Dipasperoside B, a New Trisiridoid Glucoside from Dipsacus asper

Dipasperoside B (1), isolated from the root of Dipsacus asper, was determined to be a first example of naturally occurring iridoid glucoside trimer with an unusual skeleton featuring oxaloacetic acid derived moiety coupled with a secoiridoid nucleus in the central part, on the basis of spectroscopic data. Dipasperoside B (1) revealed the inhibitory activity against nitric oxide (NO) production in a lipopolysaccharide (LPS)-activated murine macrophage RAW264.7 cell line, with an IC₅₀ value of 21.3 μM, identical to a positive control, N(G)-monomethyl-L-arginine (L-NMMA, IC₅₀ 22.6 μM), without any significant cytotoxicity.