- Reactivity assessment of chalcones by a kinetic thiol assay
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The electrophilic nature of chalcones (1,3-diphenylprop-2-en-1-ones) and many other α,β-unsaturated carbonyl compounds is crucial for their biological activity, which is often based on thiol-mediated regulation processes. To better predict their biological activity a simple screening assay for the assessment of the second-order rate constants (k2) in thia-Michael additions was developed. Hence, a clear structure-activity relationship of 16 differentially decorated hydroxy-alkoxychalcones upon addition of cysteamine could be established. Moreover, amongst other naturally occurring α,β-unsaturated carbonyl compounds k2 values for curcumin and cinnamaldehyde were gained while cinnamic acids or esters gave no or very slow reactions.
- Amslinger, Sabine,Al-Rifai, Nafisah,Winter, Katrin,W?rmann, Kilian,Scholz, Rebekka,Baumeister, Paul,Wild, Martin
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- Opening or closing the lock? when reactivity is the key to biological activity
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Thiol-mediated processes play a key role to induce or inhibit inflammation proteins. Tailoring the reactivity of electrophiles can enhance the selectivity to address only certain surface cysteines. Fourteen 2',3,4,4'- tetramethoxychalcones with different α-X substituents (X=H, F, Cl, Br, I, CN, Me, p-NO2-C6H4, Ph, p-OMe-C 6H4, NO2, CF3, COOEt, COOH) were synthesized, containing the potentially electrophilic α,β-unsaturated carbonyl unit. The assessment of their reactivity as electrophiles in thia-Michael additions with cysteamine shows a change in the reactivity of more than six orders of magnitude. Moreover, a clear correlation between their reactivity and an influence on the inflammation proteins heme oxygenase-1 (HO-1) and the inducible NO synthase (iNOS) is demonstrated. As the biologically most active compound, the α-CF3-chalcone is shown to inhibit the NO production in RAW264.7 mouse macrophages in the nanomolar range. More than a million by only one substituent: The direct manipulation of the chemical reactivity of electrophilic agents could be proven for chalcones by simply exchanging the α-hydrogen atom of the α,β-unsaturated carbonyl unit with different substituents (X), leading to a change in reactivity of more than six orders of magnitude for thia-Michael additions with cysteamine, which correlates very well with two electrophile-sensitive biological readouts (see scheme).
- Al-Rifai, Nafisah,Ruecker, Hannelore,Amslinger, Sabine
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p. 15384 - 15395
(2013/11/06)
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