Evaluation of dissolution profiles of alpha lipoic acid soft gelatin capsules and tablets
Alpha lipoic acid (ALA) has become a common ingredient in many commercially available supplements. The aim of the present work is to compare the dissolution profiles of the certain samples of ALA soft gelatin capsules and tablets (300mg and 600mg) commercially available from the local market. Fixed volumes of the dissolution medium were withdrawn at 15, 30, 45 and 60 minutes. Dissolution tests were performed on the USP Apparatus 2 (Dissolution tester ERWEKA DT 800; rotating speed 75 rpm at 37±0.5oC, 900 mL, distilled water). Also, the purpose of this work was to adapt and use the HPLC method proposed by Salem for the determination of the amount of the active ingredient released [1,2]. HPLC was performed with a mobile phase composed of 0.05M phosphate buffer pH 3.5:acetonitrile=650:350v/v, and peaks were detected at 330nm. Degassed and diluted samples were analysed on Zorbax Eclipse XDB-C18 column (250×4.6mm, 5µm), at 25oC and 1.5 mLmin-1 flow rate. The dissolved amounts of ALA in soft capsules and tablets at the end of testing were in the range of 12.9±2.8%- 18.6±1.9% and 85.2±7.6%- 90.6±4.9%, respectively. The results of dissolution studies are summarized in Figure 1. which show the percentage of ALA dissolved as a function of time. The results obtained in this study indicated problems in drug release from the investigated ALA soft gelatin capsules. According to the results obtained, we can presume differences in therapeutic response of the investigated ALA soft gelatin capsules and tablets.
References:  Salem H (2010) Chromatographia 72: 327–330.
 Kataoka H (1998)J Chromatogr B 717: 247–262.