Martins Leiziani Gnatkowski, Khalil Najeh Maissar, Mainardes Rubiana Mara
Department of Pharmacy, Universidade Estadual do Centro-Oeste/UNICENTRO, Rua Simeão Camargo Varela de Sá 03, 85040-080 Guarapuava, PR, Brazil.
J Pharm Anal. 2017 Dec;7(6):388-393. doi: 10.1016/j.jpha.2017.05.007. Epub 2017 May 20.
Melatonin is a natural hormone and with the advancement of age its production declines and thereby may result in some neurological disorders. Exogenous administration of melatonin has been suggested as a neuroprotective agent. Due to its low oral bioavailability, the loading of melatonin in polymeric nanoparticles could be an important tool to effectively use exogenous melatonin. The quantification of the incorporated drug within polymeric nanoparticles is an important step in nanoparticles characterization. An analytical method using high performance liquid chromatography equipped with photodiode array detector (HPLC-PDA) was developed and validated for melatonin determination in poly (lactic acid) nanoparticles obtained by a single emulsion-solvent evaporation technique. The melatonin in vitro release profile also was determined by the HPLC method. Mobile phase consisted of acetonitrile: water (65:35, v/v) pumped at a flow rate of 0.9 mL/min, in the isocratic mode and PDA detector was set at 220 nm. The method was validated in terms of the selectivity, linearity, precision, accuracy, robustness, limits of detection and quantification. Analytical curve was linear over the concentration range of 10-100 μg/mL, and limits of detection and quantification were 25.9 ng/mL and 78.7 ng/mL, respectively. The mean recovery for melatonin was 100.47% (RSD = 1.25%, = 9). In the intra- and inter-assay, the coefficient of variation was less than 2%. Robustness was proved performing changes in mobile phase, column temperature and flow rate. The method was suitable for the determination of melatonin encapsulation efficiency in poly(lactic acid) nanoparticles and for the evaluation of melatonin in vitro release profile.
褪黑素是一种天然激素，随着年龄的增长，其分泌量会下降，从而可能导致一些神经紊乱。外源性给予褪黑素已被认为是一种神经保护剂。由于其口服生物利用度低，将褪黑素负载于聚合物纳米粒中可能是有效利用外源性褪黑素的重要手段。聚合物纳米粒中所含药物的定量是纳米粒表征的重要一步。建立了一种使用配备光电二极管阵列检测器的高效液相色谱法（HPLC-PDA），并对其进行了验证，用于测定通过单乳液-溶剂蒸发技术制备的聚乳酸纳米粒中的褪黑素。褪黑素的体外释放曲线也通过HPLC法测定。流动相由乙腈：水（65:35，v/v）组成，以0.9 mL/min的流速等度泵入，PDA检测器设置在220 nm。该方法在选择性、线性、精密度、准确度、稳健性、检测限和定量限方面进行了验证。分析曲线在10-100 μg/mL的浓度范围内呈线性，检测限和定量限分别为25.9 ng/mL和78.7 ng/mL。褪黑素的平均回收率为100.47%（RSD = 1.25%，n = 9）。在批内和批间分析中，变异系数小于2%。通过改变流动相、柱温和流速证明了方法的稳健性。该方法适用于测定聚乳酸纳米粒中褪黑素的包封率以及评估褪黑素的体外释放曲线。
