Tussilago farfara is a traditional herbal medicine
used to treat coughs, bronchitis, and asthma. Its bioactive compounds
include sesquiterpenoids with anti-inflammatory, antiproliferative,
neuroprotective, and other effects. Biochemical studies have highlighted
the mechanisms of action, but the investigations of related molecular
pathways have not specified direct molecular targets. Therefore, this
study profiled cellular target proteins of a sesquiterpenoid isolated
from T. farfara using quantitative chemical proteomics
in MDA-MB-231 and MCF-7 human breast cancer cells. Compound 8, 7β-(3′-ethyl-cis-crotonoyloxy)-1α-(2′-methyl
butyryloxy)-3,14-dehydro-Z-notonipetranone, exhibited
potent antiproliferative activity based on its α,β-unsaturated
carbonyl moiety, and its potential cellular target proteins were identified
using a compound 8-based clickable probe. Among >200
identified proteins, 17 showed enrichment ratios of >3 in both
cell
lines, while recombinant 14-3-3 protein zeta and peroxiredoxin-1 were
verified using isothermic calorimetry and their alkylation sites.
Considering the interaction between the α,β-unsaturated
carbonyl moiety of compound 8 and cysteine residues of
the proteins, peptides containing Cys25 and Cys94 of 14-3-3 protein
zeta and Cys83 of peroxiredoxin-1 were significantly reduced by this
sesquiterpene ester. Although the results did not elucidate the effects
of compound 8 in breast cancer cells, identification
of potential target proteins contributes to enhanced understanding
of its antiproliferative and anti-inflammatory effects.