Charge and hydrophobicity of casein peptides influence transepithelial transport and bioavailability.

Antioxidant casein peptides were separated by SP-Sephadex C-25 and C 18 columns. The transepithelial transport and bioavailability including the transport ratio and the remaining ratios of antioxidant activity (RRAA) of these peptide absorbates, were then investigated using a Caco-2 cell monolayer. The results indicate that both the negatively charged peptide fractions (CF1, CF2 and CF3) and the more hydrophilic fraction (HF1) were mainly transported via PepT1 and paracellular routes. The positively charged fractions (CF4 and CF5) and hydrophobic fractions (HF2, HF3 and HF4) were transported via PepT1 and transcytosis. The strongly negatively charged and more hydrophobic fractions showed a higher transport ratio, which ranged from 9.5 to 12.5%; however, the transport ratio of positively charged and hydrophilic fractions ranged from 4.0 to 8.5%. The positively charged and hydrophilic fractions showed a higher RRAA.