Exploring the role of genetic diversity on spinach flavonoid bioaccessibility

Authors: DANG, RACHEL - Rice University; LE, ELAINE - Children'S Nutrition Research Center (CNRC); TAK, ALVIN - Children'S Nutrition Research Center (CNRC); DUBROW, GEOFF - Food And Drug Administration(FDA); Dzakovich, Michael

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 12/15/2023
Publication Date: N/A
Citation: N/A

Interpretive Summary: Spinach is a popular leafy green in the U.S. Along with many nutrients, spinach contains an array of unique compounds known as flavonoids that are associated with good health. Flavonoids similar to the ones found in spinach have been shown to reduce inflammation or lower the risk of developing certain cancers. However, there is not a solid understanding of how efficiently flavonoids are released from spinach and made available for absorption during digestion (bioaccessibility). To spinach flavonoid bioaccessibility, we grew an array of commonly consumed spinach varieties and determined the release of over 40 different flavonoids using a simulated digestion. We found that there was a range of flavonoid concentrations in the spinach varieties we studied and their rate of release during digestion varied substantially. We also found that genetics more strongly influenced the bioaccessibility of flavonoids to a greater degree than the starting content in the leaves. Unknown environmental factors also accounted for a large portion of both raw material content and bioaccessibility. Overall, our study is one of the first to define the bioaccessibility of spinach flavonoids. By understanding this, we can learn more about how spinach affects our health. But, we still need more studies to see if what we found in the lab aligns with what happens in real life when people consume spinach.

Technical Abstract: Spinach is one of the most consumed leafy greens in the United States and contains a high concentration of flavonoids only found in this vegetable. These compounds and related phytochemicals exhibit antioxidative, anti-inflammatory, and anti-carcinogenic properties in vitro. However, the bioaccessibility of these compounds (the efficiency they are released from food and made available for absorption) is poorly defined. Understanding how genetics controls spinach flavonoid biosynthesis and bioaccessibility is critical for addressing hypotheses about their role in human health and nutrition. Using publicly available sequence data, we selected 30 accessions of spinach representing both wild and cultivated germplasm. Spinach accessions were cultivated in a randomized complete block design over three growing periods. Harvested samples were processed into a model food, in vitro digested, and analyzed for 42 species of flavonoids using a novel liquid chromatography tandem mass spectrometry (LC-MS/MS) approach. Bioaccessible aqueous fractions were semi-purified using solid phase extraction and flavonoids were quantified using LC-MS/MS to determine absolute and relative bioaccessibility. These data indicate that spinach flavonoids in model foods exhibited a diverse range of concentrations (exceeding an order of magnitude for some analytes). Moreover, bioaccessibility of spinach flavonoids was more strongly controlled by genetics than the initial starting content in leaves suggesting that this trait is more heritability than raw material concentration.Undefined environmental factors appear to partially determine the concentration and bioaccessibility of spinach flavonoids. These data represent one of the first attempts to comprehensively quantify flavonoids produced in spinach and link their concentration and bioaccessibility to plant genetic background. Characterized spinach germplasm can be used to test future hypotheses about specific flavonoid profiles and their effects on various health outcomes. Additional studies are needed to determine if data collected from in vitro digestion approaches matches animal or human clinical estimates of bioavailability.