Untargeted metabolite analysis of healthy and Huanglongbing-infected orange leaves by CE-DAD.

Huanglongbing (HLB) is considered the most destructive bacterial citrus disease worldwide. Early detection of HLB is crucial for minimizing its spread. CE was used for the discovery of potential biomarkers for HLB. Optimization of extraction and separation allowed resolving 24 compounds of which 6 were present in significantly higher (p<0.05) concentrations in HLB-infected samples collected monthly for 6 months during the 2007-2008 season. Three of these compounds were identified by mobility and UV spectra as hesperidin, naringenin, and quercetin with mean increase in concentration of 154, 555, and 467%, respectively, above that in healthy leaves. Results support the potential of CE-DAD for untargeted plant metabolomic analysis. CZE, NACE, and MEEKC were compared for metabolic differentiation of healthy and HLB-infected citrus leaves. CZE in a semi-aqueous BGE solution consisting of 8.5 mM of sodium borate (pH 9.3), 15% ACN, and 9% 1-butanol yielded the best peak separation with detection at 190 nm.