Quinones are compounds frequently contained in medicinal plants used for the treatment of inflammatory diseases. Therefore, the impact of plant-derived quinones on the arachidonic acid metabolic pathway is worthy of investigation. In this study, twenty-three quinone compounds of plant origin were tested in vitro for their potential to inhibit leukotriene B4 (LTB4) biosynthesis in activated human neutrophil granulocytes with 5-lipoxygenase (5-LOX) activity. The benzoquinones primin (3) and thymohydroquinone (4) (IC50 = 4.0 and 4.1 microM, respectively) showed activity comparable with the reference inhibitor zileuton (1C50 = 4.1 microM). Moderate activity was observed for the benzoquinone thymoquinone (2) (1C50 = 18.2 microM) and the naphthoquinone shikonin (1) (IC50 = 24.3 microM). The anthraquinone emodin and the naphthoquinone plumbagin (5) displayed only weak activities (IC50 > 50 microM). The binding modes of the active compounds were further evaluated in silico by molecular docking to the human 5-LOX crystal structure. This process supports the biological data and suggested that, although the redox potential is responsible for the quinone's activity on multiple targets, in the case of 5-LOX the molecular structure plays a vital role in the inhibition. The obtained results suggest primin as a promising compound for the development of dual COX-2/5-LOX inhibitors.

Laboratory of Plant Biotechnologies Institute of Experimental Botany AS CR v v i 165 02 Prague 6 Lysolaje Czech Republic