To probe the importance of physicochemical properties and biochemical interactions on Ndh2-dependent EET in L. plantarum, a library of quinones, consisting of naphthoquinones (1 -29), anthraquinones (30 -34), and benzoquinones (35 -40), was designed by drawing inspiration from natural small molecules with known electron shuttling properties. A subset of the quinones were obtained through commercial or natural sources (Fig. ). Chimaphilin (6) and hydroxy-chimaphilin (7) were isolated from lyophilized Chimaphila umbellata bark (Fig. ). Compounds 8 -11 are produced by the Pau D'Arco (Tabebuia impetiginosa) tree, but the purification proved challenging, so they were purchased for this study. Quinones 16 -29 were obtained through semi-synthesis as part of this study (Schemes 1 and 2; Fig. ). Our synthetic efforts were focused on diversifying 1,4-naphthoquinones, specifically adding functionality to the unoccupied 3-position of menadione ( ) or the unoccupied 2-and 3-positions of naphthoquinone (15), as these positions are in conjugation with the quinone functionality and are therefore hypothesized to have the largest impact on EET activity. In addition to the naphthoquinones, structurally diverse anthraquinones (30 -34) and benzoquinones (35 -40) were acquired through commercial sources.