Synthesis and evaluation of novel 12-aryl berberine analogues with hypoxia-inducible factor-1 inhibitory activity

Eighteen novel 12-aryl berberine derivatives were synthesized and evaluated for their inhibitory effects on hypoxia-inducible factor (HIF-) 1 transcription which is a potential target for the development of anticancer agents. As a result, seven 12-phenyl berberine analogues (3a–3f, 3k) showed more potent inhibitory effect on hypoxia-induced HIF-1 transcriptional activity than the parent compound berberine (1). Notably, the 12-biphenyl berberine (3e) exhibited the strongest HIF-1 suppressing activity among all the berberine analogues with an IC50 value of 0.74 μM. The introduction of a biphenyl substituent to berberine resulted in a 5.4 fold enhancement of potency over the parent berberine (1). Structure–activity relationship analysis revealed that the phenyl substituent is a preferential pharmacophore for HIF-1 inhibitory activity of 12-aryl berberine analogues over heteroaromatic ring substituents of pyridyl, thienyl and furyl. The phenyls containing hydrophobic moieties are beneficial to increase the HIF-1 suppressing effect compared to those bearing hydrophilic ones. In addition, the p-fluoro phenyl is also a favorable pharmacophore over the m- and o-fluoro phenyls. Western blot assay revealed that berberine analogues (3a–3f, 3k) exhibited a stronger suppressive effect on hypoxia-induced expression of HIF-1α protein than berberine in both T47D and MCF-7 cells. It was also found that berberine derivatives (3a–3f, 3k) possessing more potent HIF-1 inhibitory activity generally showed a greater toxic effect on MCF-7 cancer cells. These findings may guide the rational design of berberine-based HIF-1 inhibitors for the development of anticancer drugs. This is also the first report on berberine and its derivatives' inhibitory effect on HIF-1 transcriptional activity.