Five undescribed guanidine alkaloids from Plumbago zeylanica

Five undescribed guanidine alkaloids, plumbagines HK (1–4) and plumbagoside E (5), as well as five known analogues (6–10) were isolated from the roots of Plumbago zeylanica. Their structures were established by extensive spectroscopic analyses and chemical methods. In addition, 1–10 were accessed their anti-inflammatory activities by measuring nitric oxide (NO) concentrations in LPS-induced RAW 264.7 cells. However, all compounds especially 1 and 3–5 could not inhibit the secretion of NO but significant increase the secretion of NO. The result reminded us that 1–10 may become potential novel immune potentiators.