Discovery and structural optimization of 9-O-phenylsulfonyl-berberines as new lipid-lowering agents

Abstract

Berberine is a quaternary isoquinoline alkaloid that exhibits potent hypoglycemic and hypolipidemic activity. Many medicinal chemists are currently working on structural modifications around the parent scaffold of berberine, expecting to further enhance its hypolipidemic activity and reducing its cytotoxicity. In this study, a focused berberine-like compound library containing 12,600 molecules was built via the introduction of various "drug-like" fragments at the C8 and C9 positions of berberine. Sixteen comopounds were hit by using the in-house QSAR models previously reported by our group. Considering synthesis feasibility and the cost of building-blocks, only four berberine analogs (library ID: 2028, 3847, 6033, and 12456) were selected and synthesized for investigating their lipid-lowering activities. Preliminary lipid-lowering study showed that compound 12456 with the phenylsulfonyl group at the C9 position had potent cholesterol inhibitory activity in HepG2 cells, superior to that of the parent compound berberine. Subsequently, a total of twenty-five 9-O-phenylsulfonyl-berberines (1a-1y) and twenty-four 9-O-phenylsulfonyl-tetrahydroberberine (2a-2x) were designed, synthesized, and evaluated by lipid-lowering experiments. The results displayed that most compounds exhibited more lipid-lowering activities than berberine. Among them, compound 1m inhibited cholesterol production close to 50% in both cell models when compared with the blank control; the inhibition of triglycerides exceeded 70%. Moreover, 1m also had significant pharmacological effects on the inhibition of LDLC and promotion of HDLC production, especially in the HepG2 cell model, in which the inhibitory rate against LDLC was close to 70% and the increase rate of HDLC was more than 75%. The hypolipidemic experiment of SD rats demonstrated that after 40 days of administration (1m, 15 mg/kg/d), blood cholesterol was reduced by 19.6%, triglycerides reduced by 34.52%, and LDLC reduced by 41.49%, when compared with the high-fat diet model (HFD). In addition, after 80 days of administration, the three indexes of 1m were still better than that of berberine. Oil Red O staining and H&E staining results showed that 1m exhibited potent lipid scavenging activity. All in all, 1m was discovered and identified as a potent lipid-lowering agent and a new berberine-like candidate, being evaluated by subsequent studies.

Keywords: Berberine; High-density lipoprotein cholesterol; Hypolipidemic activity; Low-density lipoprotein cholesterol; Total cholesterol; Triglyceride.