Hirtionosides A-C, gallates of megastigmane glucosides, 3-hydroxyoctanoic acid glucosides and a phenylpropanoid glucoside from the whole plants of Euphorbia hirta

From the 1-BuOH-soluble fraction of a MeOH extract of Euphorbia hirta, collected in the Okinawa islands, three new megastigmane glucoside gallates, named hirtionosides A-C, 3-hydroxyoctanoic acid glucosides and a phenylpropanoid glucoside were isolated along with 15 known compounds. The structures of the new compounds were elucidated by detailed analysis of physical data, including one- and two-dimensional NMR spectra, and those of known compounds were determined by comparison of physico-chemical data with those reported in the literature. The absolute structures of the megastigmanes were determined by comparison of NMR data and Cotton effects in the CD spectra. The modified Mosher's method was applied to determine the absolute structure of the chiral center in 3-hydroxyoctanoic acid. The DPPH radical-scavenging properties of megastigmane glucoside gallates were assayed and, as expected, they showed moderate activity.