At the end of the annual horticultural production cycle of greenhouse-grown crops, large quantities of residual biomass are discarded. Here, we propose a new value chain to utilize horticultural leaf biomass for the extraction of secondary metabolites. To increase the secondary metabolite content of leaves, greenhouse-grown crop plants were exposed to low-cost abiotic stress treatments after the last fruit harvest. As proof of concept, we evaluated the production of the flavonoid rutin in tomato plants subjected to nitrogen deficiency. In an interdisciplinary approach, we observed the steady accumulation of rutin in young plants under nitrogen deficiency, tested the applicability of nitrogen deficiency in a commercial-like greenhouse, developed a high efficiency extraction for rutin, and evaluated the acceptance of the proposed value chain by its key actors economically. On the basis of the positive interdisciplinary evaluation, we identified opportunities and challenges for the successful establishment of horticultural leaf biomass as a novel source for secondary metabolites.

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Extraction procedures for plant‐based secondary metabolites are mainly influenced by choice of solvent, particle size and solvent to feed ratio. For developing an extraction protocol design‐of‐experiments or model‐based approaches have widely been used. Botanical aspects such as the influence of side compounds are less investigated. Either for analytical or preparative purposes, knowledge of the underlying extraction mechanisms is required to improve the process development. In this work, we demonstrate the mechanism of accessibility limitation of rutin by side compounds depending on the solvent to feed ratio. Extraction yields of target and side compounds are analyzed to derive correlations. The role of side compounds as limiting factors for target compound accessibility is demonstrated by performing two extraction steps using three different plant species. The maximum extraction yield of rutin is reached using a solvent to feed ratio of at least 300 for all three investigated plant species, while side compounds in liquid state generally affect the extractability of rutin. Phosphatidylcholines are identified as possible accessibility‐limiting compounds. In conclusion, the yields of target and side compounds strongly depend on the solvent to feed ratio, while side compounds cover the target compound in dry matter, reducing its accessibility.