Iridoid glycosides link with phenylpropanoids from <i>Rehmannia glutinosa</i>

Abstract

Two new iridoid glycosides link with phenylpropanoids, rehmanniosides G (<b>1</b>) and H (<b>2</b>) along with 11 known compounds, 6-O-(<i>E</i>)-caffeoylajugol (<b>3</b>), 6-<i>O</i>-(<i>E)</i>-feruloylajugol (<b>4</b>), verbasoside (<b>5</b>), jionoside C (<b>6</b>), acteoside (<b>7</b>), leucosceptoside A (<b>8</b>), brachynoside (<b>9</b>), jionoside B1 (<b>10</b>), jionoside A1 (<b>11</b>), isoacteoside (<b>12</b>) and isomartynoside (<b>13</b>) were isolated from the roots of <i>Rehmannia glutinosa</i> (Gaertn.) DC. Their chemical structures were elucidated on the basis of extensive spectroscopic methods, including 1D, 2D NMR and mass spectra. Compounds <b>7 - 11</b> showed significant inhibitory <i>α</i>-glucosidase with IC₅₀ values ranging from 261.4 to 408.7 μM (acarbose, IC₅₀ of 204.2 ± 19.9 μM).[Formula: see text].