Preparative isolation, quantification and antioxidant activity of dihydrochalcones from Sweet Tea (Lithocarpus polystachyus Rehd.)

• High purity of three dihydrochalcones was successfully obtained by HSCCC.
• Evaluation of dihydrochalcones antioxidant activity was determined by the DPPH assay.
• Quantitative analysis of the isolated dihydrochalcones was performed by HPLC method.
• The HPLC analytical method has good precision, accuracy and repeatability.

Dihydrochalcones are the main active components of Lithocarpus polystachyus Rehd. (Sweet Tea), they are directly related to the sweet tonic beverage and traditional herb. In this work, two runs of preparative high-speed counter-current chromatography (HSCCC) with a two-phase solvent system composed of n-hexane/ethyl acetate/ethanol/water (1:4:3:4, v/v) were employed to separate three dihydrochalcones (phloridzin, trilobatin and phloretin) from Sweet Tea. About 6.4 mg of phloridzin, 48.4 mg of trilobatin, and 4.7 mg of phloretin with purities of 96.7%, 98.4% and 98.1% were obtained from 130 mg of the crude Sweet Tea extract. Phloridzin, trilobatin, and phloretin had effective radical scavenging activities, with IC50 values of 866.80, 20.16 and 179.47 μg/mL, respectively, in a 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical method. The contents of phloridzin, trilobatin and phloretin in dried old leaves and tender leaves of tea were in the range of 10.1–18.0, 113.7–128.8, 3.6–4.3 mg/g and 9.3–9.8, 82.9–103.1, 1.9–2.5 mg/g, respectively. The results indicated that the HPLC had good precision, accuracy and repeatability for the determination of three dihydrochalcones in samples.