Growth inhibitory potential of quinone-rich fraction of Plumbago zeylanica L. Against MG-63 osteosarcoma cells via Bax/Bcl-2 modulation

The objectives of this study were to explore the cytotoxic potential of different fractions (Hexane, chloroform, ethyl acetate and methanol) of Plumbago zeylanica L. root powder. In this study, PzMH, PzMC, PzME, and PzMM fractions from the root powder of P. zeylanica were obtained through the cold maceration technique. The cytotoxic properties of these fractions on MG-63 cells were assessed using the MTT assay. The most potent fraction was further analyzed to understand its cytotoxic mechanism. To explore its apoptosis-inducing potential, microscopic and flow cytometric studies were conducted. Additionally, western blot analysis was used to examine the expression levels of proteins associated with apoptotic pathways. PzMH showed the highest cytotoxicity against MG-63 osteosarcoma cells, with a GI50 value of 53.07 µg/ml. Flow cytometric studies revealed an upsurge in reactive oxygen species and disruption of mitochondrial membrane potential. The highest concentration of PzMH fraction (183.48 µg/ml) led to 62 % cell population arrest at G0/G1 stage. The anti-apoptotic protein Bcl2 was downregulated, with p53, cleaved-caspase 9, cleaved-caspase3, Bad and Bax expression upregulated. HPLC analysis revealed the presence of lawsone, p-coumaric acid, plumbagin, and 4-hydroxy benzaldehyde, indicating that the quinone-rich fraction of Plumbago zeylanica L. attenuates the proliferation of MG-63 osteosarcoma cells through the Bax/Bcl-2 pathway. To the best of our current knowledge, this marks the first documented case where the hexane fraction enriched with quinones extracted from the roots of P. zeylanica demonstrates its ability to induce apoptosis by influencing the Bax/Bcl2 pathway.