Evaluation of Eudragit® Retard Polymers for the Microencapsulation of Alpha-Lipoic Acid

Author(s): Tiziana M.G. Pecora, Teresa Musumeci, Lucrezia Musumeci, Massimo Fresta, Rosario Pignatello.

Journal Name: Current Drug Delivery

Volume 13 , Issue 7 , 2016

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Abstract:

Background: Microencapsulation of natural antioxidants in polymeric systems represents a possible strategy for improving the oral bioavailability of compounds that are otherwise poorly soluble.

Objective: α-lipoic acid (ALA) was microencapsulated with polymethacrylate polymers (blends at various ratios of Eudragit® RS100 and RL100 resins).

Method: Microspheres were produced by solvent displacement of an ethanol cosolution of ALA and polymers; the microsuspensions were then freeze-dried, using trehalose as a cryoprotector. Microspheres were characterized in the solid state for micromeritic properties and drug loading, as well as by infrared spectroscopy, powder X-ray diffractometry and differential scanning calorimetry. The antioxidant activity of free and encapsulated ALA was assessed by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay.

Results: In vitro release studies, performed in simulated gastric (pH 1.2) and intestinal fluid (pH 6.8), showed that, depending on polymer composition and drug-to-polymer ratio, ALA release can be slowed down, compared to the dissolution pattern of the free drug. Solid-state characterization confirmed the chemical stability of ALA in the microspheres, suggesting that ALA did not develop strong interactions with the polymer and was present in an amorphous or a disordered-crystalline state within the polymer network. As indicated by the DPPH assay, the microencapsulation of ALA in Eudragit® Retard matrices did not alter its antioxidant activity.

Conclusion: ALA was effectively encapsulated in Eudragit® Retard matrices, showing a chemical stability up to 6 months at room conditions and at 40°C. Moreover, since the drug maintained its antioxidant activity in vitro, the potential application of these microparticulate systems for oral administration would deserve further studies.

Keywords: Antioxidant activity, coevaporates, DPPH assay, Eudragit® Retard, lipoic acid, microencapsulation, polymers.

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Article Details

VOLUME: 13
ISSUE: 7
Year: 2016
Page: [1165 - 1175]
Pages: 11
DOI: 10.2174/1567201812666151016095342

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