RESUMO
ETHNOPHARMACOLOGICAL RELEVANCE: Markhamia tomentosa (Benth) K. Schum ex. Engl. (Bignoniaceae), a tree widely dispersed in West Tropical Africa, is used traditionally to treat various diseases as it possesses antimicrobial, antioxidant, analgesic, anticancer and anti-inflammatory activities. MATERIALS AND METHODS: This study evaluates the cytotoxic effect and underlying mechanisms of the ethanolic extract of Markhamia tomentosa on HeLa and MCF-7 cancer cell lines and non-cancerous Vero cell line. Brine shrimp lethality test was used for preliminary screening. Cytotoxicity was determined using the MTT assay and IC50 was calculated. Effect of Markhamia tomentosa on the cell cycle was monitored by flow cytometry and the apoptosis-induction capability confirmed by exposure of phosphatidylserine to the outer leaflet of the plasma membrane. Loss of mitochondrial membrane potential was analysed by flow cytometry using JC-1. RESULTS: Markhamia tomentosa was toxic to brine shrimps with LD50 of 31.62µg/ml. Cell viability and growth of HeLa cells was inhibited by the extract with an IC50 of 189.1±1.76µg/ml at 24h post treatment. However, no cytotoxic effect was observed in MCF-7 and Vero cell lines. The extract induced cell cycle arrest in HeLa cells in the G0/G1 phase resulting in cell death after 24h exposure. Induction of apoptosis in HeLa cells was substantiated by Annexin V-FITC/PI double staining showing phosphatidylserine translocation and depolarisation of the mitochondrial membrane potential by flow cytometry of JC-1 stained cells. CONCLUSION: The ethanolic extract of Markhamia tomentosa induces G0/G1 in HeLa cells followed by induction of the intrinsic pathway of apoptosis.