NF-κB inhibitory and cytotoxic activities of hexacyclic triterpene acid constituents from Glechoma longituba

Abstract

Background: Non-Small-Cell Lung Cancer (NSCLC) is the most-frequent cause of cancer death, and novel chemotherapeutic drugs for treating NSCLC are urgently needed. 2α, 3α, 23-trihydroxy-13α, 27-cyclours-11-en-28-oic acid (euscaphic acid G) is a new hexacyclic triterpene acid isolated by our group from Glechoma longituba (Nakai) Kupr. However, the underlying mechanisms responsible for the anticancer effects of hexacyclic triterpene acid have not been elucidated.

Purpose: In the present work, we evaluated growth inhibitory effect of the new isolated hexacyclic triterpene acid and explored the underlying molecular mechanisms.

Methods/study designs: Herbs were extracted and constituents were purified by chromatographic separation, including silica gel, ODS, MCI, Sephadex LH-20 and preparative HPLC. The compound structures were elucidated by the use of UV, NMR and MS spectral data. The anticancer activity of euscaphic acid G was evaluated by MTT assay. Cell cycle, apoptosis, reactive oxygen species and mitochondrial membrane potential were determined by flow cytometry. To display the possible mechanism of euscaphic acid G on NCI-H460 cells, RT-PCR, immunofluorescence and Western blot analysis were carried out.

Results: A new hexacyclic triterpene acid, euscaphic acid G, together with fifteen known triterpenoids, was isolated from the aerial parts of G. longituba. Our results showed that euscaphic acid G exerted strong anti-proliferative activity against NCI-H460 cells in a concentration- and time-dependent manner. Flow cytometry demonstrated euscaphic acid G arrested the cell cycle at G1 phase, induced cellular apoptosis, accompanied by ROS generation and mitochondrial membrane potential reduction. Mechanistic studies revealed that euscaphic acid G treatment inhibited IKKα/β phosphorylation and IκBα phosphorylation, which subsequently caused the blockage of NF-κB p65 phosphorylation and nuclear translocation.

Conclusion: In conclusion, these results suggested that euscaphic acid G from G. longituba showed potential anticancer effects against lung cancer cells via inducing cell cycle arrest and apoptosis, at least partly, through NF-κB signaling pathways.

Keywords: Anticancer; Glechoma longituba; Hexacyclic triterpene acid; Lung cancer; Nuclear factor-κB.