Effect of simulated adult and infant digestion on the antioxidant and cellular protective effects of Camellia sinensis and Aspalathus linearis tea

Background: Many South Africans have a poor antioxidant status and fermented Camellia sinensis (BT) and Aspalathus linearis (RT) teas that are widely consumed by adults and infants is a possible source of antioxidants which can address this deficiency by protecting cells and tissue against reactive oxygen species damage. Objective: The aim of this study was to determine the extent to which antioxidant properties of these teas are affected by adult and infant gastrointestinal digestion. Methods: Water extracts of BT (n = 4) and RT (n = 3) were prepared and were subjected to adult and infant simulated in vitro digestion. For pH controls, stomach (SD) and subsequent duodenal digestion (SDD) fractions the total polyphenolic (TPC) and flavonoid (TFC) content was determined. Antioxidant activity was determined with the DPPH, TEAC and ORAC assays. The NO scavenging ability of each fraction as well as the cellular antioxidant activity in the Caco-2 cell line using the DCHF-DA assay was evaluated. Results: With adult and infant digestion these antioxidant properties in the SD and SDD phase of digestion were increased, unchanged or reduced due to pH dependent extraction or degradation of polyphenolics and/or the biotransformation of flavanols and other flavonoids. TFC of BT remained relatively stable with infant and adult digestion, as well as with infant digested RT. Significant losses in antioxidant activity as determined by the DPPH and ORAC assays of BT and RT were found following complete adult and infant digestion, whereas TEAC assay did not show such a great loss following digestion. NO scavenging assay and DCFH-DA were less affected by infant digestion than by adult digestion. Following infant digestion of BT and RT, cellular protection against oxidative damage was 94.97% and 83.99%, respectively. For adult digestion, cellular protection was 83.15% and 71.71% for complete digested BT and RT, respectively. The RSC of tea was calculated and it was found that one cup BT and two cups RT provided the equivalent of 200 mg vitamin C for adults. One cup of both teas provided more than the equivalent of 30 mg vitamin C needed for infants. GIT enzymes may serve as a protein matrix that protects polyphenols against pH driven degradation or quench radicals. Conclusion: Adult and infant digests of fermented BT with in most instances was found to have better antioxidant properties than RT. As a significant amount of antioxidant activity remained following digestion, both RT and BT may assist in the prevention and management of infections and chronic diseases. However BT contains caffeine which makes RT, the better choice for infants, children and caffeine sensitive adults.