Lutein in selected Canadian crops and agri-food processing by-products and purification by high-speed counter-current chromatography

Abstract

This study mainly focused on lutein content in several selected crops grown in southern Ontario, Canada. Marigold flower, a good rotation crop for the control of nematodes in tobacco fields was found to contain 0.77% lutein (after saponification, on dry basis). A high-speed counter-current chromatography (HSCCC) method using a two-phase solvent system consisting of hexane-ethanol-water (6:4.5:1.5, v/v/v) was developed for the purification of lutein from the saponification mixture of marigold flower extract. The purity of lutein prepared using this HSCCC method was 97%. Free lutein was found to be the predominant form in three squash varieties, and it was mostly found in the peel rather than the commonly consumed flesh. Sweet Mamma, Buttercup and Pepper squash varieties contained 25.4, 18.4 and 30.1 mg/100 g fresh weigh (FW) of lutein in the peels, respectively. These concentrations were significantly higher than that in spinach and kale (3.7 and 12.3 mg/100 g FW). β-Carotene was found most in the peel of Sweet Mamma squash at 13.6 mg/100 g FW, whereas it was below 2 mg/100 g FW in all other samples. Cooking increased extractable free lutein by 22–65% in squash peels. Lutein in Yukon Gold potato was at ca. 0.4 mg/100 g FW. Certain Yukon Gold was also found to contain violaxanthin (0.35 mg/100 g FW). Structures of lutein, β-carotene and violaxanthin were identified by LC-atmospheric pressure chemical ionization MS in positive ion mode, and by comparing the retention time and UV–vis spectral data with standards. Results from this study suggest the selected crops and agri-food industrial processing by-products of these can be a good source of free lutein.