| Summary: | The chemical diversity of the approximately 1,200 natural products isolated from red algae of the genus <i>Laurencia</i>, in combination with the wide range of their biological activities, have placed species of <i>Laurencia</i> in the spotlight of marine chemists’ attention for over 60 years. The chemical investigation of the organic (CH<sub>2</sub>Cl<sub>2</sub>/MeOH) extracts of <i>Laurencia microcladia</i> and <i>Laurencia obtusa</i>, both collected off the coasts of Tinos island in the Aegean Sea, resulted in the isolation of 32 secondary metabolites, including 23 C<sub>15</sub> acetogenins (<b>1</b>–<b>23</b>), 7 sesquiterpenes (<b>24</b>–<b>30</b>) and 2 diterpenes (<b>31</b> and <b>32</b>). Among them, six new C<sub>15</sub> acetogenins, namely 10-acetyl-sagonenyne (<b>2</b>), <i>cis</i>-sagonenyne (<b>3</b>), <i>trans</i>-thuwalenyne C (<b>4</b>), tinosallene A (<b>11</b>), tinosallene B (<b>12</b>) and obtusallene XI (<b>17</b>), were identified and their structures were elucidated by extensive analysis of their spectroscopic data. Compounds <b>1</b>–<b>3</b>, <b>5</b>–<b>11</b>, <b>13</b> and <b>15</b>–<b>32</b> were evaluated for their antibacterial activity against <i>Staphylococcus aureus</i> and <i>Escherichia coli</i>.
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