Preparative isolation of four new and two known flavonoids from the leaf of Patrinia villosa Juss. by counter-current chromatography and evaluation of their anticancer activities in vitro

A preparative counter-current chromatography (CCC) was used to isolate and separate chemical constituents from the leaf of Patrinia villosa, a famous traditional Chinese medicinal herb. Six flavonoids including two known and four novel compounds were successfully simultaneous purified by CCC with a two-phase solvent system composed of n-hexane–ethyl acetate–methanol–water (10: 13: 13: 10, v/v) by increasing the flow rate of the mobile phase from 1.0 ml/min to 2.0 ml/min after 110 min to bring out the late eluters. The separation produced total of 44.9 mg fraction I with 99.1% purity, 35.5 mg fraction II with 98.8% purity, 79.8 mg fraction III with 99.3% purity, 45.8 mg fraction IV with 98.8% purity, 39.8 mg fraction V with 98.6% purity and 9.6 mg fraction VI with 97.5% purity from 400 mg crude extract in one single isolation procedure and less than 10 h, and the obtained fractions were all analyzed by high performance liquid chromatography (HPLC). Their chemical structures were elucidated as (2S)-5,7,2′,6′-tetrahydroxy-6,8-di (γ,γ-dimethylallyl) flavanone (1), (2S)-5,7,2′,6′-tetrahydroxy-6-lavandulylated flavanone (2), (2S)-5,7,2′,6′-tetrahydroxy-4′-lavandulylated flavanone (3), (2S)-5,2′,6′-trihydroxy-2″,2″-dimethylpyrano [5″, 6″: 6, 7] flavanone (4), (2S, 3″S)-5,2′,6′-trihydroxy-3″-γ,γ-dimethylallyl-2″,2″-dimethyl-3″,4″-dihydropyrano [5″, 6″: 6, 7] flavanone (5) and licoagrochalcone B (6), respectively, by spectrum methods including UV, IR, high resolution (HR)-electrospray ionization (ESI)-MS, 1-dimension (1D) and 2-dimension (2D) NMR techniques. Among them, compounds 2, 3, 4, and 5 were new compounds and discovered from nature for the first time. The recoveries of the six compounds were 91.2%, 91.4%, 92.1%, 90.5%, 90.3% and 89.7%, respectively, in CCC step. Subsequently, their anticancer activities were also examined to inhibit human cancer cells’ growth including A549, BEL-7402, SGC-7901, MCF-7, HT-29, K562 and A498 cell lines by MTT method in vitro. The results indicated that the compounds 1, 2 and 3 exhibited high anticancer activities (IC50 < 7 μg/ml), especially to K562 cancer cell (IC50 < 3.1 μg/ml), and the compounds 4, 5 and 6 exhibited weaker inhibition effect (IC50 < 30 μg/ml).