Anti-leukemic effect of fractions derived from the ethanolic extract of Elsholtzia stachyodes and its active components

Abstract

Northern Indochina is a region with abundant and diverse natural resources, including ethnomedicinal plants that have been traditionally used to alleviate cancer-like symptoms. However, the literature reviews regarding the scientific and clinical validation of the active ingredients and signaling mechanisms for cancer-like symptoms and therapeutic application are still lacking. We summarize and exemplify the plants used in ethnopharmacology for traditional cancer treatment based on the historical wisdom of 10 ethnic groups residing in northern Indochina. Additionally, the major natural active pharmaceutical ingredients components with anticancer mechanisms are also elucidated and discussed. 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. In this study 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. The ethanolic extracts and fractions were screened for cytotoxicity using flow cytometry. High Performance Liquid Chromatography (HPLC) and Liquid Chromatography-Mass Spectrometer (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). The results showed that 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. 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.