305-01-1Relevant articles and documents
Photo-degradation of trans-caffeic acid in aqueous solution and influence of complexation by metal ions
Le Person, Anna?g,Lacoste, Anne-Sophie,Cornard, Jean-Paul
, p. 10 - 19 (2013)
The photo-degradation of metal complexes of caffeic acid was compared to the photo-degradation of free caffeic acid by using UV-vis spectroscopy and HPLC-ESI-mass spectrometry. This article reports first the determination of the products that are formed from the photo-degradation of trans-caffeic acid in aqueous solution and the investigation of the mechanism by a kinetic approach. The good fit between the model and the experimental concentration profiles confirms the photo-isomerization route of the molecule to cis-caffeic acid which then undergoes a cyclization to form the esculetin photo-product. In addition, it reveals, for the first time, another route of major importance leading to the product vinylcatechol. The presence of oxygen leads to an increase of the photo-isomerization rate. Then we report that metallic cations such as Al(III), Pb(II) and Cu(II) can influence the rate and mechanism of caffeic acid photodegradation. Al(III) ions slow down the photo-degradation whereas Pb(II) and Cu(II) ions have a promoter effect on the production of esculetin. In all cases, the photo-isomerization is reduced by the presence of metal ions and the formation of vinylcatechol does not occur.
COUMARINS OF Coronilla elegans
Kovalev, V. N..,Komissarenko, A. N.
, p. 228 (1984)
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Colorimetric and fluorescence signalling of thioesculetin in presence of oxidising agent
Shinde, Rupali G.,Khan, Ayesha A.,Barik, Atanu
, (2018)
Abstract: Thioesculetin (TE) is a sulfur analogue of esculetin. The UV-Vis absorption maximum of TE at 470 nm shifted to 357 nm in the presence of oxidising agent such as m-chloroperoxy benzoic acid (m-CPBA). With gradual increase in the m-CPBA concentrat
Study of umbelliferone hydroxylation to esculetin catalyzed by polyphenol oxidase
Garcia-Molina, Sea,Munoz-Munoz, Joseph Louis,Garcia-Molina, Francis,Rodriguez-Lopez, Joseph Neptune,Garcia-Canovas, Francis
, p. 1140 - 1145 (2013)
We characterize umbelliferone, a derivative of 2,4-dihydroxycoumaric acid, as a substrate of polyphenol oxidase. This enzyme hydroxylates umbelliferone to esculetin, its o-diphenol, and then oxidizes it to o-quinone. The findings show that umbelliferone, an intermediate in one of the coumarin biosynthesis pathways, may be transformed into its o-diphenol, esculetin, which is also an intermediate in the same pathway. The activity of the enzyme on umbelliferone was followed by measuring the consumption of oxygen, spectrophotometrically and by HPLC. Kinetic constants characterizing the hydroxylation process were: k cat=0.09±0.02 s-1 and Km=0.17±0. 06 mm. The o-diphenol, esculetin, was a better substrate and when its oxidation was followed spectrophotometrically, the kinetic constants were: k cat=1.31±0.25 s-1 and Km=0.035±0. 002 mM. Both compounds therefore can be considered as alternative substrates to l-tyrosine and l-3,4-dihydroxyphenylalanine (l-DOPA), since both indirectly inhibit melanogenesis.
Structure-Activity Relationship Study of Hydroxycoumarins and Mushroom Tyrosinase
Asthana, Shailendra,Zucca, Paolo,Vargiu, Attilio V.,Sanjust, Enrico,Ruggerone, Paolo,Rescigno, Antonio
, p. 7236 - 7244 (2015)
The structure-activity relationships of four hydroxycoumarins, two with the hydroxyl group on the aromatic ring of the molecule and two with the hydroxyl group replacing hydrogen of the pyrone ring, and their interactions with mushroom tyrosinase were studied. These compounds displayed different behaviors upon action of the enzyme. The two compounds, ar-hydroxylated 6-hydroxycoumarin and 7-hydroxycoumarin, were both weak substrates of the enzyme. Interestingly, in both cases, the product of the catalysis was the 6,7-hydroxycoumarin, although 5,6- and 7,8-isomers could also theoretically be formed. Additionally, both were able to reduce the formation of dopachrome when tyrosinase acted on its typical substrate, l-tyrosine. Although none of the compounds that contained a hydroxyl group on the pyrone ring were substrates of tyrosinase, the 3-hydroxycoumarin was a potent inhibitor of the enzyme, and the 4-hydroxycoumarin was not an inhibitor. These results were compared with those obtained by in silico molecular docking predictions to obtain potentially useful information for the synthesis of new coumarin-based inhibitors that resemble the structure of the 3-hydroxycoumarin.
Study of the Oxidative Cleavage Proposed in the Biogenesis of Transtaganolides/Basiliolides: Pyran-2-one Aromaticity-Mediated Regioselective Control and Biogenetic Implications
álvarez, José María,Jorge, Zacarías D.,Massanet, Guillermo M.
supporting information, (2020/03/05)
The synthetic feasibility of the oxidative cleavage: epoxidation of 7-O-geranylscopoletin followed by electrocyclic ring-opening, proposed in the biogenesis of transtaganolides/basiliolides is studied. Unlike the proposed pericyclic reactions, this pathway has not yet been addressed. Three synthetic strategies have been tested consisting of: i) Baeyer–Villiger oxidation of p-quinoids, ii) hydrolysis of quinone monoketals, or iii) direct fragmentation by using oxygen donors. Oxidation of the benzene ring of hydroxylated coumarins has been achieved using peroxyacids, but cleavage took place between undesired positions. The aromaticity conservation of the pyran-2-one cycle during oxidation is the controlling factor of these observed regioselectivities. The use of a 4,5-dihydroxy-2-methoxycinnamate model, in which the pyran-2-one ring does not exert influence on oxidation, has allowed the design of a synthetic sequence toward an analogue of the natural pyran-2-one isolated from Thapsia transtagana, key in the biogenesis. Mechanistic proposals for the obtained results as well as their biogenetic implications are raised.
Regioselective IBX-Mediated Synthesis of Coumarin Derivatives with Antioxidant and Anti-influenza Activities
Bizzarri, Bruno M.,Botta, Lorenzo,Capecchi, Eliana,Celestino, Ignacio,Checconi, Paola,Palamara, Anna T.,Nencioni, Lucia,Saladino, Raffaele
, p. 3247 - 3254 (2018/01/02)
Different catechol and pyrogallol derivatives have been synthesized by oxidation of coumarins with 2-iodoxybenzoic acid (IBX) in DMSO at 25 °C. A high regioselectivity was observed in accordance with the stability order of the incipient carbocation or radical benzylic-like intermediate. The oxidation was also effective in water under heterogeneous conditions by using IBX supported on polystyrene. The new derivatives showed improved antioxidant effects in the DPPH test and inhibitory activity against the influenza A/PR8/H1N1 virus. These data represent a new entry for highly oxidized coumarins showing an antiviral activity possibly based on the control of the intracellular redox value.
