Phytochemical analysis : PCA · 2020
Isothermal kinetics of ethanolic extraction of total hypericin from pre-extracted Hypericum perforatum flowers.
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Adnadjevic Borivoj, Koturevic Biljana, Jovanovic Jelena
Аннотация
INTRODUCTION: Hypericum perforatum L., Hypericaceae (St John's wort) is a highly familiar plant in the medicinal community which recently showed good antiviral activities including against some types of coronavirus.
OBJECTIVE: Establishing the kinetics of isothermal extraction of total hypericin (TH) from the pre-extracted flowers of H. perforatum flowers.
METHODS: The solvent extraction of TH from the remaining solid residue after the pre-extraction procedure was performed providing isothermal conditions at the temperature of 313 K, 323 K, and 328 K (±1 K) using ethanol as a solvent. The feasibility of mathematical modelling of the isothermal kinetics of TH extraction was explored applying some of the frequently used kinetic models of solvent extraction: first-order reaction model, film theory model, unsteady-state diffusion model, parabolic diffusion model, Elovich's equation. The kinetic complexity was examined using the differential isoconversional method.
RESULTS: The kinetics of isothermal solvent extraction of TH is a kinetic elementary process with the unique rate-determining step. It was found that the kinetics of isothermal extraction of TH can be best described employing the theoretical Jander three-dimensional (3D) diffusional model and its suitability for modelling the investigated extraction was confirmed with statistical parameters [adjusted linear correlation coefficient (R2 adj ) = 0.998-0.999 and the standard error (SE) = 0.005-0.006]. The values of the model kinetic parameters (rate constant (kM /min-1 ), activation energy (Ea = 21.0 ± 4.9 kJ/mol) and pre-exponential factor (lnA = 3.1 ± 2.2 min-1 ) were calculated.
CONCLUSIONS: Based on the model mechanism of the kinetics of the investigated extraction a new mathematical model is suggested and the controlling step of the overall process was found.
OBJECTIVE: Establishing the kinetics of isothermal extraction of total hypericin (TH) from the pre-extracted flowers of H. perforatum flowers.
METHODS: The solvent extraction of TH from the remaining solid residue after the pre-extraction procedure was performed providing isothermal conditions at the temperature of 313 K, 323 K, and 328 K (±1 K) using ethanol as a solvent. The feasibility of mathematical modelling of the isothermal kinetics of TH extraction was explored applying some of the frequently used kinetic models of solvent extraction: first-order reaction model, film theory model, unsteady-state diffusion model, parabolic diffusion model, Elovich's equation. The kinetic complexity was examined using the differential isoconversional method.
RESULTS: The kinetics of isothermal solvent extraction of TH is a kinetic elementary process with the unique rate-determining step. It was found that the kinetics of isothermal extraction of TH can be best described employing the theoretical Jander three-dimensional (3D) diffusional model and its suitability for modelling the investigated extraction was confirmed with statistical parameters [adjusted linear correlation coefficient (R2 adj ) = 0.998-0.999 and the standard error (SE) = 0.005-0.006]. The values of the model kinetic parameters (rate constant (kM /min-1 ), activation energy (Ea = 21.0 ± 4.9 kJ/mol) and pre-exponential factor (lnA = 3.1 ± 2.2 min-1 ) were calculated.
CONCLUSIONS: Based on the model mechanism of the kinetics of the investigated extraction a new mathematical model is suggested and the controlling step of the overall process was found.