Structure Elucidation and Absolute Configuration Determination of Nortriterpenoids from <i>Picramnia glazioviana</i>.
Gimenes L, Luna-Dulcey L, Batista JM, Dos Santos FM, Popolin CP, Cominetti MR, Fernandes JB, Staerk D.
In this study, HPLC-PDA-HRMS-SPE-NMR data were used for initial analysis of the CH<sub>2</sub>Cl<sub>2</sub> fraction of an EtOH extract of the leaves of <i>Picramnia glazioviana</i>. The HRMS, UV, and NMR data obtained from the HPLC-PDA-HRMS-SPE-NMR analysis were used to direct semipreparative HPLC isolation toward nortriterpenoids, which resulted in the isolation of 18 new and highly oxygenated nortriterpenoids (<b>1</b>-<b>3</b>, <b>5</b>-<b>10</b>, <b>12</b>-<b>19</b>, and <b>21</b>), named picravianes C-T. Their structures were determined on the basis of analysis of UV, HRMS, and 2D NMR spectroscopic data, including determination of the relative configuration on the basis of coupling pattern analysis and nuclear Overhauser effect correlations. The absolute configurations of compounds <b>7</b>, <b>9</b>, <b>10</b>, <b>14</b>, <b>15</b>, <b>17</b>, <b>18</b>, <b>19</b>, and <b>21</b> were assigned using electronic circular dichroism data, and the cytotoxicity of compounds <b>6</b>, <b>10</b>, <b>14</b>, <b>16</b>, <b>17</b>, <b>18</b>, <b>19</b>, and <b>21</b> was evaluated against MDA-MB-231 triple-negative breast cancer, SKBR-3 Her2-overexpressing breast cancer, and A549 lung cancer cells lines. The isolated compounds contain a hitherto undescribed modification of the terminal backbone and/or E-ring, and a possible biosynthetic pathway for their formation is proposed.