Analysis of free-radical scavenging of Yerba Mate (Ilex paraguriensis) using electron spin resonance and radical-induced DNA damage.

Mate (MT) is a popular South American beverage that has been used as a traditional medicine for centuries, spurring recent interest in its nutraceutical properties. MT is prepared as an infusion of leaves from the Yerba Mate (llex paraguriensis) tree. MT has been reported to have antioxidant properties in vitro and in vivo, but these have not been fully characterized in terms of effects against specific radicals. Accordingly, we examined the antioxidant effects of an MT infusion against hydroxyl and superoxide radicals in both chemical and cell culture assays. MT infusions were prepared at 3.10 g/L in boiling water and diluted to experimental dilutions from this stock. Electron spin resonance (ESR) experiments indicated that MT scavenged hydroxyl radicals (produced via the Fenton reaction) and superoxide radicals (produced via the xanthine/xanthine oxidase enzymatic reaction) at all concentrations tested (P < 0.05). Further controls indicated that superoxide radical scavenging was not due to xanthine oxidase inhibition. MT scavenged hydroxyl radicals and decreased cellular oxygen consumption in a dose-dependent manner in Cr(VI)-stimulated RAW 264.7 cells, based on ESR and oxygraph measurements (P < 0.05). Similarly, MT also inhibited hydroxyl-radical-induced lipid peroxidation and DNA damage in a dose-dependent manner in RAW 264.7 cells, based on malondialdehyde and Comet assay data (P < 0.05). This study indicates that MT possesses potent antioxidant effects against hydroxyl and superoxide radicals in both chemical and cell culture systems, as well as DNA-protective properties. These data further clarify the reported antioxidant effects of Yerba Mate infusions.

Biochemical adaptations of notothenioid fishes: comparisons between cold temperate South American and New Zealand species and Antarctic species.

Fishes of the perciform suborder Notothenioidei afford an excellent opportunity for studying the evolution and functional importance of diverse types of biochemical adaptation to temperature. Antarctic notothenioids have evolved numerous biochemical adaptations to stably cold waters, including antifreeze glycoproteins, which inhibit growth of ice crystals, and enzymatic proteins with cold-adapted specific activities (k(cat) values) and substrate binding abilities (K(m) values), which support metabolism at low temperatures. Antarctic notothenioids also exhibit the loss of certain biochemical traits that are ubiquitous in other fishes, including the heat-shock response (HSR) and, in members of the family Channichthyidae, hemoglobins and myoglobins. Tolerance of warm temperatures is also truncated in stenothermal Antarctic notothenioids. In contrast to Antarctic notothenioids, notothenioid species found in South American and New Zealand waters have biochemistries more reflective of cold-temperate environments. Some of the contemporary non-Antarctic notothenioids likely derive from ancestral species that evolved in the Antarctic and later "escaped" to lower latitude waters when the Antarctic Polar Front temporarily shifted northward during the late Miocene. Studies of cold-temperate notothenioids may enable the timing of critical events in the evolution of Antarctic notothenioids to be determined, notably the chronology of acquisition and amplification of antifreeze glycoprotein genes and the loss of the HSR. Genomic studies may reveal how the gene regulatory networks involved in acclimation to temperature differ between stenotherms like the Antarctic notothenioids and more eurythermal species like cold-temperate notothenioids. Comparative studies of Antarctic and cold-temperate notothenioids thus have high promise for revealing the mechanisms by which temperature-adaptive biochemical traits are acquired - or through which traits that cease to be of advantage under conditions of stable, near-freezing temperatures are lost - during evolution.