Zeaxanthin is a carotenoid produced by plants and has been associated with protection of the photosynthetic machinery under light stress and, together with lutein, in protection of the central retina of the eye. Zeaxanthin levels in blood plasma have been negatively correlated to the development of AMD (age-related macular degeneration) (Gale et al, 2003). Under normal conditions, plants have a low content of zeaxanthin. The aim of this study was to increase the zeaxanthin content in green vegetables by post harvest treatments. Efficient conditions for activation of the endogenous enzyme system generating zeaxanthin was established and included incubation at low pH (2.5-5.5), with the membrane permeable acetic acid/acetate buffer at room temperature or above for 30 min or more. Typically more than 20-fold increase in zeaxanthin content was obtained for spinach, corn salad, parsley, basil, lemon balm and peas. For spinach up to 4 mg/100 g fresh weight of leaves were obtained. In consequence less amount of vegetables would be needed in the diet to provide the same amount of zeaxanthin for the eye. (C) 2010 Elsevier Ltd. All rights reserved.