Two new tetrahydroprotoberberine N-oxides, 7R,14S-cis-tetrahydrocoptisine N-oxide (1) and 7R,14R-trans-tetrahydmeoptisine N-oxide (2) along with fourteen known compounds (3-16) were isolated from the aerial parts of Chelidonium mails. Their structures were elucidated by spectroscopic and spectrometric methods, such as 1D and 2D-NMR (HSQC, HMBC, NOESY) and HRESIMS. The absolute configurations of 1 and 2 were established by comparison of their experimental and calculated ECD data. All isolates were evaluated for their inhibitory effects on the nitric oxide production in LPS-induced RAW 264.7 macrophages, and compounds 2, 6-10, 13, and 15 showed significant inhibitory effects with the IC50 values ranging from 1.1-31.9 mu M.