Two New Limonoids from the Root Bark of Chinese Medicinal Plant Dictamnus dasycarpus

Two new limonoids, kihadanin C (1) and 23‐methoxydasylactone A (2), together with seven related known ones, 3–9, were isolated from the root bark of the plant Dictamnus dasycarpus. The structures of the new compounds were elucidated on the basis of extensive analyses of their spectroscopic data (1D‐ and 2D‐NMR, MS) and by comparison of their NMR data with those reported in the literature. To the best of our knowledge, 1 presents the first example of A,D‐seco limonoid with an unusual 3,4‐dihydroxy‐2,5‐dimethoxytetrahydrofuran moiety as ring E. In the bioassay in vitro, 7 showed moderate antibacterial activity against Staphylococcus aureus, while 8 and 9 displayed neuroprotective activities against H2O2‐induced injury in SH‐SY5Y cells.