Quassinoids with Inhibitory Activities against Plant Fungal Pathogens from <i>Picrasma javanica</i>

Abstract

A bioactivity-guided study on the leaves of <i>Picrasma javanica</i> led to the isolation of 19 quassinoids, including 13 new compounds. The structures of the new compounds were elucidated by a combination of spectroscopic data analysis, X-ray crystallography studies, and electronic circular dichroism (ECD) data interpretation. Compounds <b>1</b>-<b>7</b> are rare examples of quassinoids with a keto carbonyl group at C-12. The biological activities of 11 of the more abundant isolates were evaluated against five phytopathogenic fungi in vitro, and several of them including <b>6</b> and <b>15</b> showed moderate inhibitory effects that were comparative to those of the positive control, carbendazim. In addition, the preliminary structure-activity relationships (SARs) of these quassinoids were also investigated.