A new generation of cysteine derivatives with three active antioxidant centers: improving reactivity and stability

Catalytic Antioxidant Activity of Two Diterpenoid Polyphenols of Rosemary, Carnosol, and Isorosmanol, against Lipid Oxidation in the Presence of Cysteine Thiol

Lamiaceae herbs such as rosemary have excellent antioxidant properties, and lipidic diterpenoid constituents, such as carnosol, are known as characteristic components to exhibit strong antioxidant activity. This study investigates the effect of thiol compounds on the antioxidant properties of diterpenoid polyphenols. The results concerning the antioxidant activity of polyphenols in the presence of thiol showed that two polyphenols, namely, carnosol and isorosmanol, enhanced antioxidant capacity against the radical-induced oxidation of lipids. Further examination of the mechanism revealed that both polyphenols exhibit excellent catalytic antioxidant activity by using the thiol group as a reduction source. Using density functional theory calculations, we attempted to explain why only these two polyphenols exhibit catalytic antioxidant properties. The calculation results and the assumed reaction mechanism suggested that the orthoquinones produced in the antioxidant reactions of carnosol and isorosmanol are more unstable than the others and that the regioselectivity of their reactions with thiols contributes to their catalytic antioxidant properties.

Photoelectron Spectroscopic Study of Ascorbate and Deprotonated Ascorbate Anions Using an Electrospray Ion Source and a Cryogenically Cooled Ion Trap

Reactive oxygen species (ROS) in biological systems are formed through a variety of mechanisms. These species are very reactive and have been associated with many diseases, including cancer and cardiovascular disease. One way of removing ROS from the body is through the use of radical scavengers, which are compounds capable of giving up an electron to neutralize the ROS yet form a stable radical species themselves. A common radical scavenger is ascorbic acid, also known as vitamin C. At physiological pH, ascorbic acid is predominately present as the ascorbate anion, C₆H₇O₆^-. The ascorbate anion, as well as the dianion (C₆H₆O₆^2-), is an effective antioxidant due to its ability to donate an electron from a lone pair generated by deprotonation. An electrospray ionization source was added to our pulsed anion photoelectron spectrometer to study ascorbate anions and deprotonated ascorbate dianions via photoelectron spectroscopy. The antioxidant behavior of the ascorbate anion and the deprotonated ascorbate dianion was confirmed based on the experimental vertical detachment energy (VDE), and, therefore, the ionization energy of the anions, 3.85 and 2.68 eV, respectively.

Supercritical Antisolvent Fractionation of Antioxidant Compounds from Salvia officinalis

The increasing interest towards greener antioxidants obtained via natural sources and more sustainable processes encourages the development of new theoretical and experimental methods in the field of those compounds. Two advanced separation methods using supercritical CO2 are applied to obtain valuable antioxidants from Salvia officinalis, and a first approximation to a QSAR model relating molecular structure with antioxidant activity is explored in order to be used, in the future, as a guide for the preselection of compounds of interest in these processes. Separation experiments through antisolvent fractionation with supercritical CO2 were designed using a Response Surface Methodology to study the effect of pressure and CO2 flow rate on both mass yields and capability to obtain fractions enriched in three antioxidant compounds: chlorogenic acid, caffeic acid and rosmarinic acid which were tracked using HPLC PDA. Rosmarinic acid was completely retained in the precipitation vessel while chlorogenic and caffeic acids, though distributed between the two separated fractions, had a major presence in the precipitation vessel too. The conditions predicted for an optimal overall yield and enrichment were 148 bar and 10 g/min. Although a training dataset including much more compounds than those now considered can be recommended, descriptors calculated from the σ-profiles provided by COSMO-RS model seem to be adequate for estimating the antioxidant activity of pure compounds through QSAR.

Stability of biodiesel, its improvement and the effect of antioxidant treated blends on engine performance and emission

Biodiesel consists of long chain fatty acid esters derived from vegetable oils, animal fats, and used oils.