Dissociation and keto-enol tautomerism of phloroglucinol and its anions in aqueous solution

Lohrie, Martin; Knoche, Wilhelm

doi:10.1021/ja00056a016

Cited by 29 publications

(24 citation statements)

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“…Since the exchange reactivity is mainly determined by the first step, the carbon atom which is more negatively charged would be more susceptible for attack by the deuterium atom. 30,35 In addition, it was found that the negatively charged oxygen-substitute group on aromatic ring is expected to stabilize the σ-complex intermediate, 35 and consequently results in the increase of exchange reactivity. This In previous studies on H/D exchange of polyphenol, the site in the middle of two meta hydroxyl group seems to have priority of exchange.…”

Section: Resultsmentioning

confidence: 99%

Isomeric Effect on H/D Exchange of Resveratrol Studied by NMR Spectroscopy

et al. 2010

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Resveratrol (3,5,4'-trihydroxylstilbene), a phytoalexin in response to injury or fungal attack, is found in grapes and other food products. It has been well documented that the compound has beneficial effects as hypolipidemic, anticancer, antiviral, neuroprotective, antiaging, and anti-inflammatory natural active principle. It was observed that both trans-and cis-resveratrols undergo hydrogen-deuterium (H/D) exchange at H-2,6 and H-4 positions of the A-ring. The exchange rates were determined by 1 H NMR spectroscopy. The results reveal that the exchange rates are configuration and pH dependent. Derivative of 2-O-β-D-glucoside can significantly speed up the H/D exchange reactions for both isomers. The trans-resveratrol experiences faster H/D exchanging than the cis-resveratrol. Such isomeric effect is possibly due to the factor that the trans-resveratrol is in favor of forming larger/super conjugative system and has less spatial interference. Theoretical calculation shows that electronegativity at these positions is in the order of H-2,6＞H-4, which is in consistent with the exchange rates observed by NMR. The results may be of help in understanding the properties of resveratrol, and in analysis of resveratrol in natural products or body fluids using mass spectroscopy that occasionally requires stable deuterium isotope labeling.

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Section: Resultsmentioning

confidence: 99%

Isomeric Effect on H/D Exchange of Resveratrol Studied by NMR Spectroscopy

et al. 2010

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“…At pH 2 11 .O, there were two absorption bands (350 and 415 nm), and purpurogallin was further oxidized. Phloroglucinol had an absorption band at 275 nm at pH 8.0, and phloroglucinol dissociated partly to monodeprotonated anion (15,16). At pH 1 11.0, there were two absorption bands at 250 and 350 nm, and phloroglucinol existed in keto-dianion form (l5, 16).…”

Section: Uv-visible Absorption Spectramentioning

confidence: 99%

“…Phloroglucinol had an absorption band at 275 nm at pH 8.0, and phloroglucinol dissociated partly to monodeprotonated anion (15,16). At pH 1 11.0, there were two absorption bands at 250 and 350 nm, and phloroglucinol existed in keto-dianion form (l5, 16). At pH 8.9, it was a mixture of undissociated molecules, monoanion and dianion (15,16).…”

Section: Uv-visible Absorption Spectramentioning

confidence: 99%

Effect of pH on Inhibition and Enhancement of Luminol–H2O2–Co2+ Chemiluminescence by Phenolic Compounds and Amino Acids

Cui

Shi

Rong

et al. 2004

Photochem Photobiol

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The effect of pH on inhibition and enhancement of luminol-H2O2-Co2+ chemiluminescence (CL) by 18 phenolic compounds and 20 amino acids was studied. It was found that most of the tested compounds showed an inhibiting effect at lower pH and an enhancing effect at higher pH. At a midrange pH, for some phenolic compounds with two ortho-position -OH, both an inhibiting and an enhancing peak were simultaneously observed. UV-visible spectra of the tested phenolic compounds at different pH values were studied. The mechanism for CL inhibition and enhancement was proposed. It is likely that the competition of the -OH or the -NH2 group and other reducing groups in the molecules with luminol for O2*- led to the CL inhibition. A reaction of -COO(-) and quinone or ketone formed by phenolic compounds at higher pH via deprotonation with O2*- also resulted in the CL enhancement.

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“…[2][3][4][5] Thea naerobic degradation of 1 into dihydrophloroglucinol (2)requires an initial NADPH-dependent reduction, which is followed by ah ydrolytic ring cleavage (Scheme 1). [7] Such biocatalytic dearomatization reactions are frequently found in the bio-synthesis of secondary metabolites as at ool for deoxygenation, which in this case would result in resorcinol (3; Scheme 2). [6] Indeed, Lohrie and Knoche reported up to 10 tautomeric forms of 1 in aqueous solution.…”

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confidence: 99%

“…[6] Indeed, Lohrie and Knoche reported up to 10 tautomeric forms of 1 in aqueous solution. [7] Such biocatalytic dearomatization reactions are frequently found in the bio-synthesis of secondary metabolites as at ool for deoxygenation, which in this case would result in resorcinol (3; Scheme 2). [8] Patel et al have shown the NADPH-dependent reduction of 1 into 2 by ap artially purified phloroglucinol reductase (PGR) from Coprococcus sp., which has am olecular weight of about 130 kDa.…”

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Biocatalytic Properties and Structural Analysis of Phloroglucinol Reductases

et al. 2016

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Phloroglucinol reductases (PGRs) are involved in anaerobic degradation in bacteria, in which they catalyze the dearomatization of phloroglucinol into dihydrophloroglucinol. We identified three PGRs, from different bacterial species, that are members of the family of NAD(P)H-dependent short-chain dehydrogenases/reductases (SDRs). In addition to catalyzing the reduction of the physiological substrate, the three enzymes exhibit activity towards 2,4,6-trihydroxybenzaldehyde, 2,4,6-trihydroxyacetophenone, and methyl 2,4,6-trihydroxybenzoate. Structural elucidation of PGRcl and comparison to known SDRs revealed a high degree of conservation. Several amino acid positions were identified as being conserved within the PGR subfamily and might be involved in substrate differentiation. The results enable the enzymatic dearomatization of monoaromatic phenol derivatives and provide insight into the functional diversity that may be found in families of enzymes displaying a high degree of structural homology.

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Dissociation and keto-enol tautomerism of phloroglucinol and its anions in aqueous solution

Cited by 29 publications

References 0 publications

Isomeric Effect on H/D Exchange of Resveratrol Studied by NMR Spectroscopy

Isomeric Effect on H/D Exchange of Resveratrol Studied by NMR Spectroscopy

Effect of pH on Inhibition and Enhancement of Luminol–H2O2–Co2+ Chemiluminescence by Phenolic Compounds and Amino Acids

Biocatalytic Properties and Structural Analysis of Phloroglucinol Reductases

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