A colorimetric method and a capillary electrophoresis procedure were developed for quantifying histidylleucine and hippurate, respectively. The colorimetric method is sensitive (extinction coefficient = 7.5 mM-1 cm-1) and reproducible (CV = 1.7%, n = 5), which is based on a selective chromogenic reaction for histidylleucine (λmax = 390 nm) using o-phthalaldehyde. For samples containing unusually high levels of histidine and/or histidyl peptides, the separation-based approach is preferable. The capillary electrophoresis method makes use of an in-capillary microextraction technique; complicated samples can be measured in less than 4 min without pretreatment. Protocols using both methods to measure angiotensin converting enzyme inhibitory activity were proposed.
All Science Journal Classification (ASJC) codes
- Molecular Biology
- Cell Biology