Unequivocal glycyrrhizin isomer determination and comparative in vitro bioactivities of root extracts in four Glycyrrhiza species

Farag, Mohamed A.; Porzel, Andrea; Wessjohann, Ludger A.

A spectrophotometric method using Folin-Ciocalteau reagent was adapted for TP assays in Glycyrrhiza roots. Extracts were prepared by cold extraction with shaking over 3 h using 100% MeOH. Plant debris was removed by centrifugation and solvent was removed by evaporation under nitrogen followed by lyophilization. The residue was dissolved in methanol to obtain a solution at a concentration of 10 mg/ml. Folin Ciocalteau reagent (100 ll) was added to a test tube containing 20 ll of extract. Contents were mixed and a saturated sodium carbonate solution (200 ll) was added to the tube. The volume was adjusted to 1 ml by the addition of 0.68 ml of milliQ water and contents were mixed vigorously. Tubes were allowed to stand at room temperature for 25 min and then centrifuged for 5 min at 2435g. Absorbance of the supernatant was read at 760 nm. Blank samples of each extract or fraction were used for background subtraction. Caffeic acid was used as standard for the calibration curve at concentrations of 0.01, 0.1, 1, and 5 mg/ml. The assay was carried out in triplicate.