Three steviol glycosides, stevioside, rebaudioside A and rebaudioside C were successfully isolated and purified from the extract of leaves of Stevia rebaudiana Bertoni by high-speed counter-current chromatography (HSCCC). Based on the principle of the partition coefficient values (k) for target compounds and the separation factor (α) between targets compounds, the two-phase solvent system which contains n-hexane–n-butanol–water at an optimized volume ratio of 1.5:3.5:5 (v/v/v) was selected for the HSCCC separation and the lower phase was employed as the mobile phase in the head to tail elution mode. In a single operation, 200 mg of the crude extract yielded pure stevioside (54 mg), rebaudioside A (36 mg), and rebaudioside C (13 mg) with the purities of 98.3%, 98.5% and 97.6%, respectively. The HSCCC fractions were analyzed by high-performance liquid chromatography (HPLC) and the structures of the three steviol glycosides were identified by 1H NMR, 13C NMR and DEPT-NMR.

The adsorption feature of different kinds of polystyrene-based macroporous adsorption resins (MARs) was investigated systemically at constant temperature employing Rutin as the adsorbate. Different from traditional adsorption patterns, Langmuir and Freundlich adsorption, and the results showed interesting aspects: (1) With the increase of the volume of the initial solution, the adsorption capacity increased to the maximum, and then decreased gradually. (2) Experimental results clearly verified the opinion that the adsorption process of MARs could be divided into three stages—macropores, mesopores, and micropores—by the capillary effects occurring at the two intersections, and the adsorption feature for every stage could be described well by the fourth type of Brunauer model. (3) The model that the inductive effect transmitted to the first layer could not interpret our experimental results reasonably. Thus, the model that the inductive effect passed on to a higher layer was proposed by investigating regression of the experimental results and the conclusion that the inductive effect transmitted to the third layer was drawn.

For the first time an RP-LC method with diode-array detection has been developed for simultaneous analysis of three flavonoids [rhamnocitrin-3-O-β-d-galactopyranoside-4′-O-β-d-glucospyranoside (RGG), rhamnocitrin-3-O-β-d-galactopyranoside (RG), and 10-methoxymedicarpin (MC)] in a methanol extract of Oxytropis kansuensis Bunge whole plant. Separation was achieved on an ODS column within 18 min. The effect of mobile phase pH on separation of the three flavonoids was investigated. Compared with relative errors obtained by use of least-squares linear regression and logarithmic regression for data processing, weighted least-squares linear regression was more accurate. Response was a linear function of concentration in the ranges 0.0091–3.4, 0.013–4.9, and 0.0085–3.2 mg mL−1 for RGG, RG, and MC, respectively, with correlation coefficients >0.9997. The amounts of the three flavonoids in O. kansuensis Bunge were successfully analyzed with satisfactory repeatability and recovery.