Stilbene derivatives from <i>Hydrangea davidii</i> and their antimalarial activities

For the purpose to better understand the antimalarial substance from <i>Hydrangea davidii</i>, two new stilbene derivatives, hydavidioside A (<b>1</b>) and hydavidioside B (<b>2</b>), and a new natural stilbene derivative, hydavidioside C (<b>3</b>), together with fifteen known analogous compounds (<b>4-18</b>), were isolated and identified. All the compounds were obtained from this plant for the first time, and part of them were examined for their antimalarial activity. Compounds <b>3</b>, <b>5</b>, <b>12</b>, <b>14</b>, <b>15</b>, and <b>16</b> showed significant antimalarial activities against <i>Plasmodium falciparum</i> 3D7 with IC₅₀ values of 0.52, 0.03, 14.78, 1.26, 7.33, and 4.33 μM, respectively. Moreover, <b>5</b> showed broad-spectrum efficacy against both <i>P. falciparum</i> Dd2 and <i>P. falciparum</i> 803 with IC₅₀ values of 0.046 and 0.057 μM. To explore <b>5'</b>s active mechanism, an in silico molecular docking approach was employed. In addition, the possible biogenetic pathways and the antimalarial structure-activity relationship for the isolated stilbene derivatives <b>1-18</b> were briefly discussed.