Experimental and quantum-chemical study of nucleophilic substitution mechanism in berberine

9-N-n-alkyl Berberine Derivatives: Hypoglycemic Activity Evaluation

Several novel 9-N-n-alkyl derivatives of berberine (C5, C7, C10, C12) were synthesized. They were analyzed in vitro and in vivo for their hypoglycemic activity. In vitro studies showed that the derivatives with shorter alkyl substitutes at concentrations ranging from 2.5 to 10 μM were able to stimulate glucose consumption by HepG2 cells more prominently than the derivatives with longer substitutes (C10 and C12). All compounds demonstrated a better effect compared to berberine. Their impact on cells' viability also depended on the alkyl substitutes length, but in this case, C10 and C12 derivatives demonstrated the best results. A similar correlation was also found in the OGTT, where the C5 derivative demonstrated a pronounced hypoglycemic effect at a dose of 15 mg/kg and C12 was less effective. This compound was further investigated in C57BL/6^Ay mice for four weeks and was administered at a dose of 15 mg/kg. Pronounced effect of C12 on carbohydrate metabolism in mice was discovered: there was a decrease in fasting glucose levels and an increase in glucose tolerance in OGTT on the 14th and 28th days of the experiment. However, at the end of the experiment, signs of hepatosis exacerbation and an increase in the content of hepatic aminotransferases in blood were found.

Discovery of the First in Class 9-N-Berberine Derivative as Hypoglycemic Agent with Extra-Strong Action

Berberine is well known for its ability to reduce the blood glucose level, but its high effective dose and poor bioavailability limits its use. In this work we synthesized a new derivative of berberine, 9-(hexylamino)-2,3-methylenedioxy-10-methoxyprotoberberine chloride (SHE-196), and analyzed the profile of its hypoglycemic effects. Biological tests have shown that the substance has a very pronounced hypoglycemic activity due to increased insulin sensitivity after single and multiple dosing. In obese type 2 diabetes mellitus (T2DM) mice, it was characterized by improved glucose tolerance, decreased fasting insulin levels and sensitivity, decreased total body weight and interscapular fat mass, and increased interscapular brown fat activity. All these effects were also confirmed histologically, where a decrease in fatty degeneration of the liver, an improvement in the condition of the islets of Langerhans and a decrease in the size of fat droplets in brown adipose tissue were found. Our results indicate that 9-(hexylamino)-2,3-methylenedioxy-10-methoxyprotoberberine chloride could be the first in a new series of therapeutic agents for the treatment of diabetes mellitus.

Neutral Pyrrole Nitrogen Atom as a π- and Mixed n,π-Donor in Hydrogen Bonding

9-Dimethylaminobenzo[ g]indoles 3-6 and 1-dimethylamino-8-(pyrrolyl-1)naphthalene 7 were examined as possible models for establishing the ability of the pyrrole nitrogen atom to participate in [NHN]⁺ hydrogen bonding as a proton acceptor. Indoles 3-5 (to a lesser extent 6) form rather stable tetrafluoroborates, with the proton mostly located on the NMe₂ group but simultaneously engaged in the formation of a charged intramolecular [NHN]⁺ hydrogen bond (IHB) with the pyrrole N atom. The theoretically estimated energies of IHB in salts 3H⁺BF₄^--6H⁺BF₄^- vary between 7.0-10.7 and 6.2-7.0 kcal mol^-1 in vapor and MeCN, respectively. The pyrrole N atom undergoes a perceptible pyramidalization but still remains involved in the 6π-electron aromatic system, suggesting that the hydrogen bonding in salts 3H⁺BF₄^--6H⁺BF₄^- represents a previously unknown mixed NH···N(n,π) interaction. Despite the favorable orientation of the N-H bond and the pyrrole ring in salt 7H⁺BF₄^-, no signs of NH···N(n) bonding in it were noticed, and the existing interaction was classified as pure NH···N(π). The results obtained may be useful in studies of secondary protein structures, especially those α-helix sections which contain tryptophan residues.