Spinach (Spinacia oleracea L.) flavonoids are hydrolyzed during digestion and their bioaccessibility is under stronger genetic control than raw material content

Authors: Dzakovich, Michael; TAK, ALVIN - Baylor College Of Medicine; LE, ELAINE - Baylor College Of Medicine; DANG, RACHEL - Rice University; REDAN, BENJAMIN - Consultant; DUBROW, GEOFFREY - Consultant

Submitted to: Foods
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/9/2025
Publication Date: 12/15/2025
Citation: Dzakovich, M.P., Tak, A., Le, E., Dang, R., Redan, B., Dubrow, G.A. 2025. Spinach (Spinacia oleracea L.) flavonoids are hydrolyzed during digestion and their bioaccessibility is under stronger genetic control than raw material content. Foods. 14(24). Article 4314. https://doi.org/10.3390/foods14244314.
DOI: https://doi.org/10.3390/foods14244314

Interpretive Summary: Spinach contains natural compounds called flavonoids that are believed to contribute to its health benefits. However, little is known about how much these compounds vary between different types of spinach, what controls their production, and how much of them can actually be absorbed by the body after digestion. Without this knowledge, it is difficult for plant breeders and nutrition scientists to improve spinach’s health-promoting qualities. We measured 39 flavonoids from 30 varieties of spinach grown under controlled growing conditions. We found that flavonoid levels are strongly influenced by the environment and that spinach has at least two different parts of the pathways that makes these compounds. We also showed that while the main flavonoids are fairly consistent, minor flavonoids can distinguish traditional and hybrid varieties. Importantly, we discovered that the ability of the body to access flavonoids (bioaccessibility) is more strongly linked to genetics than their raw levels in the plant, and that many flavonoids change form during digestion. This work reveals how spinach's flavonoids vary, how they are controlled, and how they behave during digestion. By showing that bioaccessibility is more heritable than raw content, our findings highlight a new and more effective target for plant breeders Ultimately, this knowledge paves the way for developing spinach varieties with altered health benefits.

Technical Abstract: Spinach (Spinacia oleracea L.) is a commonly consumed crop with a diverse array of unique flavonoids. These molecules likely contribute to the health benefits associated with spinach consumption. However, little is known about the genetic diversity of these molecules, their molecular regulation, and their bioaccessibility. We assembled a diversity panel of 30 F1 and open pollinated spinach accessions and cultivated them under controlled conditions over two periods. Quantification of 39 flavonoids revealed that their concentration is largely influenced by environmental factors and at least two divergent branches in the flavonoid biosynthesis pathway may exist. Despite largely similar trends in the amounts of major flavonoids, open pollinated and F1 varieties of spinach could be distinguished based on the concentrations of minor flavonoid species. Broad sense heritability estimates for absolute bioaccessibility accounted for more genetic variation than raw material content, suggesting that this trait is preferable for breeders seeking to alter the phytochemical profile of spinach. Lastly, we found that several spinach flavonoids are unstable under digestive conditions, as shown by the proportion of aglycones rising from 0.1% to approximately 15% of total flavonoids after digestion. Together, these data suggest that spinach flavonoid biosynthesis and bioaccessibility is complex and contextualizes how these molecules may behave in vivo.