Use of in vitro digestion method and theoretical calculations to evaluate the bioaccessibility of Al, Cd, Fe and Zn in lettuce and cole by inductively coupled plasma mass spectrometry

• Determination of total content of Al, Cd, Fe and Zn in lettuce and cole samples
• In vitro bioaccessibility for Al, Cd, Fe and Zn in lettuce and cole samples
• Determination of polyphenols in lettuce and cole
• Theoretical calculations explaining the results for bioaccessibility of minerals in lettuce and cole

Theoretical calculations of the binding energies of metal-polyphenols and metal-cellulose, as well as the hydration energies of metal-polyphenols were used to support the results obtained for the bioaccessibility of aluminium, cadmium, iron and zinc from four types of lettuce and one type of cole that were evaluated using an in vitro gastrointestinal digestion model and inductively coupled plasma-mass spectrometry. The bioaccessibility of Al found in the vegetables were less than 11% of the total Al content, whereas Cd exhibited average bioaccessibility of approximately 14% for the fresh samples and 41% considering the dried vegetables studied. However, the results indicated average bioaccessibility of 35% and 26% for Zn and average bioaccessibility of 19% and 21% for Fe in fresh and dried samples, respectively. The low bioaccessibility of Al is due to its strong binding with all of the vegetable components, whereas the low bioaccessibility of Fe and Zn are due to their interactions with phytates. Cd was observed to be the most bioaccessible element in the dried samples because of its weak interaction with other components in the vegetables.