Abstract
Glutathione ( GSH) undergoes facile electron transfer with vanadium( V)- substituted Keggin- type heteropolyoxometalates, [(PVW11O40)-W-V](4-) (HPA1) and [PVV - (VW10O40)-W-V](5-) (HPA2). The kinetics of these reactions have been investigated in phthalate buffers spectrophotometrically at 25 degrees C in aqueous medium. One mole of HPA1 consumes one mole of GSH and the product is the oneelectron reduced heteropoly blue, [(PVW11O40)-W-IV] (5-). But in the GSH- HPA2 reaction, one mole of HPA2 consumes two moles of GSH and gives the two- electron reduced heteropoly blue [(PVVW10O40)-V-IV-W-IV](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 (+)], 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 [(PVVVW9O40)-V-V-V-V-W-V](6-) (HPA3) against MRSA were tested in vitro in combination with vancomycin and penicillin G. The HPAs sensitize MRSA towards penicillin