Separation of polar antioxidants from Rhizoma Polygonatum Odorati by high-speed counter-current chromatography with a hydrophilic solvent system

ABSTRACT

Some highly polar compounds are quality control makers for medicinal herbs. However, investigation of them has been hampered because the existing fractionation steps are difficult and laborious to purify them. Similar situations happen to Rhizoma Polygonatum Odorati, a widely used food supplement and medicinal herb with strong antioxidant activity, and up to date, only ethyl acetate fraction of Rhizoma Polygonatum Odorati has been comprehensively investigated. Here, HSCCC using a hydrophilic solvent system composed of n-butanol–ethanol–2 M ammonium sulfate (1:1:2, v/v/v) was performed to isolate highly polar antioxidants in n–butanol fraction of Rhizoma Polygonatum Odorati, guided by DPPH–HPLC experiment. Afterward, Sephadex LH-20 column chromatography eluted by methanol was selected to eliminate ammonium sulfate and purify co-eluted compounds in HSCCC collected fractions. Finally, nine compounds, including four nucleosides, cytidine (1), uridine (4), guanosine (5), and adenosine (8); two nucleobases, guanine (3), and adenine (6); and three amino acids, tyrosine (2), phenylalanine (7), and tryptophan (9) with purities over 98% were achieved and identified by UV, MS, and ¹H NMR data. Notably, compounds 1–9 were first reported in genus Polygonatum. The results indicated that the proposed method was an efficient approach to isolate and purify highly polar compounds from complex extracts.

GRAPHICAL ABSTRACT

KEYWORDS:

• Amino acid
• HSCCC
• nucleobase
• nucleoside
• preparative solution
• Rhizoma Polygonatum Odorati