Inhibitory effect of coumarin derivatives on apple (cv. Idared) polyphenol oxidase

• Published in: Croatian journal of food science and technology Vol. 9; no. 1; pp. 57 - 65
• Main Authors: Strelec, I., Buric, P., Jankovic, Irena, Kovac, T., Molnar, Maja
• Format: Journal Article Paper
• Language: English
• Published: Prehrambeno-tehnološki fakultet Osijek 07.06.2017; Josip Juraj Strossmayer University of Osijek, Faculty of Food Technology Osijek
• Subjects: apple polyphenol oxidase; coumarin derivatives; inhibition
• ISSN: 1847-3466; 1848-9923
• DOI: 10.17508/CJFST.2017.9.1.08

Inhibitory effect of 32 coumarin derivatives (20 Schiff bases, 5 thiosemicarbazides, 5 thiazolidinones, and their precursors, 7-hydroxy-4-methylcoumarin and 4-methylcoumarin-7-yl hydrazine carboxylate) on partially purified apple polyphenol oxidase was investigated. Thirteen coumarin derivatives inhibited polyphenol oxidase (5 Schiff bases, 5 thiosemicarbazides, 1 thiazolidinone, 4-methyl-7-hydroxycoumarin and 4-methylcoumarin-7-yl hydrazine carboxylate), while 19 derivatives showed no effect on enzyme activity. The most effective inhibitors were thiosemicarbazides, with 4-methyl-1-(2-(4-methyl-2-oxo-2H-chromen-7-yloxy)acetyl) thiosemicarbazide (compound C23) being the most prominent inhibitor (IC50 = 10.45 µM). The importance of thiosemicarbazide moiety as crucial structure element for strong apple PPO inhibition was confirmed by its cyclisation to thiazolidinone bearing the same substituents as corresponding thiosemicarbazide. Capture of the sulphur atom of thiosemicarbazide group within tiazolidinone ring caused significant loss of inhibitory effect against apple PPO.