodium chloride (NaCl; Merck Chemicals, Germany) were used for maintaining RH conditions of 33, 53, and 75% RH, respectively (36). For evaluation of ASA degradation, the following solvents were used — acetonitrile (HPLC Grade, Fisher Chemical, USA), ortho-phosphoric acid (Merck Chemicals, Germany), and purified water.

Veronica, N., Liew, C.V. & Heng, P.W.S. Impact of Amylose-Amylopectin Ratio of Starches on the Mechanical Strength and Stability of Acetylsalicylic Acid Tablets. AAPS PharmSciTech 23, 118 (2022). https://doi.org/10.1208/s12249-022-02266-0

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