Isolation and characterization of the chemical constituents from Gynura bicolor and G. divaricata

Two Gynura species, G. bicolor and G. divaricata, are used in folk recipes for the treatment of diabetes mellitus in south China. Our previous pharmacological study proved that both plants showed significant hypoglycemic activity on normal and alloxan-diabetic mice. Sixteen chemical constituents were isolated from the CH₂Cl₂ and EtOAc extracts of the aerial parts of G. bicolor. Their structures were determined spectroscopically as hydroxymethylfurfural, benzoic acid, 4-hydroxybenzoic acid, protocatechuic acid, vanillic acid, 4-hydroxybenzaldehyde, kaempferol, 3,3'-di-O-methylellagic acid-4-O-β-D-xylopyranoside, loliolide, ficusic acid, vomifoliol, dehydrovomifoliol, boscialin, (6S,9S)-roseoside, benzyl-β-D-glucopyranoside, and 2-phenylethyl-β-D-glucopyranoside. Fractionation and isolation of the EtOAc extract of aerial parts of G. divaricata yielded six compounds [succinic acid, ethyl methyl succinate, salicylic acid, isovanillic acid, 4-hydroxycinnamic acid, esculetin]. All compounds, except 4-hydroxybenzoic acid and kaempferol, were isolated for the first time from these two plant sources.