Rupichrysenoids A-H, phytocannabinoid-like meroterpenoids from Rhododendron rupicola var. chryseum: Isolation, structure, and bioactivity.

The first phytochemical investigation on the aerial parts of Rhododendron rupicola var. Chryseum led to the discovery of eight previously undescribed phytocannabinoid-like meroterpenoids (PLMs), named rupichrysenoids A-H (1-8), along with two previously reported ones (9 and 10). The structural establishment of PLMs 1-8 was achieved by means of spectroscopic data (NMR and HRMS) analysis, ECD calculations, and single crystal X-ray diffraction, as well as NMR calculations and DP4+ probability analyses. PLMs 2 and 10 showed significant α-glucosidase inhibitory effects with IC50 values of 16.73 ± 1.07 and 27.94 ± 1.08 μM, respectively. Molecular docking studies uncovered that the formation of hydrogen bonds of PLMs 2 and 10 with residues Lys-150, Pro-312, and Leu-313 of α-glucosidase might play crucial roles in their bioactive effects. In addition, PLM 10 exhibited significant antibacterial activities against MRSA (methicillin-resistant Staphylococcus aureus) and VRE (vancomycin-resistant Enterococci) with MIC value of both 2 μg/mL. These findings could provide potential candidates for the further development of antidiabetic and antibacterial agents.