Analytical evaluation of steviol glycosides by capillary electrophoresis supported with molecular docking studies
This paper reports on a newly developed electrokinetic chromatographic method for the simultaneous separation and determination of steviol glycosides in real stevia samples by capillary electrophoresis and supported by molecular docking studies. Our results obtained using 30-mM heptakis-(2,3,6-tri-o-methyl betacyclodextrin) as a separating agent, suggest that at optimum experimental conditions the detection limits of 2.017 × 10−5 and 7.386 × 10−5 M and relative standard deviations (n = 5) of 1.10 and 1.17 were obtained for rebaudioside-A and stevioside, respectively. In addition, the molecular docking studies explained to a certain extent why the separation was successful. The calculated binding free energy results for the rebaudioside-A and stevioside complexes formed with the separating agent showed that although both ligands penetrated deeply into the hydrophobic cavity of the separating agent, the presence of additional hydrogen bonding in the case of stevioside is probably responsible for its stronger binding affinity than that of rebaudioside-A.
KeywordsSteviol glycosides (rebaudioside-A, stevioside) Heptakis 2,3,6-tri-o-methyl betacyclodextrin (TM-β-CD) Capillary electrophoresis (CE) Molecular docking (MD)
KB is grateful for the financial support provided by the Durban University of Technology and National Research Foundation of South Africa for this work. The authors would like to express their acknowledgement to the Centre for High Performance Computing, an initiative supported by the Department of Science and Technology of South Africa.
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