Cytotoxic activity of Cape Fynbos against triple-negative breast cancer cell line

Abstract

• Erica glabella, Hippia frutescens and Salvia africana-lutea ( methanol), and Eriocephalus racemosa ( hexane) extracts IC 50 at < 30 µg/mL • Eriocephalus racemosa induced 21.48±2.86% apoptosis similar to cisplatin 23.72±4.36%. • Metabolite profiling of Salvia africana-lutea extract revealed the presence of phosphatidylcholines, triterpenoids, oxepane and 7-O-methylated flavonoids derivatives. Breast cancer is a leading cause of cancer-related deaths in women globally. Even though a plethora of treatments are available, most patients experience adverse effects which affect their quality of life. The aim of this study was to investigate the utility of nine Fynbos plants ( Erica magnisylvae E.G.H Oliv., Erica canescens J.C. Wendl. , Erica coccinea L. , Erica glabella Thunb. , Erica corifolia L. , Eriocephalus racemosa L. , Hippia frutescens L., Salvia africana-lutea L. and an unknown Fynbos plant) in treating breast cancer. Solvent extraction of fynbos plants was performed, and crude extracts were evaluated against MDA-MB 231 cancer cell line to determine the cytotoxic activity with the mode of cell death confirmed using flow cytometry. Antioxidant activity and mass spectrometry-based metabolite profiling were performed to characterize and identify the phytochemical constituents of the extracts. The methanol extracts from E. glabella ., H. frutescens and S. africana-lutea and the hexane extract from E. racemosa showed promising cytotoxic activities in the screening phase and thus were further evaluated to determine their 50% inhibitory concentrations (IC 50 ) which were found to be < 30 µg/mL. Flow cytometry analysis of treated MDA-MB 231 cells revealed promising results for the hexane crude extract (leaves) of E. racemosa and stem methanol crude extract of H. frutescens which induced apoptosis in MDA-MB-231 cancer cell line, similar to the reference drug cisplatin. Metabolite profiling of S. africana-lutea extract, the most potent apoptosis inducer in this study, revealed the presence of phosphatidylcholines, triterpenoids, oxepane and 7-O-methylated flavonoids derivatives. It was concluded that E. racemosa and S. africana-lutea are excellent candidates for further development of therapeutic agents in the fight against cancer, given the pressing need for novel efficacious agents.