Flavonols from Heterotheca inuloides: tyrosinase inhibitory activity and structural criteria.
Tyrosinase inhibitory activity of flavonols, galangin, kaempferol and quercetin, was found to come from their ability to chelate copper in the enzyme. In contrast, the corresponding flavones, chrysin. apigenin and luteolin, did not chelate copper in the enzyme. The chelation mechanism seems to be specific to flavonols as long as the 3-hydroxyl group is free. Interestingly, flavonols affect the enzyme activity in different ways. For example, quercetin behaves as a cofactor and does not inhibit monophenolase activity. On the other hand, galangin inhibits monophenolase activity and does not act as a cofactor. Kaempferol neither acts as a cofactor nor inhibits monophenolase activity. However, these three flavonols are common to inhibit diphenolase activity by chelating copper in the enzyme.
Kubo
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I
Department of Environmental Science, Policy and Management, University of California, Berkeley 94720-3112, USA. ikubo@uclink4.berkeley.edu
Kinst-Hori
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I
Chaudhuri
S K
SK
Kubo
Y
Y
Sánchez
Y
Y
Ogura
T
T
D018650:Arnica / Q000737:chemistry; D001665:Binding Sites; D004156:Catechol Oxidase / Q000037:antagonists & inhibitors / Q000737:chemistry; D002614:Chelating Agents / Q000378:metabolism / Q000494:pharmacology; D003300:Copper / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000378:metabolism / Q000494:pharmacology; D044950:Flavanones; D047309:Flavones; D005419:Flavonoids / Q000378:metabolism / Q000494:pharmacology*; D044948:Flavonols; D005656:Fungal Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry; D020128:Inhibitory Concentration 50; D044949:Kaempferols; D007700:Kinetics; D007980:Levodopa / Q000378:metabolism; D014442:Monophenol Monooxygenase / Q000037:antagonists & inhibitors* / Q000737:chemistry; D010084:Oxidation-Reduction; D010936:Plant Extracts / Q000737:chemistry; D010946:Plants, Medicinal; D011794:Quercetin / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D013053:Spectrophotometry; D013329:Structure-Activity Relationship
D002614:Chelating Agents; D004791:Enzyme Inhibitors; D044950:Flavanones; D047309:Flavones; D005419:Flavonoids; D044948:Flavonols; D005656:Fungal Proteins; D044949:Kaempferols; D010936:Plant Extracts; C037032:galangin; D007980:Levodopa; C006680:baicalein; C006552:kaempferol; D003300:Copper; D011794:Quercetin; D004156:Catechol Oxidase; D014442:Monophenol Monooxygenase; C043562:flavone