Minor secoiridoid aglycones from the low-polarity part of the traditional Chinese herb: Swertia mileensis

Eleven new secoiridoid aglycones involving unusual C(9)-skeleton: swerimilegenins A-F (1–6); bis-C9-skeleton: swerimilegenin G (7); and C(10)-skeleton: swerimilegenins H-K (8–11), as well as six known ones, were isolated from the low-polarity part of the traditional Chinese herb medicine Swertia mileensis. Their structures were determined by extensive spectroscopic data and X-ray diffraction. Biogenetically, swerimilegenin A (1) belonged to 10-nor-secoiridoid, and swerimilegenins B-F (2–6) were 1-nor-secoiridoids. Erythrocentaurin (12) and gentiogenal (15) showed moderate anti-HBV activity on HepG 2.2.15 cell line in vitro. [Image: see text] ELECTRONIC SUPPLEMENTARY MATERIAL: Supplementary material is available for this article at 10.1007/s13659-013-0059-y and is accessible for authorized users.