Dipasperoside A, a novel pyridine alkaloid-coupled iridoid glucoside from the roots of Dipsacus asper

A new pyridine alkaloid-coupled iridoid glucoside, dipasperoside A (1), and 20 known compounds (2-21) were isolated from a water extract of Dipsacus asper roots. Compound 1 possessed a unique structural feature with a nicotinic acid nucleus coupled through C-5 with C-7 of a secoiridoid/iridoid glucoside dimer, and esterified with a C-7 hydroxyl group of an iridoid glucoside monomer. All isolates were evaluated for their inhibitory activity against nitric oxide (NO) production in a lipopolysaccharide (LPS)-activated murine macrophage cell line, RAW264.7.