Impact of fermentation on the bioaccessibility and bioactivity of xanthophylls (lutein and zeaxanthin) in selected fruits and vegetables: an in vitro Caco-2 study.

Lutein and zeaxanthin are carotenoids that play a significant role in maintaining eye health and must be obtained from dietary sources, as humans cannot synthesise them de novo. However, their concentrations in foods are generally very low. This study evaluates the role of fermentation in enhancing the bioaccessibility of xanthophylls in twelve commonly consumed fruits and vegetables. In addition, it investigates the cellular uptake and bioactivity of raw and fermented kale and corn, which contain detectable levels of both lutein and zeaxanthin. The Lutein and zeaxanthin contents increased by 30-50% in fermented vegetables after five days of spontaneous fermentation. Similarly, cellular uptake of those compounds increased by 35% and 38% in kale and corn, respectively. Fermented kale and corn also demonstrated a 45-50% reduction in cytokine production in response to induced inflammatory and oxidative stress in Caco-2 cells, indicating enhanced anti-inflammatory and antioxidant properties. Full-length 16S rRNA sequencing revealed that Leuconostoc mesenteroides, Lactiplantibacillus plantarum, Lactococcus lactis and Weissella confusa were the dominant bacteria in fermented corn and kale. The consistent increase in lutein and zeaxanthin observed during the controlled fermentation of kale and corn using bacteria isolated from their respective spontaneously fermented samples further supports the beneficial role of spontaneous and controlled fermentation in enhancing xanthophylls in plant foods.