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Free Radicals and Antioxidants
Published in Chuong Pham-Huy, Bruno Pham Huy, Food and Lifestyle in Health and Disease, 2022
Chuong Pham-Huy, Bruno Pham Huy
Structurally, the difference between lutein and zeaxanthin is in the type of ionone ring; lutein contains a β-ionone ring and a ε-ionone ring, whereas zeaxanthin has two β-ionone rings. Lutein and zeaxanthin are isomers, but not stereoisomers, which differ in the location of a double bond unsaturation in the end ring (134). Lutein can exist in eight possible stereoisomeric forms because of three chiral centers, but in nature it exists mainly in Z (cis)-form (R,R,R). Zeaxanthin, on the other hand, has two chiral centers but, because of symmetry, exists only in three stereoisomeric forms: (R,R), (S,S), and (R,S-meso) (134). The strong antioxidant activity of lutein and zeaxanthin is due to numerous conjugated double bonds in their lateral chain. Lutein and zeaxanthin are fat-soluble molecules and are generally insoluble in water.
Chemistry of Essential Oils
Published in K. Hüsnü Can Başer, Gerhard Buchbauer, Handbook of Essential Oils, 2020
α-Bisabolol (115) is the simplest of the cyclic sesquiterpenoid alcohols. If farnesol is the sesquiterpenoid equivalent of geraniol and nerolidol of linalool, then α-bisabolol is the equivalent of α-terpineol. It has two chiral centers and therefore exists in four stereoisomeric forms, all of which occur in nature. The richest natural source is Myoporum crassifolium Forst., a shrub from New Caledonia, but α-bisabolol can be found in many other species including chamomile, lavender, and rosemary. It has a faint floral odor and anti-inflammatory properties and is responsible, at least in part, for the related medicinal properties of chamomile oil.
The Role of Tocopherols in Health
Published in Robert E.C. Wildman, Richard S. Bruno, Handbook of Nutraceuticals and Functional Foods, 2019
The majority of vitamin E supplements contain α-tocopherol, although γ-tocopherol supplements are increasingly common. The latter, however, generally contain a mixed tocopherol/tocotrienol formulary with γ-tocopherol as the predominant form. Regarding α-tocopherol, most supplements and fortified foods contain synthetic α-tocopherol (all rac-α-tocopherol, commonly labeled as dl-α-tocopherol) rather than naturally occurring α-tocopherol (RRR-α-tocopherol, labeled as d-α-tocopherol). Although natural and synthetic compounds are similar in their bioactivity for many dietary supplements, this is not the case with α-tocopherol. α-tocopherol has three chiral centers (carbon positions 2, 4′, and 8′; Figure 6.1), which yields eight stereoisomers (2R forms: RRR, RSR, RRS, RSS; 2S forms: SRR, SSR, SRS, SSS). Synthetic α-tocopherol supplements actually contain eight equimolar amounts of each stereoisomer, whereas naturally occurring α-tocopherol is exclusively RRR-α-tocopherol.58
A patent review of adenosine A2B receptor antagonists (2016-present)
Published in Expert Opinion on Therapeutic Patents, 2022
Beatrice Francucci, Diego Dal Ben, Catia Lambertucci, Andrea Spinaci, Rosaria Volpini, Gabriella Marucci, Michela Buccioni
Forty-three pyridone derivatives able to modulate the A2A/A2BARs were patented in 2020 [115]. The compounds of this invention were tested in CHO cells stable transfected with adenosine receptors and their KB on A2A and A2BARs were obtained through the quantification of intracellular cAMP. All of them have a high affinity toward A2AAR, while as regards A2BR this parameter varies according to the substituents present in the central nucleus. Chirality of the carbon is also important for the activity. The stereoisomer 1-[(R)-1-(2-hydroxy-2-methylpropionyl)-3-pyrrolidinyl]-3-{[4-(2-amino-8-methoxy-4-quinazolinyl)-1 H-1,2,3-triazol-1-yl]methyl}-1 H-pyridin-2-one is more affine than to its enantiomer especially vs A2BAR.
In vitro metabolism assessment of thiacloprid in rainbow trout and rat by LC-UV and high resolution-mass spectrometry
Published in Xenobiotica, 2021
Jose Serrano, Richard C. Kolanczyk, Brett R. Blackwell, Barbara R. Sheedy, Mark A. Tapper
The accurate mass for THI and metabolites TM1, TM2 and TM3, as determined from LC-HR-MS experiments (M + H), was 253.10226, 228.03574, 126.05475 and 128.02740 Da respectively, with all detected structures within a mass error <7 ppm (see Supplemental Tables S5 and S6). Specifically, LC-MS mass chromatograms of THI slice exposures showed the presence of two isomers for both TM1 and TM2 corresponding to the Z-/E-diastereoisomers of TMI (retention times of 1.189 and 1.437 min, respectively), and the enol-/aldehyde-tautomers of TM2 (0.917 and 1.233 min, respectively; Supplemental Table S6). Diastereoisomers are stereoisomers of the same constitution, but the molecules do not have a mirror-image relationship and have different physical and chemical properties. On the other hand, tautomers are molecules with the same molecular formula but different connectivity that are formed in common acid- or base-catalyzed processes.
Comparative toxicity and toxicokinetic studies of oxiracetam and (S)-oxiracetam in dogs
Published in Xenobiotica, 2019
Tian-tian Liu, Xin-miao Guo, Zu-yuan Rong, Xiang-feng Ye, Jin-feng Wei, Ai-ping Wang, Hong-tao Jin
As a consequence of the rapid advances in chiral synthesis and separation technologies, combined with new regulatory policies for chiral pharmaceuticals, chiral drugs have become an important focus for research and development of new molecular entities (Calcaterra & D'Acquarica, 2018; Nunez et al., 2009; Srinivas, 2004). Stereoisomers (enantiomers and diastereoisomers) not only differ from one another in their pharmacological effects, but also in their pharmacokinetic (adsorption, distribution, biotransformation, and excretion) profiles (Brocks, 2006; Hutt, 2007) and toxicological properties (Natarajan & Basak, 2011; Smith, 2009). Understanding the stereospecificity of in vitro and in vivo pharmacokinetics/toxicokinetics may assist in delineating the developmental path of the racemate and/or the pure enantiomers. The differential actions and toxicities determine enantiomer selection to maximize clinical effects or mitigate drug toxicity. Toxicological evaluation of chiral drugs, therefore, deserves increased attention.