<p>The chemosystematic relationship of four <i>Diplotaxis</i> species; <i>Diplotaxis acris</i>, <i>Diplotaxis erucoides</i>, <i>Diplotaxis harra</i> and <i>Diplotaxis muralis</i> were surveyed from the flavonoids point of view. These species were found to produce 33 flavonoids (7 flavones and 26 flavonols), including 11 compounds were isolated in the present study from <i>D. acris</i>. Among them, seven flavonoids were identified for the first time; luteolin (<b>4</b>), kaempferol (<b>8</b>), kaempferol 3-<i>O</i>-<i>β</i>-glucopyranoside-7-<i>O</i>-<i>α</i>-rhamnopyranoside (<b>13</b>), quercetin 3-<i>O</i>-<i>β</i>-glucopyranoside (<b>16</b>), quercetin 7-<i>O</i>-<i>β</i>-glucopyranoside (<b>20</b>), isorhamnetin (<b>22</b>) and isorhamnetin 3-<i>O</i>-<i>β</i>-glucopyranoside-7-<i>O</i>-<i>α</i>-rhamnopyranoside (<b>32</b>). Their structures were recognized on the basis of chemical and spectroscopic techniques (1D & 2D NMR, UV, EI & ESI/MS). The isolated flavonoids may provide useful taxonomic characters at the infraspecific levels of classification where the flavonoid profile of <i>D. acris</i> and <i>D. harra</i> is similar and different from the other species.</p
