Utilization of Plant-Based Wastes for a Sustainable Preparation of Xanthophyll Esters via Acid Anhydrides Using β‑Pinene as a Bio-Derived Solvent

A new valorization strategy for selected plant-based waste materials has been put forward. We have shown that avocado peels (fruit waste) and green leaves of Japanese knotweed (plant waste) are good sources of free xanthophylls such as antheraxanthin (9 mg/100 g dry weight) and lutein (106 mg/100 g dry weight), respectively, which can be converted into xanthophyll esters, a process inspired by nature to regulate the physicochemical properties of these bioactive species such as solubility and chemical stability. To this end, we developed the first environmentally friendly and economically viable synthetic platform and critically evaluated it by preparing 55 different xanthophyll esters (combining 5 model xanthophylls with 11 structurally and electronically distinct acid anhydrides). These esters were synthesized using β-pinene as a bio-derived solvent at ambient temperature and pressure with excellent selectivity (median 97%) and finally isolated in high yields (median 81%) and with high purities (median 97%). The integration of this technology with xanthophyll-containing wastes contributes to the zero-waste principle, and new valorization pathways for invasive alien plant species (such as Japanese knotweed) are particularly welcome as they help to control their rapid spread which causes great economic damage and loss of biodiversity around the globe.