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Transformation of Natural Products by Marine-Derived Microorganisms
Published in Se-Kwon Kim, Marine Biochemistry, 2023
Thayane Melo de Queiroz, André Luiz Meleiro Porto
De Lise and co-workers (2016) described the isolation, recombinant expression in E. coli, and partial characterisation of a α-L-rhamnosidase (α-RHA) obtained from the marine bacteria Novosphingobium sp. PP1Y, which was isolated from surface seawater (Italy). In this study, the α-RHA enzyme was used in the hydrolysis of the flavonoids naringin, rutin, and neohesperidin dihydrochalcone into their glycosylated derivatives. The reactions were performed in Na-phosphate buffer (pH 7.0) under magnetic stirring at 40°C for 1–3 hours (Figure 5.9).
Peripheral Mechanisms of Mammalian Sweet Taste
Published in Robert H. Cagan, Neural Mechanisms in Taste, 2020
William Jakinovich, Dorothy Sugarman
Two compounds shown to taste sweet to humans, naringen dihydrochalchone and neohesperidin dihydrochalcone (NHDHC), were tested electrophysiologically in the gerbil.26 Electrophysiological taste responses were noted at a 1 mM concentration. However, in subsequent behavioral (CTA) experiments, the gerbils rejected these compounds at 1 mM, but did drink them in 0.2 mM diluted solutions. When this lower concentration was later tested in a CTA experiment, it failed to evoke an avoidance in the gerbils trained to avoid sucrose, NaCl, HC1, or quinine. The results suggest that these two sweetener compounds possess some unknown taste quality not represented by the prototypical group. It was also observed in two-bottle preference studies (NHDHC vs. water)153 that rats will drink less NHDHC than water if the concentrations are higher than 8 mM. Actually, in rat whole nerve electrophysiological experiments,153 NHDHC produced slightly larger responses in the glossopharyngeal nerve than in the chorda tympani nerve. On the other hand, baboons preferred NHDHC to water at concentrations less than 0.16 mM.153
Activation of Nrf2 signaling pathway by natural and synthetic chalcones: a therapeutic road map for oxidative stress
Published in Expert Review of Clinical Pharmacology, 2021
Melford Chuka Egbujor, Sarmistha Saha, Brigitta Buttari, Elisabetta Profumo, Luciano Saso
Han et al [128] reported a new neohesperidin dihydrochalcone derivative (48) that exhibited significant inhibitory effect against adipogenic differentiation of human adipose-derived stem cells via Nrf2 activation. They observed that compound 48 effectively activated Nrf2 thereby inducing the expression of the antioxidant enzymes mediated by HO-1 and NQO-1 expressions and consequently reduced ROS generation in adipogenic differentiation. They suggested that compound 48 could be a potential drug for the treatment of obesity. Wu et al [3] synthesized a chalcone derivative (49) that inhibited H2O2–induced apoptosis in PC12 cells. Compound 49 significantly activates Nrf2 pathway and therefore could be used as a candidate drug for the treatment of oxidative stress mediated diseases [3]. Compound 49 had a preconditioning effect on Nrf2-ARE activation, thereby preventing oxidative stress-induced neuronal cell death [3].
Insights into the intestinal bacterial metabolism of flavonoids and the bioactivities of their microbe-derived ring cleavage metabolites
Published in Drug Metabolism Reviews, 2018
Xinchi Feng, Yang Li, Mahmood Brobbey Oppong, Feng Qiu
Based on the intestinal bacterial metabolic pathway of luteolin, flavanones can be produced after the first reduction reaction. This suggests that the natural flavanones can follow the same degradation pathways as luteolin. Many flavanones including naringenin, hesperetin, eriodictyol, and homoeriodictyol investigated have indicated that they follow similar metabolism pathways (Booth et al. 1958; Rechner et al. 2002; Labib et al. 2004; Rechner et al. 2004; Zou et al. 2014; Orrego-Lagaron et al. 2015). Chalcone acts as an intermediate in metabolic processes of luteolin. Does this mean that chalcones would undergo similar metabolism and produce hydroxyphenylpropionic acid derivatives? This hypothesis was tested by Braune et al. (2005). Neohesperidin dihydrochalcone can be converted to 3-(3-hydroxy-4-methoxyphenyl)propionic acid or 3-(3,4-dihydroxyphenyl)propionic acid by human fecal slurries. However, in the metabolic profiles study of xanthohumol, a prenylated chalcone, no hydroxyphenylpropionic acid derivatives were reported as metabolites (Yilmazer et al. 2001; Herath et al. 2003; Nookandeh et al. 2004; Nikolic et al. 2005; Hanske et al. 2010). After xanthohumol had been fed to rats in a dose of 1000 mg/kg, 22 metabolites were isolated in rat feces (Nookandeh et al. 2004). Twenty metabolites had a modified chalcone structure and two metabolites were flavanone derivatives (Nookandeh et al. 2004). More investigations are still needed to confirm whether chalcone, such as xanthohumol, can undergo C-ring fission.
Intra-site differential inhibition of multi-specific enzymes
Published in Journal of Enzyme Inhibition and Medicinal Chemistry, 2020
Mario Cappiello, Francesco Balestri, Roberta Moschini, Umberto Mura, Antonella Del-Corso
The experimental measurements of the inhibition kinetic parameters that were independently conducted on the two substrates (as usually occurs in inhibitor screening) refer to “apparent” inhibitory constants (i.e. appKi, appK′i), whose relative values may lead to apparent incongruities. For example, if the experimental data indicate a mixed type of inhibition for substrate B and an uncompetitive inhibition for substrate A, as in neohesperidin dihydrochalcone (NHDC), which has been assessed as an inhibitor of the reduction of L-idose (substrate B) and HNE (substrate A) catalysed by AKR1B120. The results of the analysis of substrate B shows that the inhibitor may target the free enzyme, and thus this should also result from the analysis of substrate A. However, the data suggest that the inhibitor targets only the EA complex. This apparently contradictory situation can be rationalised although not completely, in the following ways: (i) the measured apparent inhibitory constants can be regarded as true dissociation constants, in which the K′i for substrate A is significantly lower than the Ki measured for substrate B (which is not the case for NHDC); and/or (ii) the measured constants are indeed “apparent” and the ternary complexes EIA, which is generated by adding A to the EI complex, and EAI, which is generated by adding I to the EA complex, are kinetically different and only EIA is able to evolve into products. Thus, once the potential DI has been identified through individual substrate analysis, it will be necessary to proceed analysing the simultaneous presence of the competing substrates for a conclusive evaluation of the differential inhibitory ability of the selected molecule.