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Heterocyclic Drugs from Plants
Published in Rohit Dutt, Anil K. Sharma, Raj K. Keservani, Vandana Garg, Promising Drug Molecules of Natural Origin, 2020
Debasish Bandyopadhyay, Valeria Garcia, Felipe Gonzalez
Aromaticity is dependent upon the structure of a molecule and determines physical and chemical properties. As stated earlier, pyrroles possess a heteroaromatic ring having six π (pi) electrons and a heteroatom (N). Pyrrole is weakly basic because the nitrogen has a lone pair of electrons (also patriciate to fulfill Hückel’s rule) that can accept protons. Thus, pyrroles are both aBrønsted and Lewis base. All the ring constituents are sp2 hybridized having a delocalized π (pi) bonding system in. The sidewise overlap of un-hybridized orbital’s results the delocalized π (pi)-electron cloud, which accounts for the aromatic character of pyrrole. For a molecule to be aromatic, it must be cyclic and planar, having delocalized π (pi)-electrons, and fulfilHuckel’s rule of (4n+2) π (pi)-electrons. Pyrrole obeys all these criteria as a heteroaromatic compound.
Reactivities of Amino Acids and Proteins with Iodine
Published in Erwin Regoeczi, Iodine-Labeled Plasma Proteins, 2019
The heterocyclic imidazole ring is composed of three carbon and two nitrogen atoms as shown in Figure 45 (Structure A). In accordance with its aromaticity, the ring is planar and shows resonance (i.e., electron delocalization). The resonance energy (i.e., the difference in energy between the actual molecule and that calculated for the best hypothetical resonance structure) for imidazole at 15.43 kcal/mol is high, implying the stability of the structure (the corresponding value, obtained by the same method; is 20.04 for benzene, 20.94 for pyridine, and 8.53 for the less stable pyrrole).82
Spectroscopy and Fluorimetry
Published in Joseph Chamberlain, The Analysis of Drugs in Biological Fluids, 2018
The first consideration is that the compound must have strong absorption characteristics to provide the energy for eventual emission. The next consideration is the quantum yield of fluorescence. For consideration of structures with high quantum yields the various review papers should be consulted. A few general rules on structures that may be expected to yield high fluorescence may be drawn up, but it would be wise to investigate any new drug for unexpected phenomena. Aromaticity appears to be a prerequisite for fluorescence, with most simple aromatic compounds having quantum yields of approximately 0.20. This fluorescence is modified by ring substitution (Table 4.7). The efficiency of fluorescence, however, by no means follows the degree of absorbance, as evidenced by the low fluorescence of nitrobenzene, the nitro group apparently enhancing the degree of internal conversion. The pH of the solution has a dramatic influence on fluorescence, as fluorescent compounds are often used as pH indicators.
Novel amides of mycophenolic acid and some heterocyclic derivatives as immunosuppressive agents
Published in Journal of Enzyme Inhibition and Medicinal Chemistry, 2022
Juliusz Maksymilian Walczak, Dorota Iwaszkiewicz-Grześ, Michalina Ziomkowska, Magdalena Śliwka-Kaszyńska, Mateusz Daśko, Piotr Trzonkowski, Grzegorz Cholewiński
Heterocyclic motifs are one of the most important constitutional patterns among all existing pharmaceuticals’ structures. In 2014, four of five most common prescribed drugs in the US contained heterocyclic fragments24. Of 59% of small-molecule remedies sold in the US, in the same year, also carried heterocyclic designs, but this time it belonged to the nitrogen-based heterocyclic compounds family25. These facts render heterocycles as being the most privileged and significant molecular architectures in the drug designing area. Heterocyclic structural units are known for their remarkable physicochemical properties. They may serve as versatile bioisosteres as they can be tuned in their lipophilicity, polarity and water-solubility upon currently desirable properties in molecular targets reaching. These features may be manipulated in relation to their aromaticity and polar properties developed by the presence of strong electronegative atoms24. Referring to previously mentioned examples, heterocyclic structural motifs such as 1,2,4-triazole, incorporated into MPA molecule, have shown similar activity towards IMPDH as MPA within itself15. Inhibitory properties of benzoxazole-based derivatives towards parasitical IMPDH have also been proved, making them potential antiparasitic agents26. Heterocyclic compounds are also known for their anti-inflammatory27, anticancer28,29, antimalarial30, and fungicidal properties31 and these parameters may be a source of added value beside antiproliferative nature of MPA.
Searching for drug leads targeted to the hydrophobic cleft of dengue virus capsid protein
Published in Journal of Enzyme Inhibition and Medicinal Chemistry, 2022
Liliane O. Ortlieb, Ícaro P. Caruso, Nathane C. Mebus-Antunes, Andrea T. Da Poian, Elaine da C. Petronilho, José Daniel Figueroa-Villar, Claudia J. Nascimento, Fabio C. L. Almeida
To investigate the intermolecular interaction between DENVC and the selected compounds, we also analysed relaxation parameters57. We measured proton relaxation times T1 and T2 for the selected compounds in the presence and absence of DENVC (Table 1). Changes in T1 and T2 values for compounds 1, 4, 12, 15, and 16 after the addition of the protein corroborate the STD experiments, showing that all compounds interact with DENVC. As expected for binding, T2 of all compounds increased in the presence of the protein, with the exception of hydrogen 1 of compounds 1 and 16. This change could be a result of the presence of conformational exchange at this site in the free ligand that is reduced upon binding. Interestingly, it occurred in the same site for both compounds. The aromatic hydrogens of all compounds presented major T2 changes, suggesting the aromaticity of these compounds is important for the interaction.
The toxicology of air pollution predicts its epidemiology
Published in Inhalation Toxicology, 2018
Andrew J. Ghio, Joleen M. Soukup, Michael C. Madden
HULIS is a mixture of complex, organic, macromolecular compounds initially extracted from atmospheric aerosol particles and isolated from fog and cloud water (Dinar et al., 2006; Graber & Rudich, 2006; Jacobson et al., 2000; Zheng et al., 2013). They derive their name from their similarities to terrestrial and aquatic humic and fulvic acids in characteristics of ultraviolet-visible, Fourier-transform infrared and nuclear magnetic resonance spectroscopies. HULIS share components with HS including carboxylate and aromatic groups but differ in having a smaller average molecular weight and lower aromaticity (Graber & Rudich 2006). HULIS contain both soluble and insoluble fractions. These substances are recognized to be a component of many combustion products. HULIS have also been isolated from PM in cigarette smoke and combustion products including wood smoke particle, diesel exhaust particle, and emissions from the burning of biomass (Forrister et al., 2015; Ghio et al., 1994, 1996; Hoffer et al., 2006; Stedman et al., 1966). There is the potential secondary formation of HULIS following atmospheric oxidation of soot particles, levoglucosan, α-pinene and isoprene (Decesari et al., 2002; Holmes & Petrucci, 2007; Iinuma et al., 2004; Limbeck et al., 2003). Evidence supporting such secondary formation of HULIS has been provided in field studies (Krivacsy et al., 2008). HULIS from combustion products can be lower in oxygen content, relative to HS in the natural organic matter, consistent with a loss of oxygen-containing functional groups such as that which follows a heating of HS (Perdue, 1985).