China
Africa
Explore chapters and articles related to this topic
Ergogenic Aids
Published in Michael H. Stone, Timothy J. Suchomel, W. Guy Hornsby, John P. Wagle, Aaron J. Cunanan, Strength and Conditioning in Sports, 2023
Michael H. Stone, Timothy J. Suchomel, W. Guy Hornsby, John P. Wagle, Aaron J. Cunanan
Vitamin C (or ascorbic acid) is essential for many physiologic functions and must be obtained exogenously since it cannot be synthesized by humans (3). It plays an important role in the athlete’s defense mechanisms against ROS, which are elevated during training and performance (50). More specifically, vitamin C has demonstrated the ability to reduce delayed onset muscle soreness and creatine kinase concentrations following eccentric exercise (29). It possesses strong reducing properties and contributes to redox cycling through generating transition metal ions (e.g., Fe3+ to Fe2+; Cu2+ to Cu+) that stimulate free radical chemistry (83). In addition to the direct free radical scavenging activity, vitamin C supports collagen synthesis as a positive regulator and is therefore beneficial for athletes with respect to tendon, ligament, bone, and blood vessel health and function (36, 100). Lastly, vitamin C plays an important role in enhancing the antioxidant action of vitamin E (3, 83). Because the phenol group of tocopherol is located at the water-membrane interface of biological membranes, interaction between vitamin C and vitamin E occurs and facilitates antioxidant action (83). Therefore, vitamin C plays a fundamental role in the antioxidant network. However, if taken in excess, there is also evidence that vitamin C may induce damage and it is therefore not recommended to dose in excess of the upper limit of the recommended daily allowance (3).
Chronic pancreatitis
Published in David Westaby, Martin Lombard, Therapeutic Gastrointestinal Endoscopy A problem-oriented approach, 2019
In addition to analgesia, the avoidance of alcohol is thought to be important, but there are no data on which to judge whether this helps to relieve pain. Other strategies have been to reduce pancreatic secretion with somatostatin analogues and to replenish antioxidant levels on the grounds that some of the damage is mediated by free radical chemistry.
New Biological Targets for the Treatment of Leishmaniasis
Published in Venkatesan Jayaprakash, Daniele Castagnolo, Yusuf Özkay, Medicinal Chemistry of Neglected and Tropical Diseases, 2019
Fabrizio Carta, Andrea Angeli, Christian D.-T. Nielsen, Claudiu T. Supuran, Agostino Cilibrizzi
Both methodologies rely upon the activation of the carboxylic acid moiety to a redox active ester which could be isolated or reacted in situ. Even though the mechanism proceeds via a radical pathway (confirmed by Aggarwal’s studies employing radical clock experiments), the methodology could functionalize a variety of complex natural products, demonstrating exquisite control not often associated with traditional radical chemistry (Figures 18A and B). Of note, a borono-vancomycin analogue was obtained as a single diastereomer from vancomycin (Li et al. 2017). Aggarwal (A) and Baran’s (B) decarboxylative borylations. THF = tetrahydrofuran; DMF = dimethylformamide; B2Pin2 = bis(pinacolato)diboron; DMAc = N,N-dimethylacetamide.
Response to “Hydroxyl radical is predominantly involved in oxidatively generated base damage to cellular DNA exposed to ionizing radiation” by Cadet et al.
Published in International Journal of Radiation Biology, 2023
Cynthia Burrows, Aaron Fleming
We recently reviewed the aspects of guanine oxidation chemistry in which we compared and contrasted oxidation by ionizing radiation vs. endogenous oxidative stress (Fleming and Burrows 2022). Cadet et al. (2022) and Halliwell et al. (2021) repeatedly mis-state our work as involving “conversion of highly reactive •OH into mildly oxidizing carbonate anion radical.” The reaction of •OH with bicarbonate is slow, and it has never been proposed to be relevant in our work with endogenous oxidative stress. Rather, the Fenton reaction of Fe(II) complexes, with or without bound phosphate, with hydrogen peroxide in the presence of bicarbonate proceeds by an inner-sphere mechanism (Cotton and Wilkinson 1972), consistent with the results of Meyerstein et al. (Illes et al. 2019). In such a reaction, hydroperoxide and carbonate are both bound to Fe(II) and react at pH 7 to produce carbonate radical anion directly, without any intermediate formation of •OH. In accord with this mechanism, we demonstrated that the presence of bicarbonate in the Fenton reaction leads to a different set of guanine oxidation products than that seen from classical radiation (hydroxyl radical) chemistry (Fleming and Burrows 2020).
Synthesis and structure-activity relationships of novel 5-(hydroxamic acid)methyl oxazolidinone derivatives as 5-lipoxygenase inhibitors
Published in Journal of Enzyme Inhibition and Medicinal Chemistry, 2020
Oludotun A. Phillips, Mira A. Bosso, Charles I. Ezeamuzie
Generally, 5-LO inhibitors can be classified into 4 main types based on their mechanism of action: (i) substrate or competitive analogues, (ii) inhibitors of 5-LO activating protein (FLAP), (iii) redox-active inhibitors that could interfere with the free radical chemistry, (iv) iron-chelating (Fe3+ ion) inhibitors – bind the putative iron at the active site11. Several compounds based on these four different types have been synthesised, isolated as natural products and investigated as potent selective inhibitors of 5-LO with promising therapeutic usefulness3,7. However, only few 5-LO inhibitors progress to clinical trials due to insufficient bioavailability, pharmacokinetics and/or toxicity related problems12.
First line defence antioxidants-superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPX): Their fundamental role in the entire antioxidant defence grid
Published in Alexandria Journal of Medicine, 2018
There are many and various types of free radicals in biological systems, however, those derived from oxygen, generally termed reactive oxygen species (ROS) are of major concern and interest to researchers in the field of free radical chemistry. Oxygen is highly susceptible to free radical formation because of its electronic structure. The molecule has in its outer shell, two unpaired electrons in separate electronic orbitals. Oxygen radicals such as superoxide anion (∗O2) and singlet oxygen, (1O2−) are easily generated from the sequential reduction of molecular oxygen via step-wise addition of electrons.