Purification of Free Lutein from Marigold Flowers by Liquid Chromatography

Marigold is a rich source of a Xanthophyll called lutein, which shows antioxidant and anti-cancer activities and is beneficial to eye health. This has led to various extraction and purification studies to obtain the high purity free lutein suitable for human applications. Liquid chromatography is extensively used to purify high value natural compounds because the process results in high purity products. The suitable mobile phase and stationary phase are the key factors to achieve high purity. In this work, chromatographic separation of lutein extracted from marigold flowers was investigated, using silica gel and mixture of hexane:ethyl acetate as a stationary and a mobile phase, respectively. Initially, the suitable composition of hexane:ethyl acetate was determined using a thin layer chromatography. Hexane:ethyl acetate mixture at 70:30 volume ratio was found to be an appropriate mobile phase for a normal phase chromatographic separation of free lutein. Preliminary experiments on a semi-preparative and a preparative column carried out at the mobile phase flow rate of 10 ml/min suggested that as high as 97.1 % purity free lutien could be obtained with a 60 % approximate yield. Moreover, since the separation by chromatography arises from the adsorption of free lutein onto silica gel, thus to better understand the process, a batch adsorption study was carried out to obtain the equilibrium adsorption data. The isotherm plotted from these data was found to be reasonably described by Langmuir adsorption model.