Cellular dinitrosyl iron complexes (DNICs) have long been considered NO carriers. Although other physiological roles of DNICs have been postulated, their chemical functionality outside of NO transfer has not been demonstrated thus far. Here we report unprecedented dioxygen reactivity of an N-bound {Fe(NO)2}10 DNIC, [Fe(TMEDA)(NO)2] (1). In the presence of O2, 1 becomes a nitrating agent that converts 2,4,-di-tert-butylphenol to 2,4-di-tert-butyl-6-nitrophenol via formation of a putative iron-peroxynitrite [Fe(TMEDA)(NO)(ONOO)] (2) that is stable below −80 °C. Iron K-edge X-ray absorption spectroscopy on 2 supports a five-coordinated metal center with a bound peroxynitrite in a cyclic bidentate fashion. The peroxynitrite ligand of 2 readily decays at increased temperature or under illumination. These results suggest that DNICs could have multiple physiological or deleterious roles, including that of cellular nitrating agents.

Generation of hydroxyl radicals in the presence of buffered terephthalate solution produces flourescent 2‐hydroxyterephthalate. Wool, nylon, cotton and polyester all generate hydroxyl radicals when irradiated with UVA light, and to a lesser extent with blue light, in terephthalate solution. Trace metal ions (particularly iron and copper) contribute to hydroxyl radical generation in wool and cotton. UVA irradation of wool in deuterated solution does not affect the concentration of hydroxyl radicals or the amount of yellowing observed relative to undeuterated solution. This suggests that 1O2 is not involved in the wet photoyellowing of wool. Although the photoinitiation stages are clearly different, it is likely that similar free radical processes are responsible for both hydroxyl radical production and wet photoyellowing in all four fibre types. This straight forward fluorescence technique has potential to correlate the free radical photodegeneration of fibres in the presence of various additives designed to improve performance.

Glucitol-core containing gallotannins (GCGs) are polyphenols containing galloyl groups attached to a 1,5-anhydro-D-glucitol core, which is uncommon among naturally occurring plant gallotannins. GCGs have only been isolated from maple (Acer) species, including the red maple (Acer rubrum), a medicinal plant which along with the sugar maple (Acer saccharum), are the major sources of the natural sweetener, maple syrup. GCGs are reported to show antioxidant, α-glucosidase inhibitory, and antidiabetic effects, but their antiglycating potential is unknown. Herein, the inhibitory effects of five GCGs (containing 1–4 galloyls) on the formation of advanced glycation end-products (AGEs) were evaluated by MALD-TOF mass spectroscopy, and the BSA-fructose, and G.K. peptide-ribose assays. The GCGs showed superior activities compared to the synthetic antiglycating agent, aminoguanidine (IC50 15.8–151.3 vs. > 300 μM) at the early, middle, and late stages of glycation. Circular dichroism data revealed that the GCGs were able to protect the secondary structure of BSA protein from glycation. The GCGs did not inhibit AGEs formation by the trapping of reactive carbonyl species, namely, methylglyoxal, but showed free radical scavenging activities in the DPPH assay. The free radical quenching properties of the GCGs was further confirmed by electron paramagnetic resonance spectroscopy using ginnalin A (contains 2 galloyls) as a representative GCG. In addition, this GCG chelated ferrous iron, an oxidative catalyst of AGEs formation, supporting a potential antioxidant mechanism of antiglycating activity for these polyphenols. Therefore, GCGs should be further investigated for their antidiabetic potential given their antioxidant, α-glucosidase inhibitory, and antiglycating properties.

The riboflavin-sensitized photooxidation of ascorbate ion (HA-) to ascorbate radical (A.-) was followed by electron spin resonance (ESR) spectroscopy in conjunction with oxygen depletion measurements. In air-saturated aqueous media, steady-state amounts of A.- are rapidly established upon irradiation. The ESR signal disappears within a few seconds after the light is extinguished--more slowly under constant irradiation as oxygen is depleted. No photooxidation was observed in deaerated media. Similar results were obtained with other flavins and when ascorbyl palmitate was substituted for HA-. The effect of added superoxide dismutase, catalase, desferrioxamine, and singlet oxygen scavengers (NaN3 and tryptophan) was studied, as was replacement of water by D2O and saturation with O2. The results are indicative of ascorbate free radical production via direct reaction between ascorbate ion and triplet riboflavin in the presence of O2. While the presence of superoxide ion tends to reduce the steady-state concentration of A.-, competition from the reaction of HA- with singlet oxygen is less apparent in this system (at HA- > or = 1 mM) than in the previously studied aluminum phthalocyanine tetrasulfonate-photosensitized reaction.