Biological evaluation of two Keggin‐type polyoxometalates containing glycine as mushroom tyrosinase inhibitors

Two Keggin-type polyoxometalates (POMs) containing glycine, (HGly)3 PW12 O40 and (HGly)4 SiW12 O40 , were synthesized and evaluated as mushroom tyrosinase inhibitors. The spectrophotometric method results showed that both (HGly)3 PW12 O40 and (HGly)4 SiW12 O40 could strongly inhibit the diphenolase activity of the tyrosinase and that their inhibition mechanisms were reversible. Their half-inhibition concentration values were estimated to be 1.55 and 1.39 mmol/L, respectively. The inhibition kinetics analysis by Lineweaver-Burk plots indicated that (HGly)3 PW12 O40 was an uncompetitive inhibitor with KIS = 0.046 mmol/L, whereas (HGly)4 SiW12 O40 was a noncompetitive inhibitor with KI = KIS = 2.17 mmol/L. This study may help to extend the application of POMs in the fields of medicine and food preservation.