The Tithonia diversifolia methanolic extract (TDM), which showed antiproliferative activity against human
glioblastoma U373 cells, with an IC50 value of 59.2±3.7 μg mL(-1), was passed through
silica gel chromatography and successively eluted with different percentages of EtOAc/
hexane. The 10-60% EtOAc/
hexane subfractions, which exhibited a comparatively higher antiproliferative activity, were isolated, and then structural identification was proceeded with 1H nuclear magnetic resonance. The isolated compound was
tagitinin C, a kind of
sesquiterpenoid. The IC50 value was 6.1±0.1 μg mL(-1) in U373 treated with
tagitinin C. In flow cytometric analysis and inhibition of pan-
caspase, the results showed that the anti-
glioblastoma effect was apoptosis-independent. In PARP, p-p38, ULK1, and LC3-II expression, the anti-
glioblastoma induced by
tagitinin C was likely via autophagy. In the ULK1
siRNA transfection experiment, autophagy blockade counteracted the suppression induced by
tagitinin C. The result suggested that
tagitinin C induces U373 cell death dependent upon autophagy under certain conditions.