University of São Paulo: Technology developed at USP has the potential to reduce the degradation of natural antioxidants
Mora, strawberry, açaí, grape, acerola, red cabbage and eggplant are some of the foods rich in anthocyanins – natural compounds with antioxidant power that, combined with a healthy lifestyle and diet, bring many benefits to human health. The problem is that less than 5% of anthocyanins keep their molecular structure intact until the end of the digestive process. Most of them end up degrading before being absorbed by the cells. The good news is that a study by the Food Research Center (FoRC) paved the way to change this picture, by providing greater stability to the structure of the molecule.
“To reduce the degradation of anthocyanins, which occurs during digestion, mainly at intestinal pH and by the action of intestinal bacteria, we developed capsules on a nanometer scale. These nanocapsules cover the structure of anthocyanins, increasing chemical stability both during storage and during human digestion”, explains nutritionist Thiécla Katiane Osvaldt Rosales, author of the research. She is responsible for developing the methodology, which has been patented and published in three journals: Food Hydrocolloids , Antioxidants and Colloids and Surfaces B: Biointerfaces. Other articles with the research results are under review. The work is the result of his doctorate, carried out under the guidance of pharmacist-biochemist João Paulo Fabi, professor at the Faculty of Pharmaceutical Sciences (FCF) at USP and a member of the FoRC.
The nanocapsules are made from natural compounds: pectin, a polysaccharide extracted from citrus, and lysozyme, a protein found in egg whites. In vitro tests were carried out , with electron and scanning microscopy, to evaluate the technology in four aspects: stability, physical and chemical protection capacity, absorption capacity by cells and toxicity.
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One of the tests applied was InfoGest, an internationally recognized protocol that simulates human gastrointestinal digestion, taking into account several variables, such as body temperature, peristaltic movements, enzyme action and physiological pH. “In this test, we found that approximately 42% of the initial anthocyanins had been protected from degradation, that is, at the end of the simulated digestion, they either kept their molecular structures intact within the nanocapsules or had been gradually released for cellular absorption. In the control group, with free anthocyanins, less than 13% of the initial molecules were in these same conditions, in vitro ”, says Thiécla.
In the research, it was also found that the cells were able to absorb the nanocapsules and remained alive, that is, there was no apparent toxicity. “The number of live cells was similar to the untreated control group. This shows that nanocapsules are potentially safe”, says Thiécla.
The assays were carried out with the aid of fluorescent markers, which showed not only the absorption of the nanoparticles but also the non-alteration of the proportions between living and dead cells: “When the cell absorbed the nanoencapsulated anthocyanin, the green color inside the cell structure was visualized through the microscope”, he exemplifies. Both the two-dimensional model, with cells adhered to the culture plate, and the three-dimensional model, with cells in spheroids, were used, mimicking the intestinal microenvironment.
The next step of the research, already at the postdoctoral level, will be to carry out in vivo tests . This stage of the research will be carried out at the Institute for Energy and Nuclear Research (Ipen), in partnership with the FoRC. “Ipen has equipment with which it will be possible to confirm the data already studied”, he says. “We need to know if nanoparticles will remain stable in a living organism. In addition, we will be able to monitor in vivo, also with markers, how the nanoparticles are absorbed and their bioavailability [use in metabolism] ”, he adds.
promising applications
The final objective of the research is to transfer technology with a view to the development of food supplements with antioxidant action, for adjuvant treatments of diseases. Another possible application would be the production of natural dyes. “Anthocyanins are responsible for imparting a wide range of colors to flowers, fruits and leaves, stems and roots of plants – from carmine red to violet, pink and blue. What prevents this application is precisely the instability of the compounds, as the maintenance of colors depends directly on their structural integrity.”
According to Thiécla, the technology is affordable – it does not require sophisticated or expensive equipment. In addition, the natural compounds of the raw material occur in abundance. Pectin, for example, is widely found in residues from the food industry, such as citrus and apple peels, for example.