Competitive inhibition of mushroom tyrosinase by 4-substituted benzaldehydes.
ABSTRACT A kinetic study of the inhibition of mushroom tyrosinase by 4-substituted benzaldehydes showed that these compounds behave as classical competitive inhibitors, inhibiting the oxidation of L-3,4-dihydroxyphenylalanine (L-DOPA) by mushroom tyrosinase (o-diphenolase activity). The kinetic parameter (K(I)) characterizing this inhibition was evaluated for all of the seven compounds assayed. Cuminaldehyde showed the most potent inhibitory activity (K(I) = 9 microM). It also inhibited the oxidation of L-tyrosine by mushroom tyrosinase (o-monophenolase activity) in a competitive manner. The corresponding kinetic parameter for this inhibition was evaluated (K(I) = 0.12 mM).
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ABSTRACT: The aim of the present study is to preliminarily investigate the antimelanogenesis effect of Inonotus obliquus extracts by cell-free mushroom tyrosinase assay. It was found that petroleum ether and n-butanol extracts might contain unknown potential tyrosinase inhibitors, while its ethyl acetate extract might contain some unknown accelerators. Six compounds were isolated and their structures were identified by interpretation of NMR data and nicotinic acid was first discovered in Inonotus obliquus. In cells testing, betulin and trametenolic acid decreased tyrosinase activity and melanin content, while inotodiol and lanosterol significantly increased tyrosinase activity and melanin content, showing an AC50 of 9.74 and 8.43 μM, respectively. Nicotinie acid, 3β,22,25-trihydroxy-lanosta-8-ene, had a little or no effect on tyrosinase. Betulin exhibited a mode of noncompetitive inhibition with a K I = K IS of 0.4 μM on tyrosinase activity showing an IC50 of 5.13 μM and being more effective than kojic acid (6.43 μM), and trametenolic acid exhibited a mode of mixed inhibition with a K I of 0.9 μM, K IS of 0.5 μM, and an IC50 of 7.25 μM. We proposed betulin and trametenolic acid as a new candidate of potent tyrosinase inhibitors and inotodiol and lanosterol as accelerators that could be used as therapeutic agent.Evidence-based Complementary and Alternative Medicine 01/2014; 2014:259836. · 2.18 Impact Factor
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ABSTRACT: The antioxidant capacity of two active papers (based on solid and emulsion paraffin) with cinnamon essential oil was studied. Mushroom samples were introduced in macroperforated PET trays covered with the active papers, and weight loss and browning monitored for 9 days. The antioxidant capacity of the different papers was evaluated based on scavenging 1,1-diphenyl-2-picryl-hydrazyl (DPPH) and tyrosinase inhibition kinetics, and the release of aromatic volatile oils was determined by HSPME–GC–MS. Differences in performance were observed: the active papers were more efficient at avoiding weight loss and mushroom browning when compared to the non-active paraffin-based papers. The efficiency increased when the bottom and walls of the trays were covered rather than the bottom alone. Better results were observed when cinnamon was incorporated as emulsion paraffin instead of a solid.Food Chemistry 03/2015; 170:30–36. · 3.26 Impact Factor
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ABSTRACT: The effects of α-arbutin on the monophenolase and diphenolase activities of mushroom tyrosinase were investigated. The results showed that α-arbutin inhibited monophenolase activity but it activated diphenolase activity. For monophenolase activity, IC50 value was 4.5 mmol·L-1 and 4.18 mmol·L-1 of α-arbutin could extend the lag time from 40.5 s to 167.3 s. Alpha- arbutin is proposed to be regarded as a triphenolic substrate by the enzyme during catalyzation, leading to the suicide inactivation of the active site of tyrosinase. For diphenolase activity, α-arbutin acted as an activator and its activation mechanism was mixed type activation. To reveal such activation, it should be mainly refered to the conformational changes in tyrosinase caused by the interaction of α-arbutin with residues located at the entrance to the active site, and the decrease of the effect of suicide inactivation.PLoS ONE 01/2014; 9(10):e109398. · 3.53 Impact Factor