Green Sequential Extraction of Carotenoids and Coproducts from Invasive Alien Plants and Non-Edible Agricultural Residues

Industrial carotenoid supply is still largely based on dedicated crops, such as marigold, which require arable land and agricultural inputs that can compete with staple food production. This study explores invasive alien plants and nonedible agricultural residues as alternative carotenoid sources and develops a green, sequential extraction strategy for their valorization. Eleven model plant materials were screened, revealing carotenoid contents up to 126 mg/100 g dry weight (DW), with lutein predominating and occurring mainly in the free, potentially more bioavailable form. Using Japanese knotweed leaves as a model matrix, maceration with stirring under mild conditions (25 °C) was combined with a hydrophobic natural deep eutectic solvent (NaDES) consisting of thymol/coumarin (1:1; NaDES4). NaDES4 proved particularly effective, providing higher lutein and β-carotene recoveries than acetone under optimized maceration (84 ± 6 vs 56 ± 7 mg lutein/100 g DW and 27 ± 2 vs 20 ± 2 mg β-carotene/100 g DW). A sequence-controlled extraction scheme using water, ethanol, and acetone or NaDES4 enabled integrated recovery of carotenoids, carbohydrates, and polyphenols and increased cumulative carotenoid recovery by up to 90% when nonpolar steps preceded polar steps. Safety screening showed no pesticides above the limits of quantification, but PAH levels in 11 of 22 hydrophobic extracts exceeded EU limits and depended strongly on the collection site, underscoring the need for location-aware sourcing. Taken together, these results demonstrate that invasive plants and vegetable residues can complement dedicated carotenoid crops and support the development of green, multiproduct utilization routes for underexploited plant biomass.