Identification of antibacterial constituents from Planch with an activity-guided method.

Bacterial infections and antibiotic resistance pose significant public health challenges globally. Natural products serve as valuable sources for discovering antimicrobial agents. Planch, a folk medicine, is traditionally used to treat various inflammatory diseases. In this study, we investigated the antibacterial metabolites derived from Planch. Rhodosimsiin A (1), bearing a 1,5--1,6 and 3,6-epoxy grayanane diterpene skeleton, representing a novel 5/6/7/6/5 pentacyclic ring system, and 3,16-dihydroxy-6-ethoxy-14-acetoxy-grayan-1(5)-ene-10-one (4), which represents the first example of the degradation of C-20 and carbonylation in C-10 diterpenoid, together with two new grayanane diterpenes (2-3), three new triterpenes (13-15), and known analogs (5-12, 16-30), were isolated from the leaves of Planch by using the bioassay-guided method. Their structures were elucidated by comprehensive spectroscopic analyses, and absolute configurations were established by single-crystal X-ray diffraction and calculated ECD spectra. Compounds 14, 15, 18, 20, 27, 28, and 30 exhibited potent antibacterial activity with an MIC of 1.4-24.3 g/mL against . The findings of this research indicate that secondary metabolites derived from . Planch are promising natural antimicrobial candidates.