Vanadium(V)-substituted Keggin-type heteropolyoxotungstophosphates as electron transfer and antimicrobial agents: oxidation of glutathione and sensitization of MRSA towards [beta]-lactam antibiotics

• Published in: Transition metal chemistry (Weinheim) Vol. 35; no. 8; p. 1019
• Main Authors: Sami, Ponnusamy, Anand, Thangarajan Durai, Premanathan, Mariappan, Rajasekaran, Kasi
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Nature B.V 01.11.2010
• ISSN: 0340-4285; 1572-901X
• DOI: 10.1007/s11243-010-9425-3

Glutathione (GSH) undergoes facile electron transfer with vanadium(V)-substituted Keggin-type heteropolyoxometalates, [ PV V W 1 1 O 4 0 ] 4 − (HPA1) and [ PV V V V W 1 0 O 4 0 ] 5 − (HPA2). The kinetics of these reactions have been investigated in phthalate buffers spectrophotometrically at 25 °C in aqueous medium. One mole of HPA1 consumes one mole of GSH and the product is the one-electron reduced heteropoly blue, [ PV IV W 1 1 O 40 ] 5 − . But in the GSH-HPA2 reaction, one mole of HPA2 consumes two moles of GSH and gives the two-electron reduced heteropoly blue [ PV IV V IV W 10 O 40 ] 7 − . Both reactions show overall third-order kinetics. At constant pH, the order with respect to both [HPA] species is one and order with respect to [GSH] is two. At constant [GSH], the rate shows inverse dependence on [H^sup +^], suggesting participation of the deprotonated thiol group of GSH in the reaction. A suitable mechanism has been proposed and a rate law for the title reaction is derived. The antimicrobial activities of HPA1, HPA2 and [ PV V V V V V W 9 O 4 0 ] 6 − (HPA3) against MRSA were tested in vitro in combination with vancomycin and penicillin G. The HPAs sensitize MRSA towards penicillin G.[PUBLICATION ABSTRACT]