Esterification of Lutein from Japanese Knotweed Waste Gives a Range of Lutein Diester Products with Unique Chemical Stability (vol 10, pg 6072, 2022)

A valorization strategy for an aggravating type of plant waste is put to the test herein. It envisions the use of Japaneseknotweed green leaves as a sustainable source of free lutein, fromwhich bioactive diesters could be prepared as potential value-added products with improved properties. To this end, 13structurally distinct model lutein diesters were synthesized andthe relationships between their structure and stability weresystematically determined. The forced degradation data showthat the stability of a particular lutein diester may depend to a largeextent on the type of exposure (elevated temperature, light,oxidant, or acidic environment) and, more importantly, not everyesterification attempt necessarily leads to an enhancement oflutein's chemical stability. However, three branched and bulkyproducts???lutein di(2,2-dimethylpropanoate), lutein di(2-methylpropanoate), and lutein di(3-methylbutanoate)???proved to beparticularly relevant, as they consistently exhibited 1.5-21-fold higher stability compared to free lutein, regardless of the stressconditions used. Finally, we show that the Japanese knotweed plant matrix had a significant negative or positive effect on pigmentdegradation kinetics that could not be easily predicted. Thus, the proposed valorization strategy is quite feasible, but theesterification approach should be tailored to the intended use of a lutein diester