Protein Tyrosine Phosphatase 1B Inhibitory Iridoids from .

Phytochemical investigation of the leaves and bark of has led to the isolation of six new iridoids, subcordatanols I-V (- and ) and 1--methylcrescentin I (), along with two known analogues ( and ). Among them, subcordatanol I () is the first example of a 3,8-monoepoxy-iridoid featuring a caged 2-oxa-bicyclo[3.2.1]octane core. The absolute stereochemistry at C-4 of , , and was established through their acid-catalyzed reaction products subcordatalactones A (), B (), and C (), respectively. Subcordatanols I () and II (), as well as subcordatalactones A () and B (), displayed inhibitory activity against protein tyrosine phosphatase 1B (PTP1B). Enzyme kinetic studies indicated that and are competitive inhibitors. A molecular docking study is also reported.