Zn treatment effects on biological potential of fennel bulbs as affected by in vitro digestion process

Abstract Zn treatment effects on the stability of polyphenols, MDA (malondialdehyde) content, antioxidant and lipoxygenase inhibition activities of two varieties of fennel bulbs were studied by using an in vitro gastrointestinal digestion model. Likewise, the effect of Zn on viability cells of E. coli was also performed. The results revealed that high amounts of total phenolic and flavonoid compounds were released during the digestion process, especially after the intestinal phase. Additionally, the antioxidant and lipoxygenase inhibitory activity were affected by the gastrointestinal digestion process and seems to be correlated with total phenol contents. On the other hand, the viability of E. coli was not affected by the activity of our tested bulbs during passage through the artificial digestion model, but the treated bulbs activity contribute relatively to the inhibition growth of bacteria. The survival of E. coli in fennel bulbs was challenged with simulated gastrointestinal fluids and the results showed that the E. coli strains, despite having experienced a viability reduction at the intestinal phase, were able to overcome the exposure to the gastrointestinal synthetic fluids. This E. coli ability reinforces the need for good hygienic measures to assure safe fresh produce, even for those that are rich in antibacterial compounds.

摘要 本研究采用体外胃肠道消化模型，探究了锌（Zn）处理对两个品种茴香球茎的多酚稳定性、丙二醛（MDA, malondialdehyde）含量、抗氧化活性以及脂氧合酶抑制活性的影响。同时，本研究还考察了锌处理对大肠杆菌（E. coli）细胞活力的影响。研究结果显示，在消化过程中，尤其是肠消化阶段，会释放出大量总酚与黄酮类化合物。此外，胃肠道消化过程会对抗氧化活性与脂氧合酶抑制活性产生影响，且该活性变化与总酚含量具有相关性。另一方面，受试茴香球茎的活性在经过人工胃肠道消化模型后，并未对大肠杆菌的细胞活力产生影响，但经锌处理的茴香球茎的活性可相对抑制细菌生长。本研究采用模拟胃肠道流体对茴香球茎内的大肠杆菌开展存活胁迫实验，结果显示，尽管大肠杆菌菌株在肠消化阶段出现了活力下降，但仍可耐受人工合成胃肠道流体的暴露环境。大肠杆菌的这一耐受能力进一步表明，即便对于富含抗菌成分的新鲜农产品，也需落实良好的卫生措施以保障食品安全。