Precise 1H- and 13C-NMR reassignment of dehydrocrebanine by 10-mg INADEQUATE and in silico analysis: With an alert for its toxicity

During our continuous investigation on a Thai traditional medicinal plant, Stephania venosa Spreng, an alkaloid that seemed to be O-methyldehydrobulbocapnine (MDB) or dehydrocrebanine (DC), had been isolated. However, none of the previously reported 1H- and 13C-NMR data for MDB and DC matched our charts. Thus, we herein report the unambiguous determination of the alkaloid structure as DC via a successful INADEQUATE experiment using 10 mg of the unenriched natural specimen as well as an in silico estimation. Furthermore, our biological assay revealed that both the dichloromethane extract of S. venosa and the isolated DC show cytotoxicity to murine macrophage cells, which should be alerted to a folk doctor community that are using S. venosa to treat patients.