Synthesis of a novel fluorescent berberine derivative convenient for its subcellular localization study

Berberine is a naturally occurred isoquinoline alkaloid that shows great potential for developing anticancer drugs. However, the problem stays of poor understanding of the mechanisms of anticancer action of berberine. It depends on evaluation of berberine's pharmacokinetics, namely monitoring of its uptake and distribution in cells, tissues and organs. In order to address these problems, we have designed and synthesized a novel berberine derivative BBR-BODIPY bearing a fluorescent tag that allows screening its interaction with the targeted cells. It was shown that the synthesized fluorescent derivative could penetrate into human breast carcinoma MCF7 cells, and then induced apoptosis detected by the Western Blot analysis as changed expression of apoptosis-related proteins, including Bax, Bcl2, and Cyto C released from mitochondria, Cleaved Caspase 9, Cleaved PARP, Pro-Caspase 3, and Cleaved Caspase 3. The results of MitoTracker analysis followed by the confocal microscopy of sub-cellular localization of BBR-BODIPY in the MCF7 cells demonstrated excellent cell-penetrating ability of this compound even at low concentrations, and mitochondria was the main site of its accumulation. Together with the results of Western Blot analysis, these data indicated that the mitochondria pathway might be involved in berberine-induced apoptosis.