Antimicrobial alkaloids from the root bark of Dictamnus dasycarpus

Two new furoquinoline alkaloids, named 1'-oxo-isoplatydesmine (1) and demethoxyacrophylline (2), as well as 11 known alkaloids (3-13) were isolated from the root bark of Dictamnus dasycarpus Turcz. The structures of 1 and 2 were established by detailed spectroscopic elucidation, such as 1 D & 2 D NMR and HRMS, etc. The unexpected autoracemization of 1 was discussed based on the stereochemistry of reported dihydrofuroquinolines. Compounds 3-5 exhibited moderate inhibitory activities against Bacillus subtilis, Candida albicans, and Pseudomonas aeruginosa with MICs 32-64 μg/ml, revealing the active principles of D. dasycarpus for treating skin diseases in its traditional usage.