Acetohydroxyacid Synthase (AHAS) Inhibitor-Based Commercial Sulfonylurea Herbicides as Glutathione Reductase Inhibitors: in Vitro and in Silico Studies

In this study, in vitro inhibitory effect of AHAS inhibiting-based commercial sulfonylurea herbicides on human GR and S. cerevisiae GR was determined by electrochemical method. Our findings, the first report in literature, show that the four commercial herbicides were found to be the inhibitors in the range of 4.90–9.75 μM for ScGR, and in the range of 8.54–18.84 μM for hGR. Global reactivity descriptors (energy gaps, electronegativity, hardness and electrophilicity index) of the herbicides were calculated by DFT/B3LYP/6-31G(d,p) method in gas phase. The electrochemical behavior of the herbicides was studied by cyclic voltammetry. Single-electron half-wave reduction potentials and global reactivity descriptors were correlated with the IC50 values of the herbicides. Molecular docking analysis using Schrödinger Suite was applied to examine the interaction between the herbicides and human GR (PDB ID:1XAN and 2GH5), S. cerevisiae GR (PDB ID:2HQM), P. falciparum GR (PDB ID:1ONF), C. albicans AHAS (PDB ID:6DEL) and ScAHAS (PDB ID: 5FEM. Based on the docking results, it can be predicted that (a) herbicides have similar binding potential to two different binding sites of hGRs, (b) herbicides may have antimalarial potential against P. falciparum (c) herbicides may have antifungal potential against C. albicans. © 2022 Wiley-VCH GmbH

Effects of Novel Photosynthetic Inhibitor [CuL₂]Br₂ Complex on Photosystem II Activity in Spinach

The effects of the novel [CuL2]Br2 complex (L = bis{4H-1,3,5-triazino [2,1-b]benzothiazole-2-amine,4-(2-imidazole)}copper(II) bromide complex) on the photosystem II (PSII) activity of PSII membranes isolated from spinach were studied. The absence of photosynthetic oxygen evolution by PSII membranes without artificial electron acceptors, but in the presence of [CuL2]Br2, has shown that it is not able to act as a PSII electron acceptor. In the presence of artificial electron acceptors, [CuL2]Br2 inhibits photosynthetic oxygen evolution. [CuL2]Br2 also suppresses the photoinduced changes of the PSII chlorophyll fluorescence yield (FV) related to the photoreduction of the primary quinone electron acceptor, QA. The inhibition of both characteristic PSII reactions depends on [CuL2]Br2 concentration. At all studied concentrations of [CuL2]Br2, the decrease in the FM level occurs exclusively due to a decrease in Fv. [CuL2]Br2 causes neither changes in the F0 level nor the retardation of the photoinduced rise in FM, which characterizes the efficiency of the electron supply from the donor-side components to QA through the PSII reaction center (RC). Artificial electron donors (sodium ascorbate, DPC, Mn2+) do not cancel the inhibitory effect of [CuL2]Br2. The dependences of the inhibitory efficiency of the studied reactions of PSII on [CuL2]Br2 complex concentration practically coincide. The inhibition constant Ki is about 16 µM, and logKi is 4.8. As [CuL2]Br2 does not change the aromatic amino acids’ intrinsic fluorescence of the PSII protein components, it can be proposed that [CuL2]Br2 has no significant effect on the native state of PSII proteins. The results obtained in the present study are compared to the literature data concerning the inhibitory effects of PSII Cu(II) aqua ions and Cu(II)-organic complexes