Abstract

EXPLORING ANTI-HYPERGLYCEMIC POTENTIAL OF ALKALOID COMPOUNDS FROM CATHARANTHUS ROSEUS G. DON (L) AGAINST VARIOUS TYPE II DIABETES TARGETS BY IN SILICO VIRTUAL SCREENING

Thanh-Hoang Nguyen-Vo, Dat Nguyen, Phuc H. Le and Ly Le*

ABSTRACT

Background: Catharanthus roseus (L.) G. Don (C. roseus) is a prominent anticancer herb having high alkaloid content. Besides known anticancer effect, this plant has been also traditionally used as an effective anti-diabetic treatment in many Asian countries, such as India, Malaysia, and Vietnam. Some in vivo and in vitro studies on its compounds and fractional extracts have confirmed its strong anti-hyperglycemia. This fact raises a question whether alkaloid compounds probably play any function in inhibitory activity on proteins related to Type 2 Diabetes Mellitus (T2DM). This study, therefore, was conducted not only to assess the role of alkaloid compounds in glucoregulatory pathway but also investigate other chemical groups treating T2DM besides known ones such as polyphenols and terpenoids. Objective: The study aims to calculate the binding affinity of alkaloids compounds of C. roseus toward four target proteins including 11β-HSD1, PTP1B, α-glucosidase and DPPIV for anti-hyperglycemic effect and investigate their molecular interaction modes inside the protein’s active sites. Besides, pharmacokinetics of these compounds were also evaluate to support the conclusion of potent drug candidates for T2DM treatment. Method: Molecular Dynamics (MD) simulation was processed on pre-docking protein to assess the their stability. Then, the structure-based virtual screening was processed to evaluate the binding free energy of the alkaloid compounds when they were in contact with the protein active sites. Potent compounds whose binding free energy was greater than or equal to those of the control ligands were selected for pharmacophore analysis to investigate which functional residue got involve in the interaction. Besides, pharmacokinetics evaluation was done to assess the adverse drug interaction. All the in silico results were combined to explain and suggest potent compounds. Results: All structure of protein was simulated to assess the stability before processing structure-based virtual screening. After structure-based screening, 12 potential compounds were sellected. Then, pharmacokinetics of all compounds was evaluated. Enzyme CYP2C9 is considered to be the least targeted isoform while CYP2D6 is the most targeted one, followed by CYPA4. Structure-based pharmacophore features of these compounds were also analyzed to understand their molecular interaction modes and explain the differences in binding free energy. Conclusion: After combining all the in silico result, there were 8 compounds (com_05, com_07, com_16, com_26, com_27, com_28, com_46, and com_56) were suggested to be potent drug candidates for experimental confirmation. Besides, com_56 (Strictosidine lactam) and com_46 (Mitraphyllline) are considered to be two best top-hit ligands with extremely high docked score. These ligands, however, well targeted on 11-β-HSD1. Moreover, since 4 in 8 compounds well targeted on 11-β-HSD1, this protein is undoubtly confirmed as the most suitable receptor for in vitro testing. On the other hand, although com_21 (Alstonine) was temporarily rejected due to targeting on up to 3 three CYP enzyme, the potential role of this compound should be carefully re-assess because it is the only multi-target compounds toward to 4 proteins.

Keywords: C. roseus; alkaloid; structure-based virtual screening; pharmacophore; pharmacokinetics.