Figure 3.

Isoplumbagin is a substrate of reduced nicotinamide adenine dinucleotide phosphate [NAD(P)H] dehydrogenase quinone 1 (NQO1). (A) The predicted targets of isoplumbagin. (B) The gene ontology term enrichment results of potential binding targets for isoplumbagin based on the Database for Annotation, Visualization, and Integrated Discovery (DAVID) analysis. (C) Schematic representation of isoplumbagin and NQO1 homodimer interaction: i for A and C chains, ii for B and D chains, iii for E and F chains, and iv for G and H chains of NQO1 homodimers. Flavin adenine dinucleotide (FAD) is a cofactor of NQO1. The calculated binding affinity of isoplumbagin and NQO1 homodimer is shown. Hydrogen bonds and van der Waals interactions are shown in stick representation and decorated arc, respectively. (D) The molecular docking between isoplumbagin and the B/D chains of NQO1: Isoplumbagin is colored in white; the NQO1 homodimer is colored in red for chain B and in green for chain D; and FAD is in blue. (E) The NQO1 enzyme activity was calculated in the presence of menadione or isoplumbagin. * Compared with control (no substrate). Data from three independent experiments are presented as mean ± S.E.M. (* p < 0.05, paired Student’s t-test).