A new insight into the oxidative mechanism of caffeine and related methylxanthines in aprotic medium: May caffeine be really considered as an antioxidant?

Background: Antioxidant properties have been recently suggested for caffeine that seems showing protective effects against damages caused by oxidative stress. In particular, a HO% scavenging activity has been ascribed to caffeine. Even if the oxidation of caffeine has been widely studied, the antioxidant mechanism is still far to be understood. Methods: The electrochemical behavior of caffeine, theobromine and theophylline was studied in aprotic medium by cyclic voltammetry and electrolysis in UV–vis cell; a computational analysis of the molecular structures based on the Density Functional Theory was performed; the reactivity of all substrates towards lead dioxide, superoxide and galvinoxyl radical was followed by UV–vis spectrophotometry. Results: Results supported the mono-electronic oxidation of the C4]C5 bond for all substrates at high oxidation potentials, the electron-transfer process leading to a radical cation or a neutral radical according to the starting methylxanthine N7-substituted (caffeine and theobromine) or N7-unsubstituted (theophylline), respectively. A different following chemical fate might be predicted for the radical cation or the neutral radical. No interaction was evidenced towards the tested reactive oxygen species. Conclusions: No reactivity via H-atom transfer was evidenced for all studied compounds, suggesting that an antiradical activity should be excluded. Some reactivity only with strong oxidants could be predicted via electron- transfer. The acclaimed HO% scavenging activity should be interpreted in these terms. The study suggested that CAF might be hardly considered an antioxidant. General significance: Beyond the experimental methods used, the discussion of the present results might provide food for thought to the wide audience working on antioxidants

A method for the molecular classification of pollen for forensic purposes

Forensic palynology and the identification of pollen grains using DNA barcoding is an underutilised field in criminal investigations. Successful identification of pollen grains is used to establish links between an offender or body and location-­‐related crimes. The use of palynology in criminal investigations has been limited due to slow speed of identification, limited expert specialization and poor taxonomic resolution. To fill the gap, DNA barcoding overcomes these limitations by offering taxonomic resolution down to species in a faster, more accessible way. Despite this, there are technical applications that need to be addressed before DNA barcoding can be implemented as a laboratory standard for forensic palynology. This study aims to address these gaps, and highlight the need to make DNA barcoding more accessible in the future of forensic palynology