The anti-leukemic activity of a luteolin-apigenin enriched fraction from an edible and ethnomedicinal plant, Elsholtzia stachyodes, is exerted through an ER stress/autophagy/cell cycle arrest/ apoptotic cell death signaling axis.

Background: Elsholtzia is a genus in the family Lamiaceae, and some species in this genus are commonly used for food and in ethnomedicinal formulations by some ethnic groups of China and Thailand. Despite their apparent utility, few studies have been conducted to evaluate their potential as sources of medicinally active agents.

Purpose: We aimed to investigate the cytotoxicity of ethanolic extracts from three selected edible plant species of the genus Elsholtzia and the most promising extract was further characterized for the bioactive constituents and signaling mechanisms associated with the anti-leukemic activity.

Materials And Methods: Ethanolic extracts were screened for cytotoxicity using flow cytometry. HPLC and LC-MS were used to analyze the chemical constituents of the most potent fraction from E. stachyodes. The relevant mechanism of action was assessed by western blot and multispectral imaging flow cytometry (MIFC).

Results: The most potent anti-leukemic activity was observed with the ethanolic extract from E. stachyodes. Luteolin and apigenin were characterized as the major constituents in the fraction from E. stachyodes. Mechanistically, the luteolin-apigenin enriched fraction (LAEF) induced the UPR, increased autophagic flux, induced cell cycle arrest and apoptotic cell death. LAEF showed significantly less cytotoxicity towards peripheral blood mononuclear cells (PBMCs) as compared to leukemia cell lines.

Conclusion: This study is the first to report E. stachyodes as a new source of luteolin and apigenin which are capable of triggering leukemic cell death. This could lead to a novel strategy against leukemia using ethnomedicinal plant extracts as an alternative or supplemental anti-cancer agent.