Discovery of a nonsteroidal brassinolide-like compound, NSBR1.

Fourteen compounds screened from 5 million compounds were submitted to bioassay to find brassinolide (BL) agonists/antagonists against . Of these, two -benzoyl-'-phenylpiperazine (NBNPP)-type compounds showed antagonistic activity; however, none showed agonistic activity against . The substituents at the benzoyl moiety of NBNPP were changed to OH groups to derive -(3,4-dihydroxybenzoyl)-'-(4-butanoyl-2-fluorophenyl)pyrazine, which was named NSBR1. NSBR1 was rationally designed based on docking simulations and molecular dynamics. NSBR1 significantly suppressed the gene expression of and , which are known as marker genes for the action of BL. This novel NSBR1 was also effective in the rice lamina inclination assay (RLIA), and the activity in terms of the 50% effective dose (ED) was determined as 0.79 nmol/plant from the dose-response curve for RLIA.