Decreased S Phase and G2/M Phase Cells by a Bioactive Fraction from the Hexane Extract of Rhododendron aroboreum Leading to the Apoptosis of HeLa Cells In-Vitro

Abstract

Search for novel anticancer compounds from natural sources is a priority goal of cancer biologists. Rhododendron arboreum is one of the most stately and impressive Rhododendron species. In hilly areas, the flowers of R. arboreum are used for the treatment of chronic diseases. The current study was aimed to evaluate the anti-proliferative property of R. arboreum on HeLa cells. Crude extract of the flower was prepared using serial extraction procedure with different solvents. Cytotoxicity of the extracts on HeLa, CHO and human lymphocytes were assessed using MTT assay and trypan blue dye exclusion methods. The extract was further purified by TLC and characterized by LC-MS method. The hexane extract showed significant cytotoxicity to HeLa cells. This extract was fractionated using thin layer chromatography, 6 fractions were isolated, out of which fraction 3 showed the maximum cytotoxic activity with an IC50 of 15 μg/mL. The mechanism of action was observed as apoptosis induction as indicated by elevated caspase activity and inhibition of cell cycle with reduced cell population in the S and G2/M phases. LC-MS analysis of this promising bioactive fraction resulted in a molecular ion fragment with an m/z value of 437.48 which is corresponding to that of brefeldin A, an anticancer compound. It can be concluded that R. arboreum flower has cytotoxic activity which could be due to the presence of brefeldin A, that warrants further studies on purification and characterization towards the development of highly efficient therapeutics for cancer.
 HIGHLIGHTS
 
 Anti-cancer drug discovery from natural sources like medicinal herbs having diverse metabolites of therapeutic significance provide lead molecules towards cancer drug development
 The anti-proliferative/apoptotic potential of a bioactive fraction from Rhododendron aroboreum, was analysed on cancer cell lines by MTT, Lactate dehydrogenase, Caspase and cell cycle studies. The bioactive compound was characterized through preparative TLC and LC-MS methods
 The potent apoptotic potential of Rhododendron aroboreum flower extract was demonstrated through reduced S-phase and G2/M phase cells, increased caspase, LDH activities in our study results
 The presence of Brefeldin A, previously reported as an anticancer compound in a microbe, was observed for the 1st time in Rhododendron aroboreum through our study in LC-MS analysis
 
 GRAPHICAL ABSTRACT