Analytical evaluation of the bioavailability of bioactive peptides

Some food components such as peptides and polyphenols are known to exhibit various physiological benefits by their oral intake. The functional food compounds must be absorbed and reached to their targeted tissues or organs to exert their biological functions. In many cases, however, the evidence of the intact absorption and accumulation at the site of action in vivo remains unclarified. Furthermore, considering that functional compounds are metabolized and degraded in vivo, it is essential to clarify their bioavailability as evidence for their functionality. However, the bioavailability of many components remains unclear because there are not enough analytical systems that can determine the bioavailability of food components. In this presentation, we introduce our developed analytical system based on mass spectrometry to provide high sensitive detection and visualization of absorbed peptides.  

　We developed a highly sensitive peptide detection system by using LC-MS/MS with the aid of various amine derivatives, such as 2,4,6-trinitrobenzene sulfonate (TNBS) derivatization and 3-aminopyridyl-N-hydroxysuccinimidyl carbamate (APDS). These analytical systems could show the intact absorption and pharmacokinetics of anti-atherosclerotic peptides, Trp-His. Moreover, it was demonstrated that Tyr-Pro could permeate blood brain barrier in mice brain and accumulate in the hypothalamus, hippocampus, and cortex.

  Then, we also developed a highly sensitive visualization method by using phytic acid-aided high sensitive MALDI-MS imaging technique. The method visualized the intact absorption process of peptides across rat intestinal membrane through peptide transporter 1. In addition, the specific localization of BBB transportable peptide, Tyr-Pro, at the hypothalamus, hippocampus, and cortex in mouse brain. Considering such brain availability of the peptide, we also clarified a memory-improving function of Tyr-Pro in SAMP8 mice.

 In conclusion, appropriate analytical systems are essential to evaluate the bioavailability of functional peptides in vivo. It must be critical evidence to validate their physiological benefits.