Epiberberine, a natural protoberberine alkaloid, inhibits urease of Helicobacter pylori and jack bean: Susceptibility and mechanism

In our previous study, Rhizoma Coptidis extract was found to exert more potent inhibitory effect than its major component berberine towards urease from Helicobacter pylori (HPU) and jack bean (JBU). In continuation of our work, the present study was designed to further comparatively investigate the urease inhibitory activities of five major protoberberine alkaloids in Rhizoma Coptidis, namely berberine, palmatine, coptisine, epiberberine, jateorhizine to identify the bioactive constituent, and illuminate the potential mechanism of action. Results indicated that the five protoberberine alkaloids acted as concentration-dependent inactivators of urease with IC₅₀ values ranging between 3.0 and 5087μM for HPU and 2.3->10,000μM for JBU, respectively. Notably, epiberberine (EB) was found to be the most potent inhibitor against both ureases with IC₅₀ values of 3.0±0.01μM for HPU and 2.3±0.01μM for JBU, which was more effective than the standard urease inhibitor, acetohydroxamic acid (83±0.01μM for HPU and 22±0.01μM for JBU, respectively). Further kinetic analysis revealed that the type of EB inhibition against HPU was slow-binding and uncompetitive, with K_i of 10.6±0.01μM, while slow-binding and competitive against JBU with K_i of 4.6±0.01μM. Addition of thiol reagents, such as l-cysteine, glutathione and dithiothreitol, significantly abolished the inhibition, while Ni²⁺ competitive inhibitors, boric acid and sodium fluoride, synergetically inhibited urease with EB, indicating the obligatory role of the active site sulfhydryl group for the inhibition. In addition, binding of EB with the urease proved to be reversible, as about 65% and 90% enzymatic activity of HPU and JBU, respectively, could be restored by dithiothreitol application. These findings highlighted the potential role of Rhizoma Coptidis protoberberine alkaloids, especially EB, as a lead urease inhibitor in the treatment of diseases associated with ureolytic bacteria. Thus, EB had good potential for further development into a promising therapeutic approach for the treatment of urease-related diseases.

Induced cortical neurogenesis after focal cerebral ischemia--Three active components from Huang-Lian-Jie-Du Decoction

ETHNOPHARMACOLOGICAL RELEVANCE

Huang-Lian-Jie-Du-Decoction (HLJDD) is a Traditional Chinese Medicine (TCM) clinical prescription noted for its neuroprotective effects. The total alkaloids, flavonoids, and iridoids are the main active components of HLJDD. In the present study we explored the possible effects of the total alkaloids, flavonoids, and iridoids from HLJDD on behavioral recovery and cortical neurogenesis after stroke.

METHODS

The stroke model was induced by permanent middle cerebral artery occlusion (pMACO). The total alkaloids (44 mg/kg), flavonoids (50 mg/kg), and iridoids (80 mg/kg) from HLJDD were orally administered for 2h after stroke and daily thereafter. Neurological function was assessed and then rats were sacrificed 7 days after pMACO. Following repeated intraperitoneal injections of the cell proliferation - specific marker 5-bromodeoxyuridine (BrdU) after stroke induction, precursor cell proliferation and differentiation was monitored by immunofluorescent staining. The levels of relevant proteins were determined by western blotting and the mRNA expressions were assessed by quantitative real time-polymerase chain reaction (qRT-PCR).

RESULTS

Total alkaloids, flavonoids and iridoids from HLJDD showed improved functional outcome after brain ischemia. The total alkaloids and iridoids increased number of BrdU-positive cells and enhanced neuronal differentiation in the cortex. Alkaloids-enhanced neurogenesis might be associated with increased VEGF, Ang-1, and Ang-2 protein expression. And the neuroproliferative effect of alkaloids was partially correlated with increased phosphorylation of AKT, and GSK-3β. Flavonoids treatment was found to promote differentiation of cortical precursor cells into neuronal but not glial cells, which may be at least attributable to the regulation of AKT, GSK-3β mRNA and Ang-1 protein levels.

CONCLUSIONS

Total alkaloids, iridoids and flavonoids from HLJDD promoted functional recovery likely via enhancing cortical neurogenesis and thus have potential as a treatment for ischemic brain injury.

Epiberberine reduces serum cholesterol in diet-induced dyslipidemia Syrian golden hamsters via network pathways involving cholesterol metabolism

This study aimed to evaluate the cholesterol-lowering effect of epiberberine in dyslipidemia Syrian golden hamsters induced by high fat and high cholesterol (HFHC) diet and its regulation mechanism on some key genes involved in cholesterol metabolism. Hamsters were divided into six groups: normal control group (NC), HFHC group, simvastatin (Sim) and three doses of epiberberine group. The body weight, organs weight and serum lipid levels, as well as total cholesterol (TC) and total bile acids (TBA) levels in liver and feces were determined. Furthermore, the antidyslipidemia effect of epiberberine on key genes involved in cholesterol biosynthesis, uptake, conversion and elimination such as 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR), low density lipoprotein receptor (LDL receptor), 7-alpha-hydroxylase (CYP7A1) and apical sodium dependent bile acid transporter (ASBT) were investigated. The results showed that epiberberine at high dosage significantly reduced serum TC, low density lipoprotein cholesterol (LDL-c) and TBA levels by 20.2%, 22.3% and 43.8%, respectively, and increased TBA and TC levels in feces. Epiberberine inhibited HMGCR mRNA and protein expressions and slightly reduced the protein level of ASBT, as well as dramatically up-regulated mRNA and protein expressions of CYP7A1 and LDL receptor. These findings suggested that the antidyslipidemia effects of epiberberine can be achieved via inhibiting the synthesis of cholesterol, promoting the uptake and conversion of TC in liver and increasing the excretion of TC and TBA in feces. Thus, epiberberine should be considered as one of the promising natural drugs for the treatment of dyslipidemia.