Bupleurum chinense Roots: a Bioactivity-Guided Approach toward Saponin-Type NF-κB Inhibitors

Abstract

The roots of Bupleurum chinense have a long history in traditional medicine to treat infectious diseases and inflammatory disorders. Two major compounds, saikosaponins A and D, were reported to exert potent anti-inflammatory activity by inhibiting NF- κ B. In the present study, we isolated new saikosaponin analogues from the roots of B. chinese interfering with NF- κ B activity in vitro . The methanol-soluble fraction of the dichloromethane extract of Radix Bupleuri was subjected to activity-guided isolation yielding 18 compounds, including triterpenoids and polyacetylenes. Their structures were determined by spectroscopic methods as saikogenin D ( 1 ), prosaikogenin D ( 2 ), saikosaponins B 2 ( 3 ), W ( 4 ), B 1 ( 5 ), Y ( 6 ), D ( 7 ), A ( 8 ), E ( 9 ), B 4 ( 10 ), B 3 ( 11 ), and T ( 12 ), saikodiyne A ( 13 ), D ( 14 ), E ( 15 ) and F ( 16 ), falcarindiol ( 17 ), and 1-linoleoyl-sn-glycero-3-phosphorylcholine ( 18 ). Among them, 4, 15 , and 16 are new compounds, whereas 6, previously described as a semi-synthetic compound, is isolated from a natural source for the first time, and 13 – 17 are the first reports of polyacetylenes from this plant. Nine saponins/triterpenoids were tested for inhibition of NF- κ B signaling in a cell-based NF- κ B-dependent luciferase reporter gene model in vitro . Five of them ( 1, 2, 4, 6 , and 8 ) showed strong (> 50%, at 30 µM) NF- κ B inhibition, but also varying degrees of cytotoxicity, with compounds 1 and 4 (showing no significant cytotoxicity) presenting IC 50 values of 14.0 µM and 14.1 µM in the cell-based assay, respectively.

Facile Synthesis of Saikosaponins

“…The corresponding monosaccharides, named prosaikogenin F (PSF, 3 ) and G (PSG, 4 ) were identified as metabolites of SSa and SSd [ 5 ], which showed hemolytic activity and the absorbability on red blood cells [ 6 , 7 ]. Saikosaponin Y ( 5 ) is likely a biogenetic precursor/product of SSa and SSd, which has a higher oxidation state at C-16; this congener displayed potent cytotoxic and antiviral activities [ 8 , 9 , 10 ]. Monosaccharide 6 , named posaikogenin, was found as an artifact which might be derived from disaccharide 5 .…”

Comprehensive Phytochemical Characterization of Herbal Parts from Kidney Vetch (Anthyllis vulnerariaL.) by LC/MSnand GC/MS

“…For 1D‐ and 2D‐NMR data, see Supporting Information , Scheme S1 , Table S1 . The UV and 13 C‐NMR data correspond to the literature [48–50,59] …”

“…Finally, based on 1D‐ and 2D‐NMR experiments ( 1 H, 13 C, gHMBC, gHSQC, gCOSY) and comparison of 13 C data with the literature the isolated sapogenin could be assigned to saikogenin D ( 76 , Scheme 5, Supporting Information , Table S1 ) [48–50] . However, compared to previous literature we herein report full and detailed 1 H‐signal assignment.…”

“…An isolation of compound 76 from A. vulneraria has not been described so far, but 76 has formerly been detected as an acid hydrolysis artifact of saikosaponins (left structure, Scheme 5), analyzed from roots of Bubleurum chinense and B. falcatum L. These are commonly used as herbal drugs in traditional Chinese medicine (TCM) for the treatment of infectious diseases and inflammatory disorders [47–51] . Interestingly, several saikosaponins and 76 have shown in vitro anti‐inflammatory activity by inhibition of NF‐ κ B [51] .…”

“…An isolation of compound 76 from A. vulneraria has not been described so far, but 76 has formerly been detected as an acid hydrolysis artifact of saikosaponins (left structure, Scheme 5), analyzed from roots of Bubleurum chinense and B. falcatum L. These are commonly used as herbal drugs in traditional Chinese medicine (TCM) for the treatment of infectious diseases and inflammatory disorders. [47][48][49][50][51] Interestingly, several saikosaponins and 76 have shown in vitro antiinflammatory activity by inhibition of NF-кB. [51] According to literature, acidic hydrolysis of the saikosaponins does not only come along with the loss of the sugar moieties, but also with a cleavage of an ether bridge between scaffold atoms C13 and C28, whereby 76 together with its heteroannular diene system is being formed (Scheme 5).…”