Polyoxovanadate inhibition of Escherichia coli growth shows a reverse correlation with Ca2+-ATPase inhibition

Recently, a global analysis of the structure-activity-relationship of a series of polyoxometalates (POMs) revealed that the most active POMs were ascribed to be polyoxovanadates (POVs), especially decavanadate (V-10), which was very active against certain bacteria (Bijelic et al., Chem. Commun., 2018). The present study explores this observation and compares the effects of three POVs namely MnV11, MnV13 and V-10 against Escherichia coli growth. It was observed that MnV11 presents the lowest growth inhibition (GI(50)) value for Escherichia coli followed by the MnV13 compound, being about 2 times lower than that of V-10; respectively, the values obtained were 0.21, 0.27 and 0.58 mM. All three compounds were more effective than vanadate alone (GI(50) = 1.1 mM) and also than decaniobate, Nb-10 (GI(50) > 10 mM), an isostructural POM of V-10. However, the POVs exhibiting the highest antibacterial activity (MnV11) were shown to have the lowest Ca2+-ATPase inhibitor capacity (IC50 = 58 mM) whereas decavanadate, which was also very active against this membranar ATPase (IC50 = 15 mM), was less active against bacterial growth, suggesting that POV inhibition of ion pumps might not be associated with the inhibition of Escherichia coli growth.