What is "meso-zeaxanthin"

Meso-zeaxanthin (3R,3´S-zeaxanthin, see Figure 1) is a xanthophyll carotenoid (as it contains oxygen and hydrocarbons), and is one of the three stereoisomers of zeaxanthin. Of the three stereoisomers, meso-zeaxanthin is the second most abundant in nature (after 3R,3´R-zeaxanthin, which is produced by plants and algae. To date, meso-zeaxanthin has been identified in specific tissues of marine organisms, and more importantly, meso-zeaxanthin has been identified in the macula lutea (from Latin, macula = "spot" and lutea = "yellow") of the human retina.