Electrospray ionization mass spectrometry analysis of polyisoprenoid alcohols via Li+ cationization

Direct analysis of polyisoprenoids by electrospray ionization mass spectrometry (ESI–MS) often produces poor results requiring off-line time and sample-consuming derivatization techniques. We describe a simple ESI–MS approach for the direct analysis of polyisoprenoids using several dolichols and polyprenols with different chain sizes as proof-of-principle cases. Lithium iodide is used to promote cationization by intense formation of [M + Li]+ adducts. Thus, detection of polyisoprenoids with mass determination can be performed with high sensitivity (limit of detection [LOD] ∼100 ρM), whereas characteristic collision-induced dissociations observed for both dolichols and polyprenols permit investigation of their structure. Using ESI(Li+)–MS and ESI(Li+)–MS/MS analysis, we screened for polyprenol products of an octaprenyl pyrophosphate synthase of Plasmodium falciparum and dolichols in a complex mixture of compounds produced by Leishmania amazonensis and P. falciparum.