Three new secoiridoid glycoside dimers from Swertia mileensis

Structural characterization and anti-oxidation activity of pectic polysaccharides from Swertia mileensis

In this study, we isolated the pectic polysaccharide WSMP-A2b (37 kDa) from the stems and leaves of Swertia mileensis, and we investigated its compositional/structural features and antioxidant activity. FT-IR, NMR, monosaccharide composition, enzymatic hydrolysis and methylation analyses indicated that WSMP-A2b is composed of rhamnogalacturonan I (RG-I), rhamnogalacturonan II (RG-II) and homogalacturonan (HG) domains with mass ratios of 2.1:1.0:2.2. The RG-I domain is primarily substituted with α-L-1,5-arabinan and type II arabinogalactan (AG-II) side chains, as well as minor contributions of β-D-1,4-galactan and/or type I arabinogalactan (AG-I) side chains. The HG domain was released in the form of un-esterified and partly methyl-esterified and/or acetyl-esterified oligogalacturonides with a 1 to 7 degree of polymerization after endo-polygalacturonase degradation. WSMP-A2b showed stronger antioxidant activity in vitro, in part this might due to the presence of galacturonic acid (GalA). In addition, WSMP-A2b exerted a protective effect on tert-butyl hydroperoxide (tBHP)-induced oxidative stress in INS-1 cells by reducing reactive oxygen species (ROS) production and increasing the glutathione/oxidized glutathione (GSH/GSSG) ratio. Our results provide crucial structural information on this pectic polysaccharide from Swertia mileensis, thus prompting further investigation into its structure-activity relationship.

The Progress of Anti-HBV Constituents from Medicinal Plants in China

Hepatitis B virus (HBV) infection causing acute and chronic hepatitis is a serious problem worldwide, whereas the current treatment methods are unsatisfactory. Traditional Chinese herbs that have long been used for medicinal purposes are fascinating sources for novel anti-HBV candidates. This paper summarizes the progress of anti-HBV constituents from diverse medicinal plants in China to provide information for searching new anti-HBV drugs from natural sources.

Phytochemistry and Pharmacological Activities of the Genus Swertia (Gentianaceae): A Review

Swertia plants have been considered to be medicinal plants useful for the treatment of various ailments for thousands of years, especially in Asian countries. This is due to the broad variety of chemical compounds that provide multiple ligands for bonding to different endogenous biomacromolecules for patients. Chemical constituents and pharmacological activities of Swertia plants are summarized in this paper. Approximately 419 metabolites and 40 bioactive compounds have been reported from 30 Swertia species, including xanthones, flavonoids, seco-iridiods, iridiods, triterpenoids, alkaloids, volatiles, and other secondary metabolites. The bioactivities of Swertia plants include anticarcinogenic, hepatoprotective, anti-oxidant, hypoglycemic, anthelmintic, antibacterial, antifungal, anti-diabetic, gut, and airways modulatory, metabolizing isozymes inhibitory, neuroprotective, HIV-I reverse transcriptases inhibitory, anticholinergic, and CNS-depressant activities, etc. In addition, biosynthetic pathways of xanthones, and seco-iridiods, two most important secondary metabolites for Swertia, are elucidated. The xanthones biosynthetic pathway is a mixed biosynthetic pathway involved the shikimate and the malonate routes, and the seco-iridoid pathway starts with geraniol derived from IPP which is produced either via the MEP or the MVA pathway. This review will offer a reference for future researches on the protection of natural resources, the investigation of therapeutic basis, new drug development, and so forth. Metabolic pathways of some crucial active compounds were also discussed in this review.

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

Eleven new secoiridoid aglycones involving unusual C₉-skeleton: swerimilegenins A-F (1–6); bis-C9-skeleton: swerimilegenin G (7); and C₁₀-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.

Anti-hepatitis B virus active secoiridoids from Swertia kouitchensis

Three new secoiridoids, swertiakoulactone (1) and swertiakosides A and B (2 and 3), were isolated from Swertia kouitchensis. Their structures were elucidated by comprehensive spectroscopic analyses including MS, IR, 1D and 2D NMR data. By the anti-hepatitis B virus (HBV) assay on Hep G 2.2.15 cells line in vitro, compound 1 showed moderate activities inhibiting the HBsAg secretion (IC₅₀ = 1.10 mM, SI = 4.39) and HBV DNA replication (IC₅₀ = 1.16 mM, SI = 4.12).

Swerilactones L-O, secoiridoids with C₁₂ and C₁₃ skeletons from Swertia mileensis

Swerilactones L-O (1-4), four unusual secoiridoids with unprecedented C₁₂ and C₁₃ skeletons, were isolated from the traditional Chinese herb Swertia mileensis. Compounds 1 and 2 had moderate inhibitory activities against the secretion of hepatitis B virus surface antigen (IC₅₀ = 1.47 and 1.20 mM, with SI < 1 and 1.53, respectively) and hepatitis B virus e antigen (IC₅₀ = 0.88 and >2.69 mM, with SI 1.62 and <1, respectively) in an antihepatitis B virus assay on the Hep G 2.2.15 cell line in vitro.

Anti-hepatitis B virus active lactones from the traditional Chinese herb: Swertia mileensis

Swerilactones H-K (1-4), which are four novel lactones with an unprecedented C29 skeleton, were isolated from Swertia mileensis (Qing-Ye-Dan), an endemic Chinese herb used for treating viral hepatitis. Their structures were determined by extensive spectroscopic and X-ray crystallographic diffraction analyses. Swerilactones H-K exhibit potent anti-hepatitis B virus activity against HBV DNA replication with IC(50) values ranging from 1.53 to 5.34 μM. For the first time, a plausible biogenetic pathway for swerilactones H-K, together with the previously reported swerilactones A-D is proposed. From a biogenetic point of view, swerilactones A-D are ascribed as secoiridoid dimers, and swerilactones H-K as secoiridoid trimers.