Abstract
In this work, the n-butanol extract from leaves of Lonicera japonica Thunb. (L. japonica) was reacted with DPPH and subjected to a HPLC analysis for the guided screening antioxidants (DPPH-HPLC experiments). Then, nine antioxidants, including flavonoid glycosides and caffeoylquinic acid derivatives, were isolated and purified from leaves of L. japonica using high speed counter-current chromatography (HSCCC) and prep-HPLC. The n-butanol extract was firstly isolated by HSCCC using methyl tert-butyl ether/n-butanol/acetonitrile/water (0.5% acetic acid) (2:2:1:5, v/v), yielding five fractions F1, F2 (rhoifolin), F3 (luteoloside), F4 and F5 (collected from the column after the separation). The sub-fractions F1, F4 and F5 were successfully separated by prep-HPLC. Finally, nine compounds, including chlorogenic acid (1), lonicerin (2), rutin (3), rhoifolin (4), luteoloside (5), 3,4-O-dicaffeoylquinic acid (6), hyperoside (7), 3,5-O-dicaffeoylquinic acid (8), and 4,5-O-dicaffeoylquinic acid (9) were obtained, respectively, with the purities over 94% as determined by HPLC. The structures were identified by electrospray ionization mass spectrometry (ESI-MS), 1H- and 13C-NMR. Antioxidant activities were tested, and the isolated compounds showed strong antioxidant activities.
Highlights
Lonicera japonica Thunb., one of the most common traditional Chinese medicines, is widely used for treating various diseases, including arthritis, diabetes mellitus, fever, infections, sores and swelling.Pharmacological studies have demonstrated that their extracts have a broad spectrum of biologicalMolecules 2017, 22, 229; doi:10.3390/molecules22020229 www.mdpi.com/journal/moleculesMolecules 2017, 22, 229 activities, such as antibacterial, anti-inflammatory, antioxidant, antipyretic, antiviral, antimicrobial, and hepatoprotective effects [1,2,3,4]
Nine compounds compounds were were separated separated and and their their chemical chemical structures structures were were elucidated by electrospray ionization mass spectrometry (ESI-MS)
The DPPH-HPLC method has been used for rapid screening of the radical scavenging properties of natural products [18]
Summary
Lonicera japonica Thunb., one of the most common traditional Chinese medicines, is widely used for treating various diseases, including arthritis, diabetes mellitus, fever, infections, sores and swelling. Preparative high-performance liquid chromatography (prep-HPLC) is a powerful tool in virtue of its excellent separation efficiency. It is more expensive and typically requires in virtue of its excellent separation efficiency. HSCCC and prep-HPLC was established for the rapid purification a method combining and prep-HPLC was established forseparation the rapid and separation and of compounds leaves offrom studies, caffeoylquinic acid derivatives from purification of from compounds leaves In of previous. L. separated japonica bus were separated with HSCCC and yet prep-HPLC [16,17], yetglycosides complex were not reported in the materials. Nine compounds compounds were were separated separated and and their their chemical chemical structures structures were were elucidated by electrospray ionization mass spectrometry (ESI-MS).
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