1. Investigación

In a preliminary study pyroglutamate showed to be over 10 times increased in some lyophilised coffees with respect to brewed or filtered coffees, and probably that increase is related to some stage of the industrial process. Pyroglutamate is known to have a number of remarkable cognitive enhancing effects, which could be also related to the properties of coffee traditionally associated to caffeine. Pyroglutamate improves memory and learning and has anti-anxiety effects in rats. Therefore, a method has been developed and validated for the simultaneous determination of caffeine and pyroglutamate in coffee by capillary electrophoresis. Separation conditions employed MECK conditions with 50 mM borate buffer at pH 9.5 with 130 mM SDS. The applied potential was 10 kV and detection was performed at 200 nm. Afterwards, 10 soluble coffees from the market were measured and caffeine and pyroglutamate levels were compared. Those coffees with higher pyroglutamate with or without caffeine were preliminarily tested for sedative/stimulant properties and cognition enhancing effects in mice. The most relevant finding was a partial reversal of scopolamine-induced amnesia in the passive avoidance paradigm after oral administration of one coffee.

An in-capillary sample preconcentration strategy based on solid phase extraction (SPE) technology coupled with capillary electrophoresis (CE) has been developed taking advantage of both techniques (SPE and CE). An in-line frit-free preconcentration device for capillary electrophoresis containing MCX beads, obtained from the corresponding Waters OASIS® cartridges, was prepared. The retention of the particles was based on the relative diameters of the particles, carefully selected, and the capillaries. An experimental preconcentration factor of 100 was found for the system. Conditions were optimised for 3-nitrotyrosine measurement in rat urine being 4.4 M spiked in the urine the lowest value detectable.