Abstract
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.
Highlights
Carotenoids are natural pigments, and owing to their antioxidant, anticancer,[1,2] antidiabetic, and anti-inflammatory activities,[1,2] they have numerous beneficial effects on human health
The main aim of this study was to identify some prevalent plant-based waste materials which are rich in free xanthophylls and use them to produce xanthophyll esters as a new valorization strategy for this type of waste
One monohydroxyxanthophyll (β-cryptoxanthin) and four dihydroxyxanthophylls readily found in many plants were used to create a library of products xanthophylls esterified with various carboxylic acids: aromatic,functionalized,branched, andsaturated short- and long-chain aliphatic carboxylic acids (Table S1)
Summary
Carotenoids are natural pigments, and owing to their antioxidant, anticancer,[1,2] antidiabetic, and anti-inflammatory activities,[1,2] they have numerous beneficial effects on human health. Inedible parts of fresh fruits and vegetables (e.g., the skin, peels, trimmings, and kernels) represent major horticultural losses and wastes (23−28%), but they are a rich source of many valuable bioactive compounds such as polyphenols, oils, enzymes, vitamins, and many others, including carotenoids.[6] There is a continuous need to create and invent new products with value-added applications stemming from alternative bioresources as a means to build a pathway to a sustainable future Another type of plant waste material originates from the mechanical control of invasive alien plant species, which threaten natural ecosystems through the loss of biodiversity. With its biomass yield reaching up to 15.9 tons per hectare,[9] accumulation of harvested Japanese knotweed waste is substantial and calls for new alternative uses
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