Characteristic alkaloids from Stemona sessilifolia with lung protective effects

[Display omitted] •Four undescribed compounds and a new natural product were identified from Stemona sessilifolia.•UPLC-QTOF/MS method was used to identify the Stemona alkaloids and summarize the fragmentation patterns of mass spectrometry.•This study confirmed the protective effect of Stemona alkaloids on lung injury for the first time.•It was verified that the protective effect of tuberostemonine D on lung injury induced by nm SiO2 was related to the Nrf2 activation. In the research on lung protective effects from the roots of Stemona sessilifolia, twenty-five Stemona alkaloids have been isolated, including four undescribed components (1, 3–5), a new natural product (2) and 20 known alkaloids (6–25). Their structures were analyzed by NMR spectra, high-resolution mass spectrum data, and other chemical methods. UPLC-QTOF/MS method was used to identify the Stemona alkaloids and summarize the fragmentation patterns of mass spectrometry. The lung-protective effects of these compounds were evaluated using MLE-12 cells induced by NNK and nm SiO2. The results showed that compounds 3, 5, 8, 10–11, 17–21 and 23 exhibited protective effects on NNK-induced cell injury. Compounds 2, 8–11, 14, 17–19 and 22 showed improvement in nm SiO2-induced lung epithelial cell injury. Compound 10 (tuberostemonine D), a representative alkaloid with a high content in Stemona sessilifolia, significantly protected C57BL/6 lung injury mice induced by nm SiO2, suggesting it a key component of Stemona alkaloids that play a protective role in lung injury. The results of in vivo activity showed that compound 10 could improve the lung injury of mice, reduce ROS content, and recover the levels of SOD and MDA in serum. Its protective effect on lung injury might be related to Nrf2 activation.