Native and pregelatinized starches of bitter yam as film formers for oral dissolving formulations

Abstract

Background: Oral dissolving films are portable dosage forms that consist of active pharmaceutical ingredients incorporated into film-forming polymers such as starch. Starches obtain optimum filmogenic properties by gelatinization and blending with other polymers. The high starch content of bitter yam (Dioscorea dumetorum Pax) gives it yet unexplored potential for orodispersible films.

Objectives: This study aimed to investigate the effect of pregelatinization on the physicochemical properties of bitter yam starch. Additionally, our objective was to evaluate the potential of both native starch (NS) and pregelatinized starch (PS), incorporated into polymer blends, as biopolymeric materials for use in orally dissolving films (ODFs).

Material and methods: Native and pregelatinized wild Dioscorea dumetorum Pax (bitter yam) starch were prepared and characterized using physicochemical, microscopic and rheological methods, Fourier-transform infrared spectroscopy, X-ray diffractometry (XRD), and differential scanning calorimetry (DSC). Oral dissolving films with varying hydroxylpropylmethyl cellulose (HPMC)-to-starch ratios (1:1, 1:2 and 2:1) were formulated and evaluated based on organoleptic properties, surface morphology, folding endurance, weight and thickness, pH, and disintegration time.

Results: Pregelatinization improved the swelling, solubility and hydration capacity of the starch. Although no changes were observed in the crystalline nature upon gelatinization, DSC analysis revealed remarkable changes in the thermal behavior of the NS after pregelatinization. Both NS and PS did not produce continuous films without HPMC. Flexibility of the starch increased with increasing HPMC concentration films, and PS-based films had higher folding endurance compared to NS films. Native starch-based films had smoother surfaces and higher thicknesses than PS films. All the starch films demonstrated disintegration times longer than 15 min, and slightly acidic pH values.

Conclusions: Pregelatinization of bitter yam starch, followed by blending with HPMC at a 2:1 ratio, resulted in the most effective oral film formulation. Further studies focusing on optimizing disintegration rates and pH would help confirm the suitability of this starch for use in ODF formulations.

Keywords: bitter yam; film formers; orodispersible films; starch pregelatinization.