Isolation and identification of phenolic compounds from Gynura divaricata leaves

Phenolic constituents were the principle bioactivity compounds exist in Gynura divaricata, little phenolic compounds were reported from the plant previously.

60% ethanol extract from the leaves of Gynura divaricata were isolated and purified by column chromatography of Silica gel, ODS and Sephadex LH-20, the structures of the isolated compounds were identified by UV, 1H-NMR, 13C-NMR and MS spectroscopic techniques. Additionally, a high-performance liquid chromatography-diode array detector-electrospray ionization-mass (HPLC-DAD-ESI-MS) analytical method was developed to identify some minor constituents in the n-butanol fraction of the ethanol extract of Gynura divaricata.

Six flavonols and one Dicaffeoylquinic acid were isolated from the leaves of Gynura divaricata, and these compounds were identified as follows: quercetin (1), kaempferol (2), kaempferol-3-O-β-D-glucopyranoside (3), quercetin-3-O-rutinoside (4), kaempferol-3,7-di-O-β-D-glucopyranoside (5), kaempferol-3-O-rutinoside-7-O-β-D-glucopyranoside (6), and 3,5-dicaffeoylquinic acid (7). A total of 13 compounds, including 9 flavonol glycosides and 4 phenolic acids, were tentatively identified by comparing their retention time (RT), UV, and MS spectrum values with those that had been identified and the published data.

This was the first time to use the HPLC-DAD-ESI-MS method to identify the phytochemicals of the genera Gynura. Moreover, compounds (6) and (7) have been isolated for the first time from the genus Gynura.