834918-75-1

Upstream product

• 18393-49-2 3',4',7-trihydroxyflavylium chloride 
• 1131-62-0 1-(3,4-dimethoxyphenyl)ethanone 
• 613-45-6 2,4-Dimethoxybenzaldehyde 
• 100753-41-1 (2E)-3-(2,4-dimethoxyphenyl)-1-(3,4-dimethoxyphenyl)prop-2-en-1-one 

Relevant academic research and scientific papers

Analogs of anthocyanins with a 3′,4′-dihydroxy substitution: Synthesis and investigation of their acid-base, hydration, metal binding and hydrogen-donating properties in aqueous solution

Glycosides of hydroxylated flavylium ions are proposed as pertinent analogs of anthocyanins, a major class of polyphenolic plant pigments. Anthocyanins with a 3′,4′-dihydroxy substitution on the B-ring (catechol nucleus) are especially important for their metal chelating and electron-donating (antioxidant) capacities. In this work, an efficient chemical synthesis of 3′,4′-dihydroxy-7-O-β-d-glucopyranosyloxyflavylium chloride and its aglycone is reported. Then, the ability of the two pigments to undergo proton transfer (formation of colored quinonoid bases) and add water (formation of a colorless chalcone) is investigated: at equilibrium the colored quinonoid bases (kinetic products) are present in very minor concentrations (3+, the Al3+-glucoside complex is more stable than the Al3+-aglycone complex due to the higher sensitivity of the latter to water addition and conversion into the corresponding chalcone. Finally, the glucopyranosyloxyflavylium ion and its aglycone are compared for their ability to reduce the 1,1-diphenyl-2-picrylhydrazyl radical in a mildly acidic water/MeOH (1:1) mixture as a first evaluation of their antioxidant activity. Glycosidation at C7-OH results in a lower rate constant of first electron transfer to DPPH and a lower stoichiometry (total number of 1,1-diphenyl-2-picrylhydrazyl radicals reduced per pigment molecule). Anthocyanins are difficult to extract from plants in substantial amount. However, the analogs investigated in this work are of easy access by chemical synthesis and express the physico-chemical properties typical of anthocyanins. They can thus be regarded as valuable models for investigating the coloring, metal-binding and antioxidant properties of these important natural pigments.

Chalcones as potent tyrosinase inhibitors: The importance of a 2,4-substituted resorcinol moiety

Chalcones with tetra-substituted hydroxyl groups were synthesized and tested as tyrosinase inhibitors towards designing novel whitening agents, resulting with the most potent inhibitor, with IC50 of 0.02 μM concn. Compounds, which inhibit tyrosinase, could be effective as depigmenting agents. We have introduced a group of mono-, di-, tri- and tetra-substituted hydroxychalcones as effective tyrosinase inhibitors, showing that the most important factor determining tyrosinase inhibition efficiency is the position of the hydroxyl group(s) rather their number. The aim of the present study was to investigate the contribution of the different functional groups of the tetrahydroxychalcones to their inhibitory potency, with a view to optimizing the design of whitening agents. Four tetrahydroxychalcones were evaluated, the commercially available Butein and other three were synthesized, and their inhibitory effect on tyrosinase was tested. Results showed that a 2,4-substituted resorcinol subunit on ring B contributed the most to inhibitory potency. Changing the resorcinol substitute to position 3,5- or placing it on ring A significantly diminished the inhibitory effect of the compounds. A catechol subunit on ring A acted as a metal chelator (in the presence of copper ions) and as a competitive inhibitor (in the presence of tyrosinase), while a catechol on ring B oxidized to o-quinone (in the presence of both copper ions and tyrosinase). Three of the compounds also demonstrated antioxidant activity, which may contribute to the prevention of pigmentation. An examination of correlations between inhibitory activity and physical properties of the chalcones tested (such as dissociation energy and molecular planarity) showed positive correlation with the moment dipole value in the Y-axis, which may be used as an indicator of the inhibitory potential of new molecules. The present study revealed two very active tyrosinase inhibitors, 2,4,3′,4′- hydroxychalcone and 2,4,2′,4′-hydroxychalcone (with IC50 of 0.2 and 0.02 μM, respectively). Structure-related activity studies added some understanding of the role and contribution of different functional groups associated with tyrosinase inhibitors.