7722-17-0Relevant academic research and scientific papers
Multi-faceted reactivity of alkyltellurophenols towards peroxyl radicals: Catalytic antioxidant versus thiol-depletion effect
Amorati, Riccardo,Valgimigli, Luca,Diner, Peter,Bakhtiari, Khadijeh,Saeedi, Mina,Engman, Lars
, p. 7510 - 7522 (2013)
Hydroxyaryl alkyl tellurides are effective antioxidants both in organic solution and aqueous biphasic systems. They react by an unconventional mechanism with ROO. radicals with rate constants as high as 107 M-1 s-1 at 303 K, outperforming common phenols. The reactions proceed by oxygen atom transfer to tellurium followed by hydrogen atom transfer to the resulting RO. radical from the phenolic OH. The reaction rates do not reflect the electronic properties of the ring substituents and, because the reactions occur in a solvent cage, quenching is more efficient when the OH and TeR groups have an ortho arrangement. In the presence of thiols, hydroxyaryl alkyl tellurides act as catalytic antioxidants towards both hydroperoxides (mimicking the glutathione peroxidases) and peroxyl radicals. The high efficiency of the quenching of the peroxyl radicals and hydroperoxides could be advantageous under normal cellular conditions, but pro-oxidative (thiol depletion) when thiol concentrations are low. Anti- and pro-oxidants: Hydroxyaryl alkyl tellurides are unconventional antioxidants able to quench chain-carrying peroxyl radicals with rate constants as high as 107 M-1 s-1 by a mechanism involving oxygen atom transfer to tellurium followed by reaction of the RO. radical with the phenol (see figure). They can also catalytically decompose both the ROO. radical and H2O2 in the presence of excess thiols. Copyright
UVA irradiation of fatty acids and their oxidized products substantially increases their ability to generate singlet oxygen
Regensburger, Johannes,Maisch, Tim,Knak, Alena,Gollmer, Anita,Felgentraeger, Ariane,Lehner, Karin,Baeumler, Wolfgang
, p. 17672 - 17680 (2013/11/06)
UVA radiation plays an important role for adverse reactions in human tissue. UVA penetrates epidermis and dermis of skin being absorbed by various biomolecules, especially endogenous photosensitizers. This may generate deleterious singlet oxygen (1O2) that oxidizes fatty acids in cell membranes, lipoproteins, and other lipid-containing structures such as the epidermal barrier. Indications exist that fatty acids are not only the target of 1O2 but also act as potential photosensitizers under UVA irradiation, if already oxidized. Five different fatty acids in ethanol solution (stearic, oleic, linoleic, linolenic and arachidonic acid) were exposed to UVA radiation (355 nm, 100 mW) for 30 seconds. 1O 2 luminescence was detected time-resolved at 1270 nm and confirmed in spectrally-resolved experiments. The more double bonds fatty acids have the more 1O2 photons were detected. In addition, fatty acids were continuously exposed to broadband UVA for up to 240 min. During that time span, UVA absorption and 1O2 luminescence substantially increased with irradiation time, reached a maximum and decreased again. HPLC-MS analysis showed that the amount of peroxidized fatty acids and the 1O2 generation increased and decreased in parallel. This indicates the high potential of peroxidized fatty acids to produce 1O2 under UVA irradiation. In conclusion, fatty acids along with peroxidized products are weak endogenous photosensitizers but become strong photosensitizers under continuous UVA irradiation. Since fatty acids and their oxidized products are ubiquitous in living cells and in skin, which is frequently and long-lasting exposed to UVA radiation, this photosensitizing effect may contribute to initiation of deleterious photooxidative processes in tissue.
