Enhancement of aminophthalhydrazides chemiluminescence by N-beta-alanyl-L-histidine (L-carnosine)

L-Carnosine was found to be a potent enhancer of chemiluminescence from luminol, isoluminol, or N-aminobutyl-N-ethyl-isoluminol oxidized by H5IO6 (2 mmol/L in 11 mmol/L NaOH) or 20 mmol/L K3Fe(CN)6 + 10 mmol/L H2O2 in 100 mmol/L NaOH. Reproducible chemiluminescence enhancement was obtained with luminol and L-carnosine, each from six different vendors, isoluminol from two different vendors, and two different oxidizers. The magnitude of enhancement depended upon the source and concentration of L-carnosine, type and concentration of aminophthalhydrazide and choice and concentration of oxidizer. Excellent signal/noise and fold-enhancement were obtained for all three aminophthalhydrazides by including 10 mmol/L L-carnosine during K3Fe(CN)6 + H2O2 oxidation. L-Carnosine increased the sensitivity of detection of the three aminophthalhydrazides by 25-100-fold. A new combination of K3Fe(CN)6 + H2O2 concentration resulted in 20-30-fold more light emission from N-aminobutyl-N-ethyl-isoluminol in the presence of 10 mmol/L L-carnosine compared to chemiluminescence generated by two previously published concentrations of this oxidizer. L-Carnosine could further improve the sensitivity of chemiluminescent assays for factor XIIIa and transglutaminase.